%% =====================================================================
%% Licensed under the Apache License, Version 2.0 (the "License"); you may
%% not use this file except in compliance with the License. You may obtain
%% a copy of the License at <http://www.apache.org/licenses/LICENSE-2.0>
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% Alternatively, you may use this file under the terms of the GNU Lesser
%% General Public License (the "LGPL") as published by the Free Software
%% Foundation; either version 2.1, or (at your option) any later version.
%% If you wish to allow use of your version of this file only under the
%% terms of the LGPL, you should delete the provisions above and replace
%% them with the notice and other provisions required by the LGPL; see
%% <http://www.gnu.org/licenses/>. If you do not delete the provisions
%% above, a recipient may use your version of this file under the terms of
%% either the Apache License or the LGPL.
%%
%% @copyright 1997-2006 Richard Carlsson
%% @author Richard Carlsson <carlsson.richard@gmail.com>
%% @end
%% =====================================================================

%% @doc Abstract Erlang syntax trees.
%%
%% This module defines an abstract data type for representing Erlang
%% source code as syntax trees, in a way that is backwards compatible
%% with the data structures created by the Erlang standard library
%% parser module `erl_parse' (often referred to as "parse
%% trees", which is a bit of a misnomer). This means that all
%% `erl_parse' trees are valid abstract syntax trees, but the
%% reverse is not true: abstract syntax trees can in general not be used
%% as input to functions expecting an `erl_parse' tree.
%% However, as long as an abstract syntax tree represents a correct
%% Erlang program, the function {@link revert/1} should be able to
%% transform it to the corresponding `erl_parse'
%% representation.
%%
%% A recommended starting point for the first-time user is the documentation
%% of the {@link syntaxTree()} data type, and the function {@link type/1}.
%%
%% == NOTES: ==
%%
%% This module deals with the composition and decomposition of
%% <em>syntactic</em> entities (as opposed to semantic ones); its
%% purpose is to hide all direct references to the data structures used
%% to represent these entities. With few exceptions, the functions in
%% this module perform no semantic interpretation of their inputs, and
%% in general, the user is assumed to pass type-correct arguments - if
%% this is not done, the effects are not defined.
%%
%% With the exception of the {@link erl_parse()} data structures,
%% the internal representations of abstract syntax trees are subject to
%% change without notice, and should not be documented outside this
%% module. Furthermore, we do not give any guarantees on how an abstract
%% syntax tree may or may not be represented, <em>with the following
%% exceptions</em>: no syntax tree is represented by a single atom, such
%% as `none', by a list constructor `[X | Y]', or
%% by the empty list `[]'. This can be relied on when writing
%% functions that operate on syntax trees.

%% @type syntaxTree(). An abstract syntax tree. The {@link erl_parse()}
%% "parse tree" representation is a proper subset of the `syntaxTree()'
%% representation.
%%
%% Every abstract syntax tree node has a <em>type</em>, given by the
%% function {@link type/1}. Each node also has associated
%% <em>attributes</em>; see {@link get_attrs/1} for details. The functions
%% {@link make_tree/2} and {@link subtrees/1} are generic
%% constructor/decomposition functions for abstract syntax trees. The
%% functions {@link abstract/1} and {@link concrete/1} convert between
%% constant Erlang terms and their syntactic representations. The set of
%% syntax tree nodes is extensible through the {@link tree/2} function.
%%
%% A syntax tree can be transformed to the {@link erl_parse()}
%% representation with the {@link revert/1} function.

-module(erl_syntax).
-moduledoc """
Abstract Erlang syntax trees.

This module defines an abstract data type for representing Erlang source code as
syntax trees, in a way that is backwards compatible with the data structures
created by the Erlang standard library parser module `erl_parse` (often referred
to as "parse trees", which is a bit of a misnomer). This means that all
`erl_parse` trees are valid abstract syntax trees, but the reverse is not true:
abstract syntax trees can in general not be used as input to functions expecting
an `erl_parse` tree. However, as long as an abstract syntax tree represents a
correct Erlang program, the function `revert/1` should be able to transform it
to the corresponding `erl_parse` representation.

A recommended starting point for the first-time user is the documentation of the
[`syntaxTree()`](`t:syntaxTree/0`) data type, and the function `type/1`.

### NOTES:

This module deals with the composition and decomposition of _syntactic_ entities
(as opposed to semantic ones); its purpose is to hide all direct references to
the data structures used to represent these entities. With few exceptions, the
functions in this module perform no semantic interpretation of their inputs, and
in general, the user is assumed to pass type-correct arguments - if this is not
done, the effects are not defined.

With the exception of the [`erl_parse()`](`t:erl_parse/0`) data structures, the
internal representations of abstract syntax trees are subject to change without
notice, and should not be documented outside this module. Furthermore, we do not
give any guarantees on how an abstract syntax tree may or may not be
represented, _with the following exceptions_: no syntax tree is represented by a
single atom, such as `none`, by a list constructor `[X | Y]`, or by the empty
list `[]`. This can be relied on when writing functions that operate on syntax
trees.
""".

-export([type/1,
	 is_leaf/1,
	 is_form/1,
	 is_literal/1,
	 abstract/1,
	 concrete/1,
	 revert/1,
	 revert_forms/1,
	 subtrees/1,
	 make_tree/2,
	 update_tree/2,
	 meta/1,

	 get_pos/1,
	 set_pos/2,
	 copy_pos/2,
	 get_precomments/1,
	 set_precomments/2,
	 add_precomments/2,
	 get_postcomments/1,
	 set_postcomments/2,
	 add_postcomments/2,
	 has_comments/1,
	 remove_comments/1,
	 copy_comments/2,
	 join_comments/2,
	 get_ann/1,
	 set_ann/2,
	 add_ann/2,
	 copy_ann/2,
	 get_attrs/1,
	 set_attrs/2,
	 copy_attrs/2,

	 flatten_form_list/1,
	 cons/2,
	 list_head/1,
	 list_tail/1,
	 is_list_skeleton/1,
	 is_proper_list/1,
	 list_elements/1,
	 list_length/1,
	 normalize_list/1,
	 compact_list/1,

         annotated_type/2,
         annotated_type_name/1,
         annotated_type_body/1,
	 application/2,
	 application/3,
	 application_arguments/1,
	 application_operator/1,
	 arity_qualifier/2,
	 arity_qualifier_argument/1,
	 arity_qualifier_body/1,
	 atom/1,
	 is_atom/2,
	 atom_value/1,
	 atom_literal/1,
         atom_literal/2,
	 atom_name/1,
	 attribute/1,
	 attribute/2,
	 attribute_arguments/1,
	 attribute_name/1,
	 binary/1,
	 binary_comp/2,
	 binary_comp_template/1,
	 binary_comp_body/1,
	 binary_field/1,
	 binary_field/2,
	 binary_field/3,
	 binary_field_body/1,
	 binary_field_types/1,
	 binary_field_size/1,
	 binary_fields/1,
	 binary_generator/2,
	 binary_generator_body/1,
	 binary_generator_pattern/1,
         bitstring_type/2,
         bitstring_type_m/1,
         bitstring_type_n/1,
	 block_expr/1,
	 block_expr_body/1,
	 case_expr/2,
	 case_expr_argument/1,
	 case_expr_clauses/1,
	 catch_expr/1,
	 catch_expr_body/1,
	 char/1,
	 is_char/2,
	 char_value/1,
	 char_literal/1,
	 char_literal/2,
	 clause/2,
	 clause/3,
	 clause_body/1,
	 clause_guard/1,
	 clause_patterns/1,
	 comment/1,
	 comment/2,
	 comment_padding/1,
	 comment_text/1,
	 conjunction/1,
	 conjunction_body/1,
         constrained_function_type/2,
         constrained_function_type_body/1,
         constrained_function_type_argument/1,
         constraint/2,
         constraint_argument/1,
         constraint_body/1,
	 disjunction/1,
	 disjunction_body/1,
         else_expr/1,
         else_expr_clauses/1,
	 eof_marker/0,
	 error_marker/1,
	 error_marker_info/1,
	 float/1,
	 float_value/1,
	 float_literal/1,
	 form_list/1,
	 form_list_elements/1,
	 fun_expr/1,
	 fun_expr_arity/1,
	 fun_expr_clauses/1,
         fun_type/0,
	 function/2,
	 function_arity/1,
	 function_clauses/1,
	 function_name/1,
         function_type/1,
         function_type/2,
         function_type_arguments/1,
         function_type_return/1,
	 generator/2,
	 generator_body/1,
	 generator_pattern/1,
	 if_expr/1,
	 if_expr_clauses/1,
	 implicit_fun/1,
	 implicit_fun/2,
	 implicit_fun/3,
	 implicit_fun_name/1,
	 infix_expr/3,
	 infix_expr_left/1,
	 infix_expr_operator/1,
	 infix_expr_right/1,
	 integer/1,
	 is_integer/2,
	 integer_value/1,
	 integer_literal/1,
         integer_range_type/2,
         integer_range_type_low/1,
         integer_range_type_high/1,
	 list/1,
	 list/2,
	 list_comp/2,
	 list_comp_body/1,
	 list_comp_template/1,
	 list_prefix/1,
	 list_suffix/1,
	 macro/1,
	 macro/2,
	 macro_arguments/1,
	 macro_name/1,
         map_comp/2,
         map_comp_template/1,
         map_comp_body/1,
         map_expr/1,
         map_expr/2,
         map_expr_argument/1,
         map_expr_fields/1,
         map_field_assoc/2,
         map_field_assoc_name/1,
         map_field_assoc_value/1,
         map_field_exact/2,
         map_field_exact_name/1,
         map_field_exact_value/1,
         map_generator/2,
         map_generator_body/1,
         map_generator_pattern/1,
         map_type/0,
         map_type/1,
         map_type_fields/1,
         map_type_assoc/2,
         map_type_assoc_name/1,
         map_type_assoc_value/1,
         map_type_exact/2,
         map_type_exact_name/1,
         map_type_exact_value/1,
	 match_expr/2,
	 match_expr_body/1,
	 match_expr_pattern/1,
         maybe_expr/1,
         maybe_expr/2,
         maybe_expr_body/1,
         maybe_expr_else/1,
         maybe_match_expr/2,
         maybe_match_expr_pattern/1,
         maybe_match_expr_body/1,
	 module_qualifier/2,
	 module_qualifier_argument/1,
	 module_qualifier_body/1,
	 named_fun_expr/2,
	 named_fun_expr_arity/1,
	 named_fun_expr_clauses/1,
	 named_fun_expr_name/1,
	 nil/0,
	 operator/1,
	 operator_literal/1,
	 operator_name/1,
	 parentheses/1,
	 parentheses_body/1,
	 prefix_expr/2,
	 prefix_expr_argument/1,
	 prefix_expr_operator/1,
	 receive_expr/1,
	 receive_expr/3,
	 receive_expr_action/1,
	 receive_expr_clauses/1,
	 receive_expr_timeout/1,
	 record_access/3,
	 record_access_argument/1,
	 record_access_field/1,
	 record_access_type/1,
	 record_expr/2,
	 record_expr/3,
	 record_expr_argument/1,
	 record_expr_fields/1,
	 record_expr_type/1,
	 record_field/1,
	 record_field/2,
	 record_field_name/1,
	 record_field_value/1,
	 record_index_expr/2,
	 record_index_expr_field/1,
	 record_index_expr_type/1,
         record_type/2,
         record_type_name/1,
         record_type_fields/1,
         record_type_field/2,
         record_type_field_name/1,
         record_type_field_type/1,
	 size_qualifier/2,
	 size_qualifier_argument/1,
	 size_qualifier_body/1,
	 string/1,
	 is_string/2,
	 string_value/1,
	 string_literal/1,
	 string_literal/2,
	 text/1,
	 text_string/1,
	 try_expr/2,
	 try_expr/3,
	 try_expr/4,
	 try_after_expr/2,
	 try_expr_body/1,
	 try_expr_clauses/1,
	 try_expr_handlers/1,
	 try_expr_after/1,
         tuple_type/0,
         tuple_type/1,
         tuple_type_elements/1,
         type_application/2,
         type_application/3,
         type_application_name/1,
         type_application_arguments/1,
         type_union/1,
         type_union_types/1,
	 typed_record_field/2,
	 typed_record_field_body/1,
         typed_record_field_type/1,
	 class_qualifier/2,
	 class_qualifier/3,
	 class_qualifier_argument/1,
	 class_qualifier_body/1,
	 class_qualifier_stacktrace/1,
	 tuple/1,
	 tuple_elements/1,
	 tuple_size/1,
	 underscore/0,
         user_type_application/2,
         user_type_application_name/1,
         user_type_application_arguments/1,
	 variable/1,
	 variable_name/1,
	 variable_literal/1,
	 warning_marker/1,
	 warning_marker_info/1,

	 tree/1,
	 tree/2,
	 data/1,
	 is_tree/1]).

-export_type([forms/0, syntaxTree/0, syntaxTreeAttributes/0, padding/0, annotation_or_location/0]).

%% =====================================================================
%% IMPLEMENTATION NOTES:
%%
%% All nodes are represented by tuples of arity 2 or greater, whose
%% first element is an atom which uniquely identifies the type of the
%% node. (In the backwards-compatible representation, the
%% interpretation is also often dependent on the context; the second
%% element generally holds the annotation (see module {@link
%% //stdlib/erl_anno} for details) which includes the position
%% information - with a couple of exceptions; see `get_pos' and
%% `set_pos' for details.) In the documentation of this module, `Pos'
%% is the annotation associated with a node. No assumptions are made
%% in this module regarding the format or interpretation of the
%% annotations. Use module erl_anno to inspect and modify annotations.
%% In particular, use {@link //stdlib/erl_anno:location/1} to get the
%% position information, and use {@link
%% //stdlib/erl_anno:set_location/2} or {@link
%% //stdlib/erl_anno:set_line/2} to change the position information.
%% When a syntax tree node is constructed, its associated position is
%% by default set to the integer zero.
%% =====================================================================

-define(NO_UNUSED, true).

%% =====================================================================
%% Declarations of globally used internal data structures
%% =====================================================================

%% `com' records are used to hold comment information attached to a
%% syntax tree node or a wrapper structure.
%%
%% #com{pre :: Pre, post :: Post}
%%
%%	Pre = Post = [Com]
%%	Com = syntaxTree()
%%
%%	type(Com) = comment

-record(com, {pre  = [] :: [syntaxTree()],
	      post = [] :: [syntaxTree()]}).

%% `attr' records store node attributes as an aggregate.
%%
%% #attr{pos :: Pos, ann :: Ann, com :: Comments}
%%
%%	Pos = term()
%%	Ann = [term()]
%%	Comments = none | #com{}
%%
%% where `Pos' `Ann' and `Comments' are the corresponding values of a
%% `tree' or `wrapper' record.

-record(attr, {pos = erl_anno:new(0) :: term(),
	       ann = []   :: [term()],
	       com = none :: 'none' | #com{}}).
-type syntaxTreeAttributes() :: #attr{}.

%% `tree' records represent new-form syntax tree nodes.
%%
%% Tree = #tree{type :: Type, attr :: Attr, data :: Data}
%%
%%	Type = atom()
%%	Attr = #attr{}
%%	Data = term()
%%
%%	is_tree(Tree) = true

-record(tree, {type           :: atom(),
	       attr = #attr{} :: #attr{},
	       data           :: term()}).
-type tree() :: #tree{}.

%% `wrapper' records are used for attaching new-form node information to
%% `erl_parse' trees.
%%
%% Wrapper = #wrapper{type :: Type, attr :: Attr, tree :: ParseTree}
%%
%%	Type = atom()
%%	Attr = #attr{}
%%	ParseTree = term()
%%
%%	is_tree(Wrapper) = false

-record(wrapper, {type           :: atom(),
		  attr = #attr{} :: #attr{},
		  tree           :: erl_parse()}).
-type wrapper() :: #wrapper{}.

%% =====================================================================

-type syntaxTree() :: tree() | wrapper() | erl_parse().

-type erl_parse() :: erl_parse:abstract_clause()
                   | erl_parse:abstract_expr()
                   | erl_parse:abstract_form()
                   | erl_parse:abstract_type()
                   | erl_parse:form_info()
                   | erl_parse:af_binelement(term())
                   | erl_parse:af_generator()
                   | erl_parse:af_remote_function().

%% The representation built by the Erlang standard library parser
%% `erl_parse'. This is a subset of the {@link syntaxTree()} type.

%% =====================================================================
%%
%%			Exported functions
%%
%% =====================================================================


%% =====================================================================
%% @doc Returns the type tag of `Node'. If `Node'
%% does not represent a syntax tree, evaluation fails with reason
%% `badarg'. Node types currently defined by this module are:
%%
%% <center><table border="1">
%%  <tr>
%%   <td>application</td>
%%   <td>annotated_type</td>
%%   <td>arity_qualifier</td>
%%   <td>atom</td>
%%  </tr><tr>
%%   <td>attribute</td>
%%   <td>binary</td>
%%   <td>binary_field</td>
%%   <td>bitstring_type</td>
%%  </tr><tr>
%%   <td>block_expr</td>
%%   <td>case_expr</td>
%%   <td>catch_expr</td>
%%   <td>char</td>
%%  </tr><tr>
%%   <td>class_qualifier</td>
%%   <td>clause</td>
%%   <td>comment</td>
%%   <td>conjunction</td>
%%  </tr><tr>
%%   <td>constrained_function_type</td>
%%   <td>constraint</td>
%%   <td>disjunction</td>
%%  </tr><tr>
%%   <td>else_expr</td>
%%   <td>eof_marker</td>
%%   <td>error_marker</td>
%%  </tr><tr>
%%   <td>float</td>
%%   <td>form_list</td>
%%   <td>fun_expr</td>
%%   <td>fun_type</td>
%%   <td>function</td>
%%   <td>function_type</td>
%%   <td>generator</td>
%%  </tr><tr>
%%   <td>if_expr</td>
%%   <td>implicit_fun</td>
%%   <td>infix_expr</td>
%%   <td>integer</td>
%%  </tr><tr>
%%   <td>integer_range_type</td>
%%   <td>list</td>
%%   <td>list_comp</td>
%%   <td>macro</td>
%%  </tr><tr>
%%   <td>map_expr</td>
%%   <td>map_field_assoc</td>
%%   <td>map_field_exact</td>
%%   <td>map_type</td>
%%  </tr><tr>
%%   <td>map_type_assoc</td>
%%   <td>map_type_exact</td>
%%   <td>match_expr</td>
%%  </tr><tr>
%%   <td>maybe_expr</td>
%%   <td>maybe_match_expr</td>
%%   <td>module_qualifier</td>
%%  </tr><tr>
%%   <td>named_fun_expr</td>
%%   <td>nil</td>
%%   <td>operator</td>
%%   <td>parentheses</td>
%%  </tr><tr>
%%   <td>prefix_expr</td>
%%   <td>receive_expr</td>
%%   <td>record_access</td>
%%   <td>record_expr</td>
%%  </tr><tr>
%%   <td>record_field</td>
%%   <td>record_index_expr</td>
%%   <td>record_type</td>
%%   <td>record_type_field</td>
%%  </tr><tr>
%%   <td>size_qualifier</td>
%%   <td>string</td>
%%   <td>text</td>
%%   <td>try_expr</td>
%%  </tr><tr>
%%   <td>tuple</td>
%%   <td>tuple_type</td>
%%   <td>typed_record_field</td>
%%   <td>type_application</td>
%%  </tr><tr>
%%   <td>type_union</td>
%%   <td>underscore</td>
%%   <td>user_type_application</td>
%%   <td>variable</td>
%%  </tr><tr>
%%   <td>warning_marker</td>
%%  </tr>
%% </table></center>
%%
%% The user may (for special purposes) create additional nodes
%% with other type tags, using the {@link tree/2} function.
%%
%% Note: The primary constructor functions for a node type should
%% always have the same name as the node type itself.
%%
%% @see tree/2
%% @see annotated_type/2
%% @see application/3
%% @see arity_qualifier/2
%% @see atom/1
%% @see attribute/2
%% @see binary/1
%% @see binary_field/2
%% @see bitstring_type/2
%% @see block_expr/1
%% @see case_expr/2
%% @see catch_expr/1
%% @see char/1
%% @see class_qualifier/2
%% @see clause/3
%% @see comment/2
%% @see conjunction/1
%% @see constrained_function_type/2
%% @see constraint/2
%% @see disjunction/1
%% @see else_expr/1
%% @see eof_marker/0
%% @see error_marker/1
%% @see float/1
%% @see form_list/1
%% @see fun_expr/1
%% @see fun_type/0
%% @see function/2
%% @see function_type/1
%% @see function_type/2
%% @see generator/2
%% @see if_expr/1
%% @see implicit_fun/2
%% @see infix_expr/3
%% @see integer/1
%% @see integer_range_type/2
%% @see list/2
%% @see list_comp/2
%% @see macro/2
%% @see map_expr/2
%% @see map_field_assoc/2
%% @see map_field_exact/2
%% @see map_type/0
%% @see map_type/1
%% @see map_type_assoc/2
%% @see map_type_exact/2
%% @see match_expr/2
%% @see maybe_expr/1
%% @see maybe_expr/2
%% @see maybe_match_expr/2
%% @see module_qualifier/2
%% @see named_fun_expr/2
%% @see nil/0
%% @see operator/1
%% @see parentheses/1
%% @see prefix_expr/2
%% @see receive_expr/3
%% @see record_access/3
%% @see record_expr/2
%% @see record_field/2
%% @see record_index_expr/2
%% @see record_type/2
%% @see record_type_field/2
%% @see size_qualifier/2
%% @see string/1
%% @see text/1
%% @see try_expr/3
%% @see tuple/1
%% @see tuple_type/0
%% @see tuple_type/1
%% @see typed_record_field/2
%% @see type_application/2
%% @see type_union/1
%% @see underscore/0
%% @see user_type_application/2
%% @see variable/1
%% @see warning_marker/1

-doc """
Returns the type tag of `Node`. If `Node` does not represent a syntax tree,
evaluation fails with reason `badarg`. Node types currently defined by this
module are:

<center><table><tr><td>application</td><td>annotated_type</td><td>arity_qualifier</td><td>atom</td></tr><tr><td>attribute</td><td>binary</td><td>binary_field</td><td>bitstring_type</td></tr><tr><td>block_expr</td><td>case_expr</td><td>catch_expr</td><td>char</td></tr><tr><td>class_qualifier</td><td>clause</td><td>comment</td><td>conjunction</td></tr><tr><td>constrained_function_type</td><td>constraint</td><td>disjunction</td></tr><tr><td>else_expr</td><td>eof_marker</td><td>error_marker</td></tr><tr><td>float</td><td>form_list</td><td>fun_expr</td><td>fun_type</td><td>function</td><td>function_type</td><td>generator</td></tr><tr><td>if_expr</td><td>implicit_fun</td><td>infix_expr</td><td>integer</td></tr><tr><td>integer_range_type</td><td>list</td><td>list_comp</td><td>macro</td></tr><tr><td>map_expr</td><td>map_field_assoc</td><td>map_field_exact</td><td>map_type</td></tr><tr><td>map_type_assoc</td><td>map_type_exact</td><td>match_expr</td></tr><tr><td>maybe_expr</td><td>maybe_match_expr</td><td>module_qualifier</td></tr><tr><td>named_fun_expr</td><td>nil</td><td>operator</td><td>parentheses</td></tr><tr><td>prefix_expr</td><td>receive_expr</td><td>record_access</td><td>record_expr</td></tr><tr><td>record_field</td><td>record_index_expr</td><td>record_type</td><td>record_type_field</td></tr><tr><td>size_qualifier</td><td>string</td><td>text</td><td>try_expr</td></tr><tr><td>tuple</td><td>tuple_type</td><td>typed_record_field</td><td>type_application</td></tr><tr><td>type_union</td><td>underscore</td><td>user_type_application</td><td>variable</td></tr><tr><td>warning_marker</td></tr></table></center>

The user may (for special purposes) create additional nodes with other type
tags, using the `tree/2` function.

Note: The primary constructor functions for a node type should always have the
same name as the node type itself.

_See also: _`annotated_type/2`, `application/3`, `arity_qualifier/2`, `atom/1`,
`attribute/2`, `binary/1`, `binary_field/2`, `bitstring_type/2`, `block_expr/1`,
`case_expr/2`, `catch_expr/1`, `char/1`, `class_qualifier/2`, `clause/3`,
`comment/2`, `conjunction/1`, `constrained_function_type/2`, `constraint/2`,
`disjunction/1`, `else_expr/1`, `eof_marker/0`, `error_marker/1`, `float/1`,
`form_list/1`, `fun_expr/1`, `fun_type/0`, `function/2`, `function_type/1`,
`function_type/2`, `generator/2`, `if_expr/1`, `implicit_fun/2`, `infix_expr/3`,
`integer/1`, `integer_range_type/2`, `list/2`, `list_comp/2`, `macro/2`,
`map_expr/2`, `map_field_assoc/2`, `map_field_exact/2`, `map_type/0`,
`map_type/1`, `map_type_assoc/2`, `map_type_exact/2`, `match_expr/2`,
`maybe_expr/1`, `maybe_expr/2`, `maybe_match_expr/2`, `module_qualifier/2`,
`named_fun_expr/2`, `nil/0`, `operator/1`, `parentheses/1`, `prefix_expr/2`,
`receive_expr/3`, `record_access/3`, `record_expr/2`, `record_field/2`,
`record_index_expr/2`, `record_type/2`, `record_type_field/2`,
`size_qualifier/2`, `string/1`, `text/1`, `tree/2`, `try_expr/3`, `tuple/1`,
`tuple_type/0`, `tuple_type/1`, `type_application/2`, `type_union/1`,
`typed_record_field/2`, `underscore/0`, `user_type_application/2`, `variable/1`,
`warning_marker/1`.
""".
-spec type(syntaxTree()) -> atom().

type(#tree{type = T}) ->
    T;
type(#wrapper{type = T}) ->
    T;
type(Node) ->
    %% Check for `erl_parse'-compatible nodes, and otherwise fail.
    case Node of
	%% Leaf types
	{atom, _, _} -> atom;
	{char, _, _} -> char;
	{float, _, _} -> float;
	{integer, _, _} -> integer;
	{nil, _} -> nil;
	{string, _, _} -> string;
	{var, _, Name} ->
	    if Name =:= '_' -> underscore;
	       true -> variable
	    end;
	{error, _} -> error_marker;
	{warning, _} -> warning_marker;
	{eof, _} -> eof_marker;

	%% Composite types
	{'case', _, _, _} -> case_expr;
	{'catch', _, _} -> catch_expr;
	{'fun', _, {clauses, _}} -> fun_expr;
	{named_fun, _, _, _} -> named_fun_expr;
	{'fun', _, {function, _, _}} -> implicit_fun;
	{'fun', _, {function, _, _, _}} -> implicit_fun;
	{'if', _, _} -> if_expr;
        {'maybe', _, _} -> maybe_expr;
        {'maybe', _, _, _} -> maybe_expr;
        {'else', _, _} -> else_expr;
	{'receive', _, _, _, _} -> receive_expr;
	{'receive', _, _} -> receive_expr;
	{attribute, _, _, _} -> attribute;
	{bin, _, _} -> binary;
	{bin_element, _, _, _, _} -> binary_field;
	{block, _, _} -> block_expr;
	{call, _, _, _} -> application;
	{clause, _, _, _, _} -> clause;
	{cons, _, _, _} -> list;
	{function, _, _, _, _} -> function;
	{b_generate, _, _, _} -> binary_generator;
	{generate, _, _, _} -> generator;
	{m_generate, _, _, _} -> map_generator;
	{lc, _, _, _} -> list_comp;
	{bc, _, _, _} -> binary_comp;
	{mc, _, _, _} -> map_comp;
	{match, _, _, _} -> match_expr;
        {map, _, _, _} -> map_expr;
        {map, _, _} -> map_expr;
        {map_field_assoc, _, _, _} -> map_field_assoc;
        {map_field_exact, _, _, _} -> map_field_exact;
        {maybe_match, _, _, _} -> maybe_match_expr;
	{op, _, _, _, _} -> infix_expr;
	{op, _, _, _} -> prefix_expr;
	{record, _, _, _, _} -> record_expr;
	{record, _, _, _} -> record_expr;
	{record_field, _, _, _, _} -> record_access;
	{record_index, _, _, _} -> record_index_expr;
	{remote, _, _, _} -> module_qualifier;
	{'try', _, _, _, _, _} -> try_expr;
	{tuple, _, _} -> tuple;

        %% Type types
        {ann_type, _, _} -> annotated_type;
        {remote_type, _, _} -> type_application;
        {type, _, binary, [_, _]} -> bitstring_type;
        {type, _, bounded_fun, [_, _]} -> constrained_function_type;
        {type, _, constraint, [_, _]} -> constraint;
        {type, _, 'fun', []} -> fun_type;
        {type, _, 'fun', [_, _]} -> function_type;
        {type, _, map, _} -> map_type;
        {type, _, map_field_assoc, _} -> map_type_assoc;
        {type, _, map_field_exact, _} -> map_type_exact;
        {type, _, record, _} -> record_type;
        {type, _, field_type, _} -> record_type_field;
        {type, _, range, _} -> integer_range_type;
        {type, _, tuple, _} -> tuple_type;
        {type, _, union, _} -> type_union;
        {type, _, _, _} -> type_application;
        {user_type, _, _, _} -> user_type_application;
	_ ->
	    erlang:error({badarg, Node})
    end.


%% =====================================================================
%% @doc Returns `true' if `Node' is a leaf node,
%% otherwise `false'. The currently recognised leaf node
%% types are:
%%
%% <center><table border="1">
%%  <tr>
%%   <td>`atom'</td>
%%   <td>`char'</td>
%%   <td>`comment'</td>
%%   <td>`eof_marker'</td>
%%   <td>`error_marker'</td>
%%  </tr><tr>
%%   <td>`float'</td>
%%   <td>`fun_type'</td>
%%   <td>`integer'</td>
%%   <td>`nil'</td>
%%   <td>`operator'</td>
%%   <td>`string'</td>
%%  </tr><tr>
%%   <td>`text'</td>
%%   <td>`underscore'</td>
%%   <td>`variable'</td>
%%   <td>`warning_marker'</td>
%%  </tr>
%% </table></center>
%%
%% A node of type `map_expr' is a leaf node if and only if it has no
%% argument and no fields.
%% A node of type `map_type' is a leaf node if and only if it has no
%% fields (`any_size').
%% A node of type `tuple' is a leaf node if and only if its arity is zero.
%% A node of type `tuple_type' is a leaf node if and only if it has no
%% elements (`any_size').
%%
%% Note: not all literals are leaf nodes, and vice versa. E.g.,
%% tuples with nonzero arity and nonempty lists may be literals, but are
%% not leaf nodes. Variables, on the other hand, are leaf nodes but not
%% literals.
%%
%% @see type/1
%% @see is_literal/1

-doc """
Returns `true` if `Node` is a leaf node, otherwise `false`. The currently
recognised leaf node types are:

<center><table><tr><td>`atom`</td><td>`char`</td><td>`comment`</td><td>`eof_marker`</td><td>`error_marker`</td></tr><tr><td>`float`</td><td>`fun_type`</td><td>`integer`</td><td>`nil`</td><td>`operator`</td><td>`string`</td></tr><tr><td>`text`</td><td>`underscore`</td><td>`variable`</td><td>`warning_marker`</td></tr></table></center>

A node of type `map_expr` is a leaf node if and only if it has no argument and
no fields. A node of type `map_type` is a leaf node if and only if it has no
fields (`any_size`). A node of type `tuple` is a leaf node if and only if its
arity is zero. A node of type `tuple_type` is a leaf node if and only if it has
no elements (`any_size`).

Note: not all literals are leaf nodes, and vice versa. E.g., tuples with nonzero
arity and nonempty lists may be literals, but are not leaf nodes. Variables, on
the other hand, are leaf nodes but not literals.

_See also: _`is_literal/1`, `type/1`.
""".
-spec is_leaf(syntaxTree()) -> boolean().

is_leaf(Node) ->
    case type(Node) of
	atom -> true;
	char -> true;
	comment -> true;	% nonstandard type
	eof_marker -> true;
	error_marker -> true;
	float -> true;
        fun_type -> true;
	integer -> true;
	nil -> true;
	operator -> true;	% nonstandard type
	string -> true;
	text -> true;		% nonstandard type
	map_expr ->
	    map_expr_fields(Node) =:= [] andalso
	    map_expr_argument(Node) =:= none;
        map_type -> map_type_fields(Node) =:= any_size;
	tuple -> tuple_elements(Node) =:= [];
        tuple_type -> tuple_type_elements(Node) =:= any_size;
	underscore -> true;
	variable -> true;
	warning_marker -> true;
	_ -> false
    end.


%% =====================================================================
%% @doc Returns `true' if `Node' is a syntax tree
%% representing a so-called "source code form", otherwise
%% `false'. Forms are the Erlang source code units which,
%% placed in sequence, constitute an Erlang program. Current form types
%% are:
%%
%% <center><table border="1">
%%  <tr>
%%   <td>`attribute'</td>
%%   <td>`comment'</td>
%%   <td>`error_marker'</td>
%%   <td>`eof_marker'</td>
%%  </tr><tr>
%%   <td>`form_list'</td>
%%   <td>`function'</td>
%%   <td>`warning_marker'</td>
%%   <td>`text'</td>
%%  </tr>
%% </table></center>
%%
%% @see type/1
%% @see attribute/2
%% @see comment/2
%% @see eof_marker/0
%% @see error_marker/1
%% @see form_list/1
%% @see function/2
%% @see warning_marker/1

-doc """
Returns `true` if `Node` is a syntax tree representing a so-called "source code
form", otherwise `false`. Forms are the Erlang source code units which, placed
in sequence, constitute an Erlang program. Current form types are:

<center><table><tr><td>`attribute`</td><td>`comment`</td><td>`error_marker`</td><td>`eof_marker`</td></tr><tr><td>`form_list`</td><td>`function`</td><td>`warning_marker`</td><td>`text`</td></tr></table></center>

_See also: _`attribute/2`, `comment/2`, `eof_marker/0`, `error_marker/1`,
`form_list/1`, `function/2`, `type/1`, `warning_marker/1`.
""".
-spec is_form(syntaxTree()) -> boolean().

is_form(Node) ->
    case type(Node) of
	attribute -> true;
	comment -> true;
	function -> true;
	eof_marker -> true;
	error_marker -> true;
	form_list -> true;
	warning_marker -> true;
	text -> true;
	_ -> false
    end.


%% =====================================================================

%% @doc Returns the annotation (see {@link //stdlib/erl_anno})
%% associated with `Node'. By default, all new tree nodes have their
%% associated position information set to the integer zero. Use {@link
%% //stdlib/erl_anno:location/1} or {@link //stdlib/erl_anno:line/1}
%% to get the position information.
%%
%% @see set_pos/2
%% @see get_attrs/1

%% All `erl_parse' tree nodes are represented by tuples whose second
%% field is the annotation, *with the
%% exceptions of* `{error, ...}' (type `error_marker') and `{warning,
%% ...}' (type `warning_marker'), which only contain the associated location
%% *of the error descriptor*; this is all handled transparently
%% by `get_pos' and `set_pos'.

-type annotation_or_location() :: erl_anno:anno() | erl_anno:location().

-doc """
Returns the annotation (see [`//stdlib/erl_anno`](`m:erl_anno`)) associated with
`Node`. By default, all new tree nodes have their associated position
information set to the integer zero. Use
[`//stdlib/erl_anno:location/1`](`erl_anno:location/1`) or
[`//stdlib/erl_anno:line/1`](`erl_anno:line/1`) to get the position information.

_See also: _`get_attrs/1`, `set_pos/2`.
""".
-spec get_pos(syntaxTree()) -> annotation_or_location().

get_pos(#tree{attr = Attr}) ->
    Attr#attr.pos;
get_pos(#wrapper{attr = Attr}) ->
    Attr#attr.pos;
get_pos({error, {Pos, _, _}}) ->
    Pos;
get_pos({warning, {Pos, _, _}}) ->
    Pos;
get_pos(Node) ->
    %% Here, we assume that we have an `erl_parse' node with an
    %% annotation in element 2.
    element(2, Node).


%% =====================================================================
%% @doc Sets the position information of `Node' to `Pos'.
%%
%% @see get_pos/1
%% @see copy_pos/2

-doc """
Sets the position information of `Node` to `Pos`.

_See also: _`copy_pos/2`, `get_pos/1`.
""".
-spec set_pos(syntaxTree(), annotation_or_location()) -> syntaxTree().

set_pos(Node, Pos) ->
    case Node of
        #tree{attr = Attr} ->
            Node#tree{attr = Attr#attr{pos = Pos}};
        #wrapper{attr = Attr, tree = {error, {_, Module, Reason}}} ->
            Node#wrapper{attr = Attr#attr{pos = Pos}, tree = {error, {Pos, Module, Reason}}};
        #wrapper{attr = Attr, tree = {warning, {_, Module, Reason}}} ->
            Node#wrapper{attr = Attr#attr{pos = Pos}, tree = {warning, {Pos, Module, Reason}}};
        #wrapper{attr = Attr, tree = Tree} ->
            Node#wrapper{attr = Attr#attr{pos = Pos}, tree = setelement(2, Tree, Pos)};
        _ ->
            %% We then assume we have an `erl_parse' node, and create a
            %% wrapper around it to make things more uniform.
            set_pos(wrap(Node), Pos)
    end.


%% =====================================================================
%% @doc Copies the annotation from `Source' to `Target'.
%%
%% This is equivalent to `set_pos(Target,
%% get_pos(Source))', but potentially more efficient.
%%
%% @see get_pos/1
%% @see set_pos/2

-doc """
Copies the annotation from `Source` to `Target`.

This is equivalent to [`set_pos(Target, get_pos(Source))`](`set_pos/2`), but
potentially more efficient.

_See also: _`get_pos/1`, `set_pos/2`.
""".
-spec copy_pos(syntaxTree(), syntaxTree()) -> syntaxTree().

copy_pos(Source, Target) ->
    set_pos(Target, get_pos(Source)).


%% =====================================================================
%% `get_com' and `set_com' are for internal use only.

get_com(#tree{attr = Attr}) -> Attr#attr.com;
get_com(#wrapper{attr = Attr}) -> Attr#attr.com;
get_com(_) -> none.

set_com(Node, Com) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = Attr#attr{com = Com}};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = Attr#attr{com = Com}};
	_ ->
	    set_com(wrap(Node), Com)
    end.


%% =====================================================================
%% @doc Returns the associated pre-comments of a node. This is a
%% possibly empty list of abstract comments, in top-down textual order.
%% When the code is formatted, pre-comments are typically displayed
%% directly above the node. For example:
%% ```% Pre-comment of function
%%    foo(X) -> {bar, X}.'''
%%
%% If possible, the comment should be moved before any preceding
%% separator characters on the same line. E.g.:
%% ```foo([X | Xs]) ->
%%        % Pre-comment of 'bar(X)' node
%%        [bar(X) | foo(Xs)];
%%    ...'''
%% (where the comment is moved before the "`['").
%%
%% @see comment/2
%% @see set_precomments/2
%% @see get_postcomments/1
%% @see get_attrs/1

-doc """
Returns the associated pre-comments of a node. This is a possibly empty list of
abstract comments, in top-down textual order. When the code is formatted,
pre-comments are typically displayed directly above the node. For example:

```text
     % Pre-comment of function
     foo(X) -> {bar, X}.
```

If possible, the comment should be moved before any preceding separator
characters on the same line. E.g.:

```text
     foo([X | Xs]) ->
         % Pre-comment of 'bar(X)' node
         [bar(X) | foo(Xs)];
     ...
```

(where the comment is moved before the "`[`").

_See also: _`comment/2`, `get_attrs/1`, `get_postcomments/1`,
`set_precomments/2`.
""".
-spec get_precomments(syntaxTree()) -> [syntaxTree()].

get_precomments(#tree{attr = Attr}) -> get_precomments_1(Attr);
get_precomments(#wrapper{attr = Attr}) -> get_precomments_1(Attr);
get_precomments(_) -> [].

get_precomments_1(#attr{com = none}) -> [];
get_precomments_1(#attr{com = #com{pre = Cs}}) -> Cs.


%% =====================================================================
%% @doc Sets the pre-comments of `Node' to
%% `Comments'. `Comments' should be a possibly
%% empty list of abstract comments, in top-down textual order.
%%
%% @see comment/2
%% @see get_precomments/1
%% @see add_precomments/2
%% @see set_postcomments/2
%% @see copy_comments/2
%% @see remove_comments/1
%% @see join_comments/2

-doc """
Sets the pre-comments of `Node` to `Comments`. `Comments` should be a possibly
empty list of abstract comments, in top-down textual order.

_See also: _`add_precomments/2`, `comment/2`, `copy_comments/2`,
`get_precomments/1`, `join_comments/2`, `remove_comments/1`,
`set_postcomments/2`.
""".
-spec set_precomments(syntaxTree(), [syntaxTree()]) -> syntaxTree().

set_precomments(Node, Cs) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = set_precomments_1(Attr, Cs)};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = set_precomments_1(Attr, Cs)};
	_ ->
	    set_precomments(wrap(Node), Cs)
    end.

set_precomments_1(#attr{com = none} = Attr, Cs) ->
    Attr#attr{com = #com{pre = Cs}};
set_precomments_1(#attr{com = Com} = Attr, Cs) ->
    Attr#attr{com = Com#com{pre = Cs}}.


%% =====================================================================
%% @doc Appends `Comments' to the pre-comments of `Node'.
%%
%% Note: This is equivalent to `set_precomments(Node,
%% get_precomments(Node) ++ Comments)', but potentially more
%% efficient.
%%
%% @see comment/2
%% @see get_precomments/1
%% @see set_precomments/2
%% @see add_postcomments/2
%% @see join_comments/2

-doc """
Appends `Comments` to the pre-comments of `Node`.

Note: This is equivalent to
[`set_precomments(Node, get_precomments(Node) ++ Comments)`](`set_precomments/2`),
but potentially more efficient.

_See also: _`add_postcomments/2`, `comment/2`, `get_precomments/1`,
`join_comments/2`, `set_precomments/2`.
""".
-spec add_precomments([syntaxTree()], syntaxTree()) -> syntaxTree().

add_precomments(Cs, Node) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = add_precomments_1(Cs, Attr)};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = add_precomments_1(Cs, Attr)};
	_ ->
	    add_precomments(Cs, wrap(Node))
    end.

add_precomments_1(Cs, #attr{com = none} = Attr) ->
    Attr#attr{com = #com{pre = Cs}};
add_precomments_1(Cs, #attr{com = Com} = Attr) ->
    Attr#attr{com = Com#com{pre = Com#com.pre ++ Cs}}.


%% =====================================================================
%% @doc Returns the associated post-comments of a node. This is a
%% possibly empty list of abstract comments, in top-down textual order.
%% When the code is formatted, post-comments are typically displayed to
%% the right of and/or below the node. For example:
%% ```{foo, X, Y}     % Post-comment of tuple'''
%%
%% If possible, the comment should be moved past any following
%% separator characters on the same line, rather than placing the
%% separators on the following line. E.g.:
%% ```foo([X | Xs], Y) ->
%%        foo(Xs, bar(X));     % Post-comment of 'bar(X)' node
%%     ...'''
%% (where the comment is moved past the rightmost "`)'" and
%% the "`;'").
%%
%% @see comment/2
%% @see set_postcomments/2
%% @see get_precomments/1
%% @see get_attrs/1

-doc """
Returns the associated post-comments of a node. This is a possibly empty list of
abstract comments, in top-down textual order. When the code is formatted,
post-comments are typically displayed to the right of and/or below the node. For
example:

```text
     {foo, X, Y}     % Post-comment of tuple
```

If possible, the comment should be moved past any following separator characters
on the same line, rather than placing the separators on the following line.
E.g.:

```text
     foo([X | Xs], Y) ->
         foo(Xs, bar(X));     % Post-comment of 'bar(X)' node
      ...
```

(where the comment is moved past the rightmost "`)`" and the "`;`").

_See also: _`comment/2`, `get_attrs/1`, `get_precomments/1`,
`set_postcomments/2`.
""".
-spec get_postcomments(syntaxTree()) -> [syntaxTree()].

get_postcomments(#tree{attr = Attr}) -> get_postcomments_1(Attr);
get_postcomments(#wrapper{attr = Attr}) -> get_postcomments_1(Attr);
get_postcomments(_) -> [].

get_postcomments_1(#attr{com = none}) -> [];
get_postcomments_1(#attr{com = #com{post = Cs}}) -> Cs.


%% =====================================================================
%% @doc Sets the post-comments of `Node' to
%% `Comments'. `Comments' should be a possibly
%% empty list of abstract comments, in top-down textual order
%%
%% @see comment/2
%% @see get_postcomments/1
%% @see add_postcomments/2
%% @see set_precomments/2
%% @see copy_comments/2
%% @see remove_comments/1
%% @see join_comments/2

-doc """
Sets the post-comments of `Node` to `Comments`. `Comments` should be a possibly
empty list of abstract comments, in top-down textual order

_See also: _`add_postcomments/2`, `comment/2`, `copy_comments/2`,
`get_postcomments/1`, `join_comments/2`, `remove_comments/1`,
`set_precomments/2`.
""".
-spec set_postcomments(syntaxTree(), [syntaxTree()]) -> syntaxTree().

set_postcomments(Node, Cs) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = set_postcomments_1(Attr, Cs)};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = set_postcomments_1(Attr, Cs)};
	_ ->
	    set_postcomments(wrap(Node), Cs)
    end.

set_postcomments_1(#attr{com = none} = Attr, Cs) ->
    Attr#attr{com = #com{post = Cs}};
set_postcomments_1(#attr{com = Com} = Attr, Cs) ->
    Attr#attr{com = Com#com{post = Cs}}.


%% =====================================================================
%% @doc Appends `Comments' to the post-comments of `Node'.
%%
%% Note: This is equivalent to `set_postcomments(Node,
%% get_postcomments(Node) ++ Comments)', but potentially more
%% efficient.
%%
%% @see comment/2
%% @see get_postcomments/1
%% @see set_postcomments/2
%% @see add_precomments/2
%% @see join_comments/2

-doc """
Appends `Comments` to the post-comments of `Node`.

Note: This is equivalent to
[`set_postcomments(Node, get_postcomments(Node) ++ Comments)`](`set_postcomments/2`),
but potentially more efficient.

_See also: _`add_precomments/2`, `comment/2`, `get_postcomments/1`,
`join_comments/2`, `set_postcomments/2`.
""".
-spec add_postcomments([syntaxTree()], syntaxTree()) -> syntaxTree().

add_postcomments(Cs, Node) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = add_postcomments_1(Cs, Attr)};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = add_postcomments_1(Cs, Attr)};
	_ ->
	    add_postcomments(Cs, wrap(Node))
    end.

add_postcomments_1(Cs, #attr{com = none} = Attr) ->
    Attr#attr{com = #com{post = Cs}};
add_postcomments_1(Cs, #attr{com = Com} = Attr) ->
    Attr#attr{com = Com#com{post = Com#com.post ++ Cs}}.


%% =====================================================================
%% @doc Yields `false' if the node has no associated
%% comments, and `true' otherwise.
%%
%% Note: This is equivalent to `(get_precomments(Node) == [])
%% and (get_postcomments(Node) == [])', but potentially more
%% efficient.
%%
%% @see get_precomments/1
%% @see get_postcomments/1
%% @see remove_comments/1

-doc """
Yields `false` if the node has no associated comments, and `true` otherwise.

Note: This is equivalent to
`(get_precomments(Node) == []) and (get_postcomments(Node) == [])`, but
potentially more efficient.

_See also: _`get_postcomments/1`, `get_precomments/1`, `remove_comments/1`.
""".
-spec has_comments(syntaxTree()) -> boolean().

has_comments(#tree{attr = Attr}) ->
    case Attr#attr.com of
	none -> false;
	#com{pre = [], post = []} -> false;
	_ -> true
    end;
has_comments(#wrapper{attr = Attr}) ->
    case Attr#attr.com of
	none -> false;
	#com{pre = [], post = []} -> false;
	_ -> true
    end;
has_comments(_) -> false.


%% =====================================================================
%% @doc Clears the associated comments of `Node'.
%%
%% Note: This is equivalent to
%% `set_precomments(set_postcomments(Node, []), [])', but
%% potentially more efficient.
%%
%% @see set_precomments/2
%% @see set_postcomments/2

-doc """
Clears the associated comments of `Node`.

Note: This is equivalent to
[`set_precomments(set_postcomments(Node, []), [])`](`set_precomments/2`), but
potentially more efficient.

_See also: _`set_postcomments/2`, `set_precomments/2`.
""".
-spec remove_comments(syntaxTree()) -> syntaxTree().

remove_comments(Node) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = Attr#attr{com = none}};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = Attr#attr{com = none}};
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Copies the pre- and postcomments from `Source' to `Target'.
%%
%% Note: This is equivalent to
%% `set_postcomments(set_precomments(Target,
%% get_precomments(Source)), get_postcomments(Source))', but
%% potentially more efficient.
%%
%% @see comment/2
%% @see get_precomments/1
%% @see get_postcomments/1
%% @see set_precomments/2
%% @see set_postcomments/2

-doc """
Copies the pre- and postcomments from `Source` to `Target`.

Note: This is equivalent to
[`set_postcomments(set_precomments(Target, get_precomments(Source)), get_postcomments(Source))`](`set_postcomments/2`),
but potentially more efficient.

_See also: _`comment/2`, `get_postcomments/1`, `get_precomments/1`,
`set_postcomments/2`, `set_precomments/2`.
""".
-spec copy_comments(syntaxTree(), syntaxTree()) -> syntaxTree().

copy_comments(Source, Target) ->
    set_com(Target, get_com(Source)).


%% =====================================================================
%% @doc Appends the comments of `Source' to the current
%% comments of `Target'.
%%
%% Note: This is equivalent to
%% `add_postcomments(get_postcomments(Source),
%% add_precomments(get_precomments(Source), Target))', but
%% potentially more efficient.
%%
%% @see comment/2
%% @see get_precomments/1
%% @see get_postcomments/1
%% @see add_precomments/2
%% @see add_postcomments/2

-doc """
Appends the comments of `Source` to the current comments of `Target`.

Note: This is equivalent to
[`add_postcomments(get_postcomments(Source), add_precomments(get_precomments(Source), Target))`](`add_postcomments/2`),
but potentially more efficient.

_See also: _`add_postcomments/2`, `add_precomments/2`, `comment/2`,
`get_postcomments/1`, `get_precomments/1`.
""".
-spec join_comments(syntaxTree(), syntaxTree()) -> syntaxTree().

join_comments(Source, Target) ->
    add_postcomments(
      get_postcomments(Source),
      add_precomments(get_precomments(Source), Target)).


%% =====================================================================
%% @doc Returns the list of user annotations associated with a syntax
%% tree node. For a newly created node, this is the empty list. The
%% annotations may be any terms.
%%
%% @see set_ann/2
%% @see get_attrs/1

-doc """
Returns the list of user annotations associated with a syntax tree node. For a
newly created node, this is the empty list. The annotations may be any terms.

_See also: _`get_attrs/1`, `set_ann/2`.
""".
-spec get_ann(syntaxTree()) -> [term()].

get_ann(#tree{attr = Attr}) -> Attr#attr.ann;
get_ann(#wrapper{attr = Attr}) -> Attr#attr.ann;
get_ann(_) -> [].


%% =====================================================================
%% @doc Sets the list of user annotations of `Node' to `Annotations'.
%%
%% @see get_ann/1
%% @see add_ann/2
%% @see copy_ann/2

-doc """
Sets the list of user annotations of `Node` to `Annotations`.

_See also: _`add_ann/2`, `copy_ann/2`, `get_ann/1`.
""".
-spec set_ann(syntaxTree(), [term()]) -> syntaxTree().

set_ann(Node, As) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = Attr#attr{ann = As}};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = Attr#attr{ann = As}};
	_ ->
	    %% Assume we have an `erl_parse' node and create a wrapper
	    %% structure to carry the annotation.
	    set_ann(wrap(Node), As)
    end.


%% =====================================================================
%% @doc Appends the term `Annotation' to the list of user
%% annotations of `Node'.
%%
%% Note: this is equivalent to `set_ann(Node, [Annotation |
%% get_ann(Node)])', but potentially more efficient.
%%
%% @see get_ann/1
%% @see set_ann/2

-doc """
Appends the term `Annotation` to the list of user annotations of `Node`.

Note: this is equivalent to
[`set_ann(Node, [Annotation | get_ann(Node)])`](`set_ann/2`), but potentially
more efficient.

_See also: _`get_ann/1`, `set_ann/2`.
""".
-spec add_ann(term(), syntaxTree()) -> syntaxTree().

add_ann(A, Node) ->
    case Node of
	#tree{attr = Attr} ->
	    Node#tree{attr = Attr#attr{ann = [A | Attr#attr.ann]}};
	#wrapper{attr = Attr} ->
	    Node#wrapper{attr = Attr#attr{ann = [A | Attr#attr.ann]}};
	_ ->
	    %% Assume we have an `erl_parse' node and create a wrapper
	    %% structure to carry the annotation.
	    add_ann(A, wrap(Node))
    end.


%% =====================================================================
%% @doc Copies the list of user annotations from `Source' to `Target'.
%%
%% Note: this is equivalent to `set_ann(Target,
%% get_ann(Source))', but potentially more efficient.
%%
%% @see get_ann/1
%% @see set_ann/2

-doc """
Copies the list of user annotations from `Source` to `Target`.

Note: this is equivalent to [`set_ann(Target, get_ann(Source))`](`set_ann/2`),
but potentially more efficient.

_See also: _`get_ann/1`, `set_ann/2`.
""".
-spec copy_ann(syntaxTree(), syntaxTree()) -> syntaxTree().

copy_ann(Source, Target) ->
    set_ann(Target, get_ann(Source)).


%% =====================================================================
%% @doc Returns a representation of the attributes associated with a
%% syntax tree node. The attributes are all the extra information that
%% can be attached to a node. Currently, this includes position
%% information, source code comments, and user annotations. The result
%% of this function cannot be inspected directly; only attached to
%% another node (see {@link set_attrs/2}).
%%
%% For accessing individual attributes, see {@link get_pos/1},
%% {@link get_ann/1}, {@link get_precomments/1} and
%% {@link get_postcomments/1}.
%%
%% @type syntaxTreeAttributes(). This is an abstract representation of
%% syntax tree node attributes; see the function {@link get_attrs/1}.
%%
%% @see set_attrs/2
%% @see get_pos/1
%% @see get_ann/1
%% @see get_precomments/1
%% @see get_postcomments/1

-doc """
Returns a representation of the attributes associated with a syntax tree node.
The attributes are all the extra information that can be attached to a node.
Currently, this includes position information, source code comments, and user
annotations. The result of this function cannot be inspected directly; only
attached to another node (see `set_attrs/2`).

For accessing individual attributes, see `get_pos/1`, `get_ann/1`,
`get_precomments/1` and `get_postcomments/1`.

_See also: _`get_ann/1`, `get_pos/1`, `get_postcomments/1`, `get_precomments/1`,
`set_attrs/2`.
""".
-spec get_attrs(syntaxTree()) -> syntaxTreeAttributes().

get_attrs(#tree{attr = Attr}) -> Attr;
get_attrs(#wrapper{attr = Attr}) -> Attr;
get_attrs(Node) -> #attr{pos = get_pos(Node),
			 ann = get_ann(Node),
			 com = get_com(Node)}.


%% =====================================================================
%% @doc Sets the attributes of `Node' to `Attributes'.
%%
%% @see get_attrs/1
%% @see copy_attrs/2

-doc """
Sets the attributes of `Node` to `Attributes`.

_See also: _`copy_attrs/2`, `get_attrs/1`.
""".
-spec set_attrs(syntaxTree(), syntaxTreeAttributes()) -> syntaxTree().

set_attrs(Node, Attr) ->
    case Node of
	#tree{} ->
	    Node#tree{attr = Attr};
	#wrapper{} ->
	    Node#wrapper{attr = Attr};
	_ ->
	    set_attrs(wrap(Node), Attr)
    end.


%% =====================================================================
%% @doc Copies the attributes from `Source' to `Target'.
%%
%% Note: this is equivalent to `set_attrs(Target,
%% get_attrs(Source))', but potentially more efficient.
%%
%% @see get_attrs/1
%% @see set_attrs/2

-doc """
Copies the attributes from `Source` to `Target`.

Note: this is equivalent to
[`set_attrs(Target, get_attrs(Source))`](`set_attrs/2`), but potentially more
efficient.

_See also: _`get_attrs/1`, `set_attrs/2`.
""".
-spec copy_attrs(syntaxTree(), syntaxTree()) -> syntaxTree().

copy_attrs(S, T) ->
    set_attrs(T, get_attrs(S)).


%% =====================================================================
%% @equiv comment(none, Strings)

-doc "Equivalent to [comment(none, Strings)](`comment/2`).".
-spec comment([string()]) -> syntaxTree().

comment(Strings) ->
    comment(none, Strings).


%% =====================================================================
%% @doc Creates an abstract comment with the given padding and text. If
%% `Strings' is a (possibly empty) list
%% <code>["<em>Txt1</em>", ..., "<em>TxtN</em>"]</code>, the result
%% represents the source code text
%% <pre>
%%    %<em>Txt1</em>
%%    ...
%%    %<em>TxtN</em></pre>
%% `Padding' states the number of empty character positions
%% to the left of the comment separating it horizontally from
%% source code on the same line (if any). If `Padding' is
%% `none', a default positive number is used. If
%% `Padding' is an integer less than 1, there should be no
%% separating space. Comments are in themselves regarded as source
%% program forms.
%%
%% @see comment/1
%% @see is_form/1

-type padding() :: 'none' | integer().

-record(comment, {pad :: padding(), text :: [string()]}).

%% type(Node) = comment
%% data(Node) = #comment{pad :: Padding, text :: Strings}
%%
%%	Padding = none | integer()
%%	Strings = [string()]

-doc """
Creates an abstract comment with the given padding and text. If `Strings` is a
(possibly empty) list `["*Txt1*", ..., "*TxtN*"]`, the result represents the
source code text

```text
     %Txt1
     ...
     %TxtN
```

`Padding` states the number of empty character positions to the left of the
comment separating it horizontally from source code on the same line (if any).
If `Padding` is `none`, a default positive number is used. If `Padding` is an
integer less than 1, there should be no separating space. Comments are in
themselves regarded as source program forms.

_See also: _`comment/1`, `is_form/1`.
""".
-spec comment(padding(), [string()]) -> syntaxTree().

comment(Pad, Strings) ->
    tree(comment, #comment{pad = Pad, text = Strings}).


%% =====================================================================
%% @doc Returns the lines of text of the abstract comment.
%%
%% @see comment/2

-doc """
Returns the lines of text of the abstract comment.

_See also: _`comment/2`.
""".
-spec comment_text(syntaxTree()) -> [string()].

comment_text(Node) ->
    (data(Node))#comment.text.


%% =====================================================================
%% @doc Returns the amount of padding before the comment, or
%% `none'. The latter means that a default padding may be used.
%%
%% @see comment/2

-doc """
Returns the amount of padding before the comment, or `none`. The latter means
that a default padding may be used.

_See also: _`comment/2`.
""".
-spec comment_padding(syntaxTree()) -> padding().

comment_padding(Node) ->
    (data(Node))#comment.pad.


%% =====================================================================
%% @doc Creates an abstract sequence of "source code forms". If
%% `Forms' is `[F1, ..., Fn]', where each
%% `Fi' is a form (see {@link is_form/1}, the result
%% represents
%% <pre>
%%    <em>F1</em>
%%    ...
%%    <em>Fn</em></pre>
%% where the `Fi' are separated by one or more line breaks. A
%% node of type `form_list' is itself regarded as a source
%% code form; see {@link flatten_form_list/1}.
%%
%% Note: this is simply a way of grouping source code forms as a
%% single syntax tree, usually in order to form an Erlang module
%% definition.
%%
%% @see form_list_elements/1
%% @see is_form/1
%% @see flatten_form_list/1

%% type(Node) = form_list
%% data(Node) = [Form]
%%
%%	Form = syntaxTree()
%%	is_form(Form) = true

-doc """
Creates an abstract sequence of "source code forms". If `Forms` is
`[F1, ..., Fn]`, where each `Fi` is a form (see `is_form/1`, the result
represents

```text
F1
     ...
     Fn
```

where the `Fi` are separated by one or more line breaks. A node of type
`form_list` is itself regarded as a source code form; see `flatten_form_list/1`.

Note: this is simply a way of grouping source code forms as a single syntax
tree, usually in order to form an Erlang module definition.

_See also: _`flatten_form_list/1`, `form_list_elements/1`, `is_form/1`.
""".
-spec form_list([syntaxTree()]) -> syntaxTree().

form_list(Forms) ->
    tree(form_list, Forms).


%% =====================================================================
%% @doc Returns the list of subnodes of a `form_list' node.
%%
%% @see form_list/1

-doc """
Returns the list of subnodes of a `form_list` node.

_See also: _`form_list/1`.
""".
-spec form_list_elements(syntaxTree()) -> [syntaxTree()].

form_list_elements(Node) ->
    data(Node).


%% =====================================================================
%% @doc Flattens sublists of a `form_list' node. Returns
%% `Node' with all subtrees of type `form_list'
%% recursively expanded, yielding a single "flat" abstract form
%% sequence.
%%
%% @see form_list/1

-doc """
Flattens sublists of a `form_list` node. Returns `Node` with all subtrees of
type `form_list` recursively expanded, yielding a single "flat" abstract form
sequence.

_See also: _`form_list/1`.
""".
-spec flatten_form_list(syntaxTree()) -> syntaxTree().

flatten_form_list(Node) ->
    Fs = form_list_elements(Node),
    Fs1 = lists:reverse(flatten_form_list_1(Fs, [])),
    copy_attrs(Node, form_list(Fs1)).

flatten_form_list_1([F | Fs], As) ->
    case type(F) of
	form_list ->
	    As1 = flatten_form_list_1(form_list_elements(F), As),
	    flatten_form_list_1(Fs, As1);
	_ ->
	    flatten_form_list_1(Fs, [F | As])
    end;
flatten_form_list_1([], As) ->
    As.


%% =====================================================================
%% @doc Creates an abstract piece of source code text. The result
%% represents exactly the sequence of characters in `String'.
%% This is useful in cases when one wants full control of the resulting
%% output, e.g., for the appearance of floating-point numbers or macro
%% definitions.
%%
%% @see text_string/1

%% type(Node) = text
%% data(Node) = string()

-doc """
Creates an abstract piece of source code text. The result represents exactly the
sequence of characters in `String`. This is useful in cases when one wants full
control of the resulting output, e.g., for the appearance of floating-point
numbers or macro definitions.

_See also: _`text_string/1`.
""".
-spec text(string()) -> syntaxTree().

text(String) ->
    tree(text, String).


%% =====================================================================
%% @doc Returns the character sequence represented by a `text' node.
%%
%% @see text/1

-doc """
Returns the character sequence represented by a `text` node.

_See also: _`text/1`.
""".
-spec text_string(syntaxTree()) -> string().

text_string(Node) ->
    data(Node).


%% =====================================================================
%% @doc Creates an abstract variable with the given name.
%% `Name' may be any atom or string that represents a
%% lexically valid variable name, but <em>not</em> a single underscore
%% character; see {@link underscore/0}.
%%
%% Note: no checking is done whether the character sequence
%% represents a proper variable name, i.e., whether or not its first
%% character is an uppercase Erlang character, or whether it does not
%% contain control characters, whitespace, etc.
%%
%% @see variable_name/1
%% @see variable_literal/1
%% @see underscore/0

%% type(Node) = variable
%% data(Node) = atom()
%%
%% `erl_parse' representation:
%%
%% {var, Pos, Name}
%%
%%	Name = atom() \ '_'

-doc """
Creates an abstract variable with the given name. `Name` may be any atom or
string that represents a lexically valid variable name, but _not_ a single
underscore character; see `underscore/0`.

Note: no checking is done whether the character sequence represents a proper
variable name, i.e., whether or not its first character is an uppercase Erlang
character, or whether it does not contain control characters, whitespace, etc.

_See also: _`underscore/0`, `variable_literal/1`, `variable_name/1`.
""".
-spec variable(atom() | string()) -> syntaxTree().

variable(Name) when is_atom(Name) ->
    tree(variable, Name);
variable(Name) ->
    tree(variable, list_to_atom(Name)).

revert_variable(Node) ->
    Pos = get_pos(Node),
    Name = variable_name(Node),
    {var, Pos, Name}.


%% =====================================================================
%% @doc Returns the name of a `variable' node as an atom.
%%
%% @see variable/1

-doc """
Returns the name of a `variable` node as an atom.

_See also: _`variable/1`.
""".
-spec variable_name(syntaxTree()) -> atom().

variable_name(Node) ->
    case unwrap(Node) of
	{var, _, Name} ->
	    Name;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the name of a `variable' node as a string.
%%
%% @see variable/1

-doc """
Returns the name of a `variable` node as a string.

_See also: _`variable/1`.
""".
-spec variable_literal(syntaxTree()) -> string().

variable_literal(Node) ->
    case unwrap(Node) of
	{var, _, Name} ->
	    atom_to_list(Name);
	Node1 ->
	    atom_to_list(data(Node1))
    end.


%% =====================================================================
%% @doc Creates an abstract universal pattern ("`_'"). The
%% lexical representation is a single underscore character. Note that
%% this is <em>not</em> a variable, lexically speaking.
%%
%% @see variable/1

%% type(Node) = underscore
%% data(Node) = []
%%
%% `erl_parse' representation:
%%
%% {var, Pos, '_'}

-doc """
Creates an abstract universal pattern ("`_`"). The lexical representation is a
single underscore character. Note that this is _not_ a variable, lexically
speaking.

_See also: _`variable/1`.
""".
-spec underscore() -> syntaxTree().

underscore() ->
    tree(underscore, []).

revert_underscore(Node) ->
    Pos = get_pos(Node),
    {var, Pos, '_'}.


%% =====================================================================
%% @doc Creates an abstract integer literal. The lexical representation
%% is the canonical decimal numeral of `Value'.
%%
%% @see integer_value/1
%% @see integer_literal/1
%% @see is_integer/2

%% type(Node) = integer
%% data(Node) = integer()
%%
%% `erl_parse' representation:
%%
%% {integer, Pos, Value}
%%
%%	Value = integer()

-doc """
Creates an abstract integer literal. The lexical representation is the canonical
decimal numeral of `Value`.

_See also: _`integer_literal/1`, `integer_value/1`, `is_integer/2`.
""".
-spec integer(integer()) -> syntaxTree().

integer(Value) ->
    tree(integer, Value).

revert_integer(Node) ->
    Pos = get_pos(Node),
    {integer, Pos, integer_value(Node)}.


%% =====================================================================
%% @doc Returns `true' if `Node' has type
%% `integer' and represents `Value', otherwise `false'.
%%
%% @see integer/1

-doc """
Returns `true` if `Node` has type `integer` and represents `Value`, otherwise
`false`.

_See also: _`integer/1`.
""".
-spec is_integer(syntaxTree(), integer()) -> boolean().

is_integer(Node, Value) ->
    case unwrap(Node) of
	{integer, _, Value} ->
	    true;
	#tree{type = integer, data = Value} ->
	    true;
	_ ->
	    false
    end.


%% =====================================================================
%% @doc Returns the value represented by an `integer' node.
%%
%% @see integer/1

-doc """
Returns the value represented by an `integer` node.

_See also: _`integer/1`.
""".
-spec integer_value(syntaxTree()) -> integer().

integer_value(Node) ->
    case unwrap(Node) of
	{integer, _, Value} ->
	    Value;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the numeral string represented by an `integer' node.
%%
%% @see integer/1

-doc """
Returns the numeral string represented by an `integer` node.

_See also: _`integer/1`.
""".
-spec integer_literal(syntaxTree()) -> string().

integer_literal(Node) ->
    integer_to_list(integer_value(Node)).


%% =====================================================================
%% @doc Creates an abstract floating-point literal. The lexical
%% representation is the decimal floating-point numeral of `Value'.
%%
%% @see float_value/1
%% @see float_literal/1

%% type(Node) = float
%% data(Node) = Value
%%
%%	Value = float()
%%
%% `erl_parse' representation:
%%
%% {float, Pos, Value}
%%
%%	Value = float()

%% Note that under current versions of Erlang, the name `float/1' cannot
%% be used for local calls (i.e., within the module) - it will be
%% overridden by the type conversion BIF of the same name, so always use
%% `make_float/1' for local calls.

-doc """
Creates an abstract floating-point literal. The lexical representation is the
decimal floating-point numeral of `Value`.

_See also: _`float_literal/1`, `float_value/1`.
""".
-spec float(float()) -> syntaxTree().

float(Value) ->
    make_float(Value).

make_float(Value) ->
    tree(float, Value).

revert_float(Node) ->
    Pos = get_pos(Node),
    {float, Pos, float_value(Node)}.


%% =====================================================================
%% @doc Returns the value represented by a `float' node. Note
%% that floating-point values should usually not be compared for
%% equality.
%%
%% @see float/1

-doc """
Returns the value represented by a `float` node. Note that floating-point values
should usually not be compared for equality.

_See also: _`float/1`.
""".
-spec float_value(syntaxTree()) -> float().

float_value(Node) ->
    case unwrap(Node) of
	{float, _, Value} ->
	    Value;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the numeral string represented by a `float' node.
%%
%% @see float/1

-doc """
Returns the numeral string represented by a `float` node.

_See also: _`float/1`.
""".
-spec float_literal(syntaxTree()) -> string().

float_literal(Node) ->
    float_to_list(float_value(Node)).


%% =====================================================================
%% @doc Creates an abstract character literal. The result represents
%% "<code>$<em>Name</em></code>", where `Name' corresponds to
%% `Value'.
%%
%% Note: the literal corresponding to a particular character value is
%% not uniquely defined. E.g., the character "`a'" can be
%% written both as "`$a'" and "`$\141'", and a Tab
%% character can be written as "`$\11'", "`$\011'"
%% or "`$\t'".
%%
%% @see char_value/1
%% @see char_literal/1
%% @see char_literal/2
%% @see is_char/2

%% type(Node) = char
%% data(Node) = char()
%%
%% `erl_parse' representation:
%%
%% {char, Pos, Code}
%%
%%	Code = integer()

-doc """
Creates an abstract character literal. The result represents "`$*Name*`", where
`Name` corresponds to `Value`.

Note: the literal corresponding to a particular character value is not uniquely
defined. E.g., the character "`a`" can be written both as "`$a`" and "`$\141`",
and a Tab character can be written as "`$\11`", "`$\011`" or "`$\t`".

_See also: _`char_literal/1`, `char_literal/2`, `char_value/1`, `is_char/2`.
""".
-spec char(char()) -> syntaxTree().

char(Char) ->
    tree(char, Char).

revert_char(Node) ->
    Pos = get_pos(Node),
    {char, Pos, char_value(Node)}.


%% =====================================================================
%% @doc Returns `true' if `Node' has type
%% `char' and represents `Value', otherwise `false'.
%%
%% @see char/1

-doc """
Returns `true` if `Node` has type `char` and represents `Value`, otherwise
`false`.

_See also: _`char/1`.
""".
-spec is_char(syntaxTree(), char()) -> boolean().

is_char(Node, Value) ->
    case unwrap(Node) of
	{char, _, Value} ->
	    true;
	#tree{type = char, data = Value} ->
	    true;
	_ ->
	    false
    end.


%% =====================================================================
%% @doc Returns the value represented by a `char' node.
%%
%% @see char/1

-doc """
Returns the value represented by a `char` node.

_See also: _`char/1`.
""".
-spec char_value(syntaxTree()) -> char().

char_value(Node) ->
    case unwrap(Node) of
	{char, _, Char} ->
	    Char;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the literal string represented by a `char'
%% node. This includes the leading "`$'" character.
%% Characters beyond 255 will be escaped.
%%
%% @see char/1

-doc """
Returns the literal string represented by a `char` node. This includes the
leading "`$`" character. Characters beyond 255 will be escaped.

_See also: _`char/1`.
""".
-spec char_literal(syntaxTree()) -> nonempty_string().

char_literal(Node) ->
    char_literal(Node, latin1).


%% =====================================================================
%% @doc Returns the literal string represented by a `char'
%% node. This includes the leading "`$'" character.
%% Depending on the encoding a character beyond 255 will be escaped
%% (`latin1') or copied as is (`utf8').
%%
%% @see char/1

-type encoding() :: 'utf8' | 'unicode' | 'latin1'.

-doc """
Returns the literal string represented by a `char` node. This includes the
leading "`$`" character. Depending on the encoding a character beyond 255 will
be escaped (`latin1`) or copied as is (`utf8`).

_See also: _`char/1`.
""".
-spec char_literal(syntaxTree(), encoding()) -> nonempty_string().

char_literal(Node, unicode) ->
    io_lib:write_char(char_value(Node));
char_literal(Node, utf8) ->
    io_lib:write_char(char_value(Node));
char_literal(Node, latin1) ->
    io_lib:write_char_as_latin1(char_value(Node)).


%% =====================================================================
%% @doc Creates an abstract string literal. The result represents
%% <code>"<em>Text</em>"</code> (including the surrounding
%% double-quotes), where `Text' corresponds to the sequence
%% of characters in `Value', but not representing a
%% <em>specific</em> string literal.
%%
%% For example, the result of `string("x\ny")' represents any and all of
%% `"x\ny"', `"x\12y"', `"x\012y"' and `"x\^Jy"'; see {@link char/1}.
%%
%% @see string_value/1
%% @see string_literal/1
%% @see string_literal/2
%% @see is_string/2
%% @see char/1

%% type(Node) = string
%% data(Node) = string()
%%
%% `erl_parse' representation:
%%
%% {string, Pos, Chars}
%%
%%	Chars = string()

-doc """
Creates an abstract string literal. The result represents `"*Text*"` (including
the surrounding double-quotes), where `Text` corresponds to the sequence of
characters in `Value`, but not representing a _specific_ string literal.

For example, the result of [`string("x\ny")`](`string/1`) represents any and all
of `"x\ny"`, `"x\12y"`, `"x\012y"` and `"x\^Jy"`; see `char/1`.

_See also: _`char/1`, `is_string/2`, `string_literal/1`, `string_literal/2`,
`string_value/1`.
""".
-spec string(string()) -> syntaxTree().

string(String) ->
    tree(string, String).

revert_string(Node) ->
    Pos = get_pos(Node),
    {string, Pos, string_value(Node)}.


%% =====================================================================
%% @doc Returns `true' if `Node' has type
%% `string' and represents `Value', otherwise `false'.
%%
%% @see string/1

-doc """
Returns `true` if `Node` has type `string` and represents `Value`, otherwise
`false`.

_See also: _`string/1`.
""".
-spec is_string(syntaxTree(), string()) -> boolean().

is_string(Node, Value) ->
    case unwrap(Node) of
	{string, _, Value} ->
	    true;
	#tree{type = string, data = Value} ->
	    true;
	_ ->
	    false
    end.


%% =====================================================================
%% @doc Returns the value represented by a `string' node.
%%
%% @see string/1

-doc """
Returns the value represented by a `string` node.

_See also: _`string/1`.
""".
-spec string_value(syntaxTree()) -> string().

string_value(Node) ->
    case unwrap(Node) of
	{string, _, List} ->
	    List;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the literal string represented by a `string'
%% node. This includes surrounding double-quote characters.
%% Characters beyond 255 will be escaped.
%%
%% @see string/1

-doc """
Returns the literal string represented by a `string` node. This includes
surrounding double-quote characters. Characters beyond 255 will be escaped.

_See also: _`string/1`.
""".
-spec string_literal(syntaxTree()) -> nonempty_string().

string_literal(Node) ->
    string_literal(Node, latin1).


%% =====================================================================
%% @doc Returns the literal string represented by a `string'
%% node. This includes surrounding double-quote characters.
%% Depending on the encoding characters beyond 255 will be escaped
%% (`latin1') or copied as is (`utf8').
%%
%% @see string/1

-doc """
Returns the literal string represented by a `string` node. This includes
surrounding double-quote characters. Depending on the encoding characters beyond
255 will be escaped (`latin1`) or copied as is (`utf8`).

_See also: _`string/1`.
""".
-spec string_literal(syntaxTree(), encoding()) -> nonempty_string().

string_literal(Node, utf8) ->
    io_lib:write_string(string_value(Node));
string_literal(Node, unicode) ->
    io_lib:write_string(string_value(Node));
string_literal(Node, latin1) ->
    io_lib:write_string_as_latin1(string_value(Node)).


%% =====================================================================
%% @doc Creates an abstract atom literal. The print name of the atom is
%% the character sequence represented by `Name'.
%%
%% @see atom_value/1
%% @see atom_name/1
%% @see atom_literal/1
%% @see atom_literal/2
%% @see is_atom/2

%% type(Node) = atom
%% data(Node) = atom()
%%
%% `erl_parse' representation:
%%
%% {atom, Pos, Value}
%%
%%	Value = atom()

-doc """
Creates an abstract atom literal. The print name of the atom is the character
sequence represented by `Name`.

_See also: _`atom_literal/1`, `atom_literal/2`, `atom_name/1`, `atom_value/1`,
`is_atom/2`.
""".
-spec atom(atom() | string()) -> syntaxTree().

atom(Name) when is_atom(Name) ->
    tree(atom, Name);
atom(Name) ->
    tree(atom, list_to_atom(Name)).

revert_atom(Node) ->
    Pos = get_pos(Node),
    {atom, Pos, atom_value(Node)}.


%% =====================================================================
%% @doc Returns `true' if `Node' has type
%% `atom' and represents `Value', otherwise `false'.
%%
%% @see atom/1

-doc """
Returns `true` if `Node` has type `atom` and represents `Value`, otherwise
`false`.

_See also: _`atom/1`.
""".
-spec is_atom(syntaxTree(), atom()) -> boolean().

is_atom(Node, Value) ->
    case unwrap(Node) of
	{atom, _, Value} ->
	    true;
	#tree{type = atom, data = Value} ->
	    true;
	_ ->
	    false
    end.


%% =====================================================================
%% @doc Returns the value represented by an `atom' node.
%%
%% @see atom/1

-doc """
Returns the value represented by an `atom` node.

_See also: _`atom/1`.
""".
-spec atom_value(syntaxTree()) -> atom().

atom_value(Node) ->
    case unwrap(Node) of
	{atom, _, Name} ->
	    Name;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the printname of an `atom' node.
%%
%% @see atom/1

-doc """
Returns the printname of an `atom` node.

_See also: _`atom/1`.
""".
-spec atom_name(syntaxTree()) -> string().

atom_name(Node) ->
    atom_to_list(atom_value(Node)).


%% =====================================================================
%% @doc Returns the literal string represented by an `atom'
%% node. This includes surrounding single-quote characters if necessary.
%% Characters beyond 255 will be escaped.
%%
%% Note that e.g. the result of `atom("x\ny")' represents
%% any and all of `'x\ny'', `'x\12y'',
%% `'x\012y'' and `'x\^Jy\''; see {@link string/1}.
%%
%% @see atom/1
%% @see string/1

-doc """
Returns the literal string represented by an `atom` node. This includes
surrounding single-quote characters if necessary. Characters beyond 255 will be
escaped.

Note that e.g. the result of [`atom("x\ny")`](`atom/1`) represents any and all
of \`x\\ny'', \`x\\12y'', \`x\\012y'' and \`x\\^Jy\\''; see `string/1`.

_See also: _`atom/1`, `string/1`.
""".
-spec atom_literal(syntaxTree()) -> string().

atom_literal(Node) ->
    atom_literal(Node, latin1).

%% =====================================================================
%% @doc Returns the literal string represented by an `atom'
%% node. This includes surrounding single-quote characters if necessary.
%% Depending on the encoding a character beyond 255 will be escaped
%% (`latin1') or copied as is (`utf8').
%%
%% @see atom/1
%% @see atom_literal/1
%% @see string/1

-doc """
Returns the literal string represented by an `atom` node. This includes
surrounding single-quote characters if necessary. Depending on the encoding a
character beyond 255 will be escaped (`latin1`) or copied as is (`utf8`).

_See also: _`atom/1`, `atom_literal/1`, `string/1`.
""".
-spec atom_literal(syntaxTree(), utf8 | unicode | latin1) -> string().

atom_literal(Node, utf8) ->
    io_lib:write_atom(atom_value(Node));
atom_literal(Node, unicode) ->
    io_lib:write_atom(atom_value(Node));
atom_literal(Node, latin1) ->
    io_lib:write_atom_as_latin1(atom_value(Node)).

%% =====================================================================
%% @equiv map_expr(none, Fields)

-doc "Equivalent to [map_expr(none, Fields)](`map_expr/2`).".
-spec map_expr([syntaxTree()]) -> syntaxTree().

map_expr(Fields) ->
    map_expr(none, Fields).


%% =====================================================================
%% @doc Creates an abstract map expression. If `Fields' is
%% `[F1, ..., Fn]', then if `Argument' is `none', the result represents
%% "<code>#{<em>F1</em>, ..., <em>Fn</em>}</code>",
%% otherwise it represents
%% "<code><em>Argument</em>#{<em>F1</em>, ..., <em>Fn</em>}</code>".
%%
%% @see map_expr/1
%% @see map_expr_argument/1
%% @see map_expr_fields/1
%% @see map_field_assoc/2
%% @see map_field_exact/2

-record(map_expr, {argument :: 'none' | syntaxTree(),
                   fields   :: [syntaxTree()]}).

%% `erl_parse' representation:
%%
%% {map, Pos, Fields}
%% {map, Pos, Argument, Fields}

-doc """
Creates an abstract map expression. If `Fields` is `[F1, ..., Fn]`, then if
`Argument` is `none`, the result represents "`#{*F1*, ..., *Fn*}`", otherwise it
represents "`*Argument*#{*F1*, ..., *Fn*}`".

_See also: _`map_expr/1`, `map_expr_argument/1`, `map_expr_fields/1`,
`map_field_assoc/2`, `map_field_exact/2`.
""".
-spec map_expr('none' | syntaxTree(), [syntaxTree()]) -> syntaxTree().

map_expr(Argument, Fields) ->
    tree(map_expr, #map_expr{argument = Argument, fields = Fields}).

revert_map_expr(Node) ->
    Pos = get_pos(Node),
    Argument = map_expr_argument(Node),
    Fields = map_expr_fields(Node),
    case Argument of
        none ->
            {map, Pos, Fields};
        _ ->
            {map, Pos, Argument, Fields}
    end.


%% =====================================================================
%% @doc Returns the argument subtree of a `map_expr' node, if any. If `Node'
%% represents "<code>#{...}</code>", `none' is returned.
%% Otherwise, if `Node' represents "<code><em>Argument</em>#{...}</code>",
%% `Argument' is returned.
%%
%% @see map_expr/2

-doc """
Returns the argument subtree of a `map_expr` node, if any. If `Node` represents
"`#{...}`", `none` is returned. Otherwise, if `Node` represents
"`*Argument*#{...}`", `Argument` is returned.

_See also: _`map_expr/2`.
""".
-spec map_expr_argument(syntaxTree()) -> 'none' | syntaxTree().

map_expr_argument(Node) ->
    case unwrap(Node) of
        {map, _, _} ->
            none;
        {map, _, Argument, _} ->
            Argument;
        Node1 ->
            (data(Node1))#map_expr.argument
    end.


%% =====================================================================
%% @doc Returns the list of field subtrees of a `map_expr' node.
%%
%% @see map_expr/2

-doc """
Returns the list of field subtrees of a `map_expr` node.

_See also: _`map_expr/2`.
""".
-spec map_expr_fields(syntaxTree()) -> [syntaxTree()].

map_expr_fields(Node) ->
    case unwrap(Node) of
        {map, _, Fields} ->
            Fields;
        {map, _, _, Fields} ->
            Fields;
        Node1 ->
            (data(Node1))#map_expr.fields
    end.


%% =====================================================================
%% @doc Creates an abstract map assoc field. The result represents
%% "<code><em>Name</em> => <em>Value</em></code>".
%%
%% @see map_field_assoc_name/1
%% @see map_field_assoc_value/1
%% @see map_expr/2

-record(map_field_assoc, {name :: syntaxTree(), value :: syntaxTree()}).

%% `erl_parse' representation:
%%
%% {map_field_assoc, Pos, Name, Value}

-doc """
Creates an abstract map assoc field. The result represents
"`*Name* => *Value*`".

_See also: _`map_expr/2`, `map_field_assoc_name/1`, `map_field_assoc_value/1`.
""".
-spec map_field_assoc(syntaxTree(), syntaxTree()) -> syntaxTree().

map_field_assoc(Name, Value) ->
    tree(map_field_assoc, #map_field_assoc{name = Name, value = Value}).

revert_map_field_assoc(Node) ->
    Pos = get_pos(Node),
    Name = map_field_assoc_name(Node),
    Value = map_field_assoc_value(Node),
    {map_field_assoc, Pos, Name, Value}.


%% =====================================================================
%% @doc Returns the name subtree of a `map_field_assoc' node.
%%
%% @see map_field_assoc/2

-doc """
Returns the name subtree of a `map_field_assoc` node.

_See also: _`map_field_assoc/2`.
""".
-spec map_field_assoc_name(syntaxTree()) -> syntaxTree().

map_field_assoc_name(Node) ->
    case unwrap(Node) of
        {map_field_assoc, _, Name, _} ->
            Name;
        Node1 ->
            (data(Node1))#map_field_assoc.name
    end.


%% =====================================================================
%% @doc Returns the value subtree of a `map_field_assoc' node.
%%
%% @see map_field_assoc/2

-doc """
Returns the value subtree of a `map_field_assoc` node.

_See also: _`map_field_assoc/2`.
""".
-spec map_field_assoc_value(syntaxTree()) -> syntaxTree().

map_field_assoc_value(Node) ->
    case unwrap(Node) of
        {map_field_assoc, _, _, Value} ->
            Value;
        Node1 ->
            (data(Node1))#map_field_assoc.value
    end.


%% =====================================================================
%% @doc Creates an abstract map exact field. The result represents
%% "<code><em>Name</em> := <em>Value</em></code>".
%%
%% @see map_field_exact_name/1
%% @see map_field_exact_value/1
%% @see map_expr/2

-record(map_field_exact, {name :: syntaxTree(), value :: syntaxTree()}).

%% `erl_parse' representation:
%%
%% {map_field_exact, Pos, Name, Value}

-doc """
Creates an abstract map exact field. The result represents
"`*Name* := *Value*`".

_See also: _`map_expr/2`, `map_field_exact_name/1`, `map_field_exact_value/1`.
""".
-spec map_field_exact(syntaxTree(), syntaxTree()) -> syntaxTree().

map_field_exact(Name, Value) ->
    tree(map_field_exact, #map_field_exact{name = Name, value = Value}).

revert_map_field_exact(Node) ->
    Pos = get_pos(Node),
    Name = map_field_exact_name(Node),
    Value = map_field_exact_value(Node),
    {map_field_exact, Pos, Name, Value}.


%% =====================================================================
%% @doc Returns the name subtree of a `map_field_exact' node.
%%
%% @see map_field_exact/2

-doc """
Returns the name subtree of a `map_field_exact` node.

_See also: _`map_field_exact/2`.
""".
-spec map_field_exact_name(syntaxTree()) -> syntaxTree().

map_field_exact_name(Node) ->
    case unwrap(Node) of
        {map_field_exact, _, Name, _} ->
            Name;
        Node1 ->
            (data(Node1))#map_field_exact.name
    end.


%% =====================================================================
%% @doc Returns the value subtree of a `map_field_exact' node.
%%
%% @see map_field_exact/2

-doc """
Returns the value subtree of a `map_field_exact` node.

_See also: _`map_field_exact/2`.
""".
-spec map_field_exact_value(syntaxTree()) -> syntaxTree().

map_field_exact_value(Node) ->
    case unwrap(Node) of
        {map_field_exact, _, _, Value} ->
            Value;
        Node1 ->
            (data(Node1))#map_field_exact.value
    end.


%% =====================================================================
%% @doc Creates an abstract tuple. If `Elements' is
%% `[X1, ..., Xn]', the result represents
%% "<code>{<em>X1</em>, ..., <em>Xn</em>}</code>".
%%
%% Note: The Erlang language has distinct 1-tuples, i.e.,
%% `{X}' is always distinct from `X' itself.
%%
%% @see tuple_elements/1
%% @see tuple_size/1

%% type(Node) = tuple
%% data(Node) = Elements
%%
%%	Elements = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {tuple, Pos, Elements}
%%
%%	Elements = [erl_parse()]

-doc """
Creates an abstract tuple. If `Elements` is `[X1, ..., Xn]`, the result
represents "`{*X1*, ..., *Xn*}`".

Note: The Erlang language has distinct 1-tuples, i.e., `{X}` is always distinct
from `X` itself.

_See also: _`tuple_elements/1`, `tuple_size/1`.
""".
-spec tuple([syntaxTree()]) -> syntaxTree().

tuple(List) ->
    tree(tuple, List).

revert_tuple(Node) ->
    Pos = get_pos(Node),
    {tuple, Pos, tuple_elements(Node)}.


%% =====================================================================
%% @doc Returns the list of element subtrees of a `tuple' node.
%%
%% @see tuple/1

-doc """
Returns the list of element subtrees of a `tuple` node.

_See also: _`tuple/1`.
""".
-spec tuple_elements(syntaxTree()) -> [syntaxTree()].

tuple_elements(Node) ->
    case unwrap(Node) of
	{tuple, _, List} ->
	    List;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the number of elements of a `tuple' node.
%%
%% Note: this is equivalent to
%% `length(tuple_elements(Node))', but potentially more
%% efficient.
%%
%% @see tuple/1
%% @see tuple_elements/1

-doc """
Returns the number of elements of a `tuple` node.

Note: this is equivalent to [`length(tuple_elements(Node))`](`length/1`), but
potentially more efficient.

_See also: _`tuple/1`, `tuple_elements/1`.
""".
-spec tuple_size(syntaxTree()) -> non_neg_integer().

tuple_size(Node) ->
    length(tuple_elements(Node)).


%% =====================================================================
%% @equiv list(List, none)

-doc "Equivalent to [list(List, none)](`list/2`).".
-spec list([syntaxTree()]) -> syntaxTree().

list(List) ->
    list(List, none).


%% =====================================================================
%% @doc Constructs an abstract list skeleton. The result has type
%% `list' or `nil'. If `List' is a
%% nonempty list `[E1, ..., En]', the result has type
%% `list' and represents either "<code>[<em>E1</em>, ...,
%% <em>En</em>]</code>", if `Tail' is `none', or
%% otherwise "<code>[<em>E1</em>, ..., <em>En</em> |
%% <em>Tail</em>]</code>". If `List' is the empty list,
%% `Tail' <em>must</em> be `none', and in that
%% case the result has type `nil' and represents
%% "`[]'" (see {@link nil/0}).
%%
%% The difference between lists as semantic objects (built up of
%% individual "cons" and "nil" terms) and the various syntactic forms
%% for denoting lists may be bewildering at first. This module provides
%% functions both for exact control of the syntactic representation as
%% well as for the simple composition and deconstruction in terms of
%% cons and head/tail operations.
%%
%% Note: in `list(Elements, none)', the "nil" list
%% terminator is implicit and has no associated information (see
%% {@link get_attrs/1}), while in the seemingly equivalent
%% `list(Elements, Tail)' when `Tail' has type
%% `nil', the list terminator subtree `Tail' may
%% have attached attributes such as position, comments, and annotations,
%% which will be preserved in the result.
%%
%% @see nil/0
%% @see list/1
%% @see list_prefix/1
%% @see list_suffix/1
%% @see cons/2
%% @see list_head/1
%% @see list_tail/1
%% @see is_list_skeleton/1
%% @see is_proper_list/1
%% @see list_elements/1
%% @see list_length/1
%% @see normalize_list/1
%% @see compact_list/1
%% @see get_attrs/1

-record(list, {prefix :: [syntaxTree()], suffix :: 'none' | syntaxTree()}).

%% type(Node) = list
%% data(Node) = #list{prefix :: Elements, suffix :: Tail}
%%
%%	    Elements = [syntaxTree()]
%%	    Tail = none | syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {cons, Pos, Head, Tail}
%%
%%	Head = Tail = [erl_parse()]
%%
%%	This represents `[<Head> | <Tail>]', or more generally `[<Head>
%%	<Suffix>]' where the form of <Suffix> can depend on the
%%	structure of <Tail>; there is no fixed printed form.

-doc """
Constructs an abstract list skeleton. The result has type `list` or `nil`. If
`List` is a nonempty list `[E1, ..., En]`, the result has type `list` and
represents either "`[*E1*, ..., *En*]`", if `Tail` is `none`, or otherwise
"`[*E1*, ..., *En* | *Tail*]`". If `List` is the empty list, `Tail`_must_ be
`none`, and in that case the result has type `nil` and represents "`[]`" (see
`nil/0`).

The difference between lists as semantic objects (built up of individual "cons"
and "nil" terms) and the various syntactic forms for denoting lists may be
bewildering at first. This module provides functions both for exact control of
the syntactic representation as well as for the simple composition and
deconstruction in terms of cons and head/tail operations.

Note: in [`list(Elements, none)`](`list/2`), the "nil" list terminator is
implicit and has no associated information (see `get_attrs/1`), while in the
seemingly equivalent [`list(Elements, Tail)`](`list/2`) when `Tail` has type
`nil`, the list terminator subtree `Tail` may have attached attributes such as
position, comments, and annotations, which will be preserved in the result.

_See also: _`compact_list/1`, `cons/2`, `get_attrs/1`, `is_list_skeleton/1`,
`is_proper_list/1`, `list/1`, `list_elements/1`, `list_head/1`, `list_length/1`,
`list_prefix/1`, `list_suffix/1`, `list_tail/1`, `nil/0`, `normalize_list/1`.
""".
-spec list([syntaxTree()], 'none' | syntaxTree()) -> syntaxTree().

list([], none) ->
    nil();
list(Elements, Tail) when Elements =/= [] ->
    tree(list, #list{prefix = Elements, suffix = Tail}).

revert_list(Node) ->
    Pos = get_pos(Node),
    Prefix = list_prefix(Node),
    Suffix = case list_suffix(Node) of
	    none ->
            LastPos = get_pos(lists:last(Prefix)),
            LastLocation = case erl_anno:end_location(LastPos) of
                undefined -> erl_anno:location(LastPos);
                Location -> Location
            end,
            revert_nil(set_pos(nil(), erl_anno:set_location(LastLocation, Pos)));
	    Suffix1 ->
            Suffix1
	end,
    lists:foldr(fun (Head, Tail) ->
        HeadPos = get_pos(Head),
        HeadLocation = erl_anno:location(HeadPos),
        {cons, erl_anno:set_location(HeadLocation, Pos), Head, Tail}
    end, Suffix, Prefix).

%% =====================================================================
%% @doc Creates an abstract empty list. The result represents
%% "`[]'". The empty list is traditionally called "nil".
%%
%% @see list/2
%% @see is_list_skeleton/1

%% type(Node) = nil
%% data(Node) = term()
%%
%% `erl_parse' representation:
%%
%% {nil, Pos}

-doc """
Creates an abstract empty list. The result represents "`[]`". The empty list is
traditionally called "nil".

_See also: _`is_list_skeleton/1`, `list/2`.
""".
-spec nil() -> syntaxTree().

nil() ->
    tree(nil).

revert_nil(Node) ->
    Pos = get_pos(Node),
    {nil, Pos}.


%% =====================================================================
%% @doc Returns the prefix element subtrees of a `list' node.
%% If `Node' represents "<code>[<em>E1</em>, ...,
%% <em>En</em>]</code>" or "<code>[<em>E1</em>, ..., <em>En</em> |
%% <em>Tail</em>]</code>", the returned value is `[E1, ...,
%% En]'.
%%
%% @see list/2

-doc """
Returns the prefix element subtrees of a `list` node. If `Node` represents
"`[*E1*, ..., *En*]`" or "`[*E1*, ..., *En* | *Tail*]`", the returned value is
`[E1, ..., En]`.

_See also: _`list/2`.
""".
-spec list_prefix(syntaxTree()) -> [syntaxTree()].

list_prefix(Node) ->
    case unwrap(Node) of
	{cons, _, Head, Tail} ->
	    [Head | cons_prefix(Tail)];
	Node1 ->
	    (data(Node1))#list.prefix
    end.

%% collects sequences of conses; cf. cons_suffix/1 below
cons_prefix({cons, _, Head, Tail}) ->
    [Head | cons_prefix(Tail)];
cons_prefix(_) ->
    [].


%% =====================================================================
%% @doc Returns the suffix subtree of a `list' node, if one
%% exists. If `Node' represents "<code>[<em>E1</em>, ...,
%% <em>En</em> | <em>Tail</em>]</code>", the returned value is
%% `Tail', otherwise, i.e., if `Node' represents
%% "<code>[<em>E1</em>, ..., <em>En</em>]</code>", `none' is
%% returned.
%%
%% Note that even if this function returns some `Tail'
%% that is not `none', the type of `Tail' can be
%% `nil', if the tail has been given explicitly, and the list
%% skeleton has not been compacted (see {@link compact_list/1}).
%%
%% @see list/2
%% @see nil/0
%% @see compact_list/1

-doc """
Returns the suffix subtree of a `list` node, if one exists. If `Node` represents
"`[*E1*, ..., *En* | *Tail*]`", the returned value is `Tail`, otherwise, i.e.,
if `Node` represents "`[*E1*, ..., *En*]`", `none` is returned.

Note that even if this function returns some `Tail` that is not `none`, the type
of `Tail` can be `nil`, if the tail has been given explicitly, and the list
skeleton has not been compacted (see `compact_list/1`).

_See also: _`compact_list/1`, `list/2`, `nil/0`.
""".
-spec list_suffix(syntaxTree()) -> 'none' | syntaxTree().

list_suffix(Node) ->
    case unwrap(Node) of
	{cons, _, _, Tail} ->
	    case cons_suffix(Tail) of
		{nil, _} ->
		    none;
		Tail1 ->
		    Tail1
	    end;
	Node1 ->
	    (data(Node1))#list.suffix
    end.

%% skips sequences of conses; cf. cons_prefix/1 above
cons_suffix({cons, _, _, Tail}) ->
    cons_suffix(Tail);
cons_suffix(Tail) ->
    Tail.


%% =====================================================================
%% @doc "Optimising" list skeleton cons operation. Creates an abstract
%% list skeleton whose first element is `Head' and whose tail
%% corresponds to `Tail'. This is similar to
%% `list([Head], Tail)', except that `Tail' may
%% not be `none', and that the result does not necessarily
%% represent exactly "<code>[<em>Head</em> | <em>Tail</em>]</code>", but
%% may depend on the `Tail' subtree. E.g., if
%% `Tail' represents `[X, Y]', the result may
%% represent "<code>[<em>Head</em>, X, Y]</code>", rather than
%% "<code>[<em>Head</em> | [X, Y]]</code>". Annotations on
%% `Tail' itself may be lost if `Tail' represents
%% a list skeleton, but comments on `Tail' are propagated to
%% the result.
%%
%% @see list/2
%% @see list_head/1
%% @see list_tail/1

-doc """
"Optimising" list skeleton cons operation. Creates an abstract list skeleton
whose first element is `Head` and whose tail corresponds to `Tail`. This is
similar to [`list([Head], Tail)`](`list/2`), except that `Tail` may not be
`none`, and that the result does not necessarily represent exactly
"`[*Head* | *Tail*]`", but may depend on the `Tail` subtree. E.g., if `Tail`
represents `[X, Y]`, the result may represent "`[*Head*, X, Y]`", rather than
"`[*Head* | [X, Y]]`". Annotations on `Tail` itself may be lost if `Tail`
represents a list skeleton, but comments on `Tail` are propagated to the result.

_See also: _`list/2`, `list_head/1`, `list_tail/1`.
""".
-spec cons(syntaxTree(), syntaxTree()) -> syntaxTree().

cons(Head, Tail) ->
    case type(Tail) of
	list ->
	    copy_comments(Tail, list([Head | list_prefix(Tail)],
				     list_suffix(Tail)));
	nil ->
	    copy_comments(Tail, list([Head]));
	_ ->
	    list([Head], Tail)
    end.


%% =====================================================================
%% @doc Returns the head element subtree of a `list' node. If
%% `Node' represents "<code>[<em>Head</em> ...]</code>", the
%% result will represent "<code><em>Head</em></code>".
%%
%% @see list/2
%% @see list_tail/1
%% @see cons/2

-doc """
Returns the head element subtree of a `list` node. If `Node` represents
"`[*Head* ...]`", the result will represent "`*Head*`".

_See also: _`cons/2`, `list/2`, `list_tail/1`.
""".
-spec list_head(syntaxTree()) -> syntaxTree().

list_head(Node) ->
    hd(list_prefix(Node)).


%% =====================================================================
%% @doc Returns the tail of a `list' node. If
%% `Node' represents a single-element list
%% "<code>[<em>E</em>]</code>", then the result has type
%% `nil', representing "`[]'". If
%% `Node' represents "<code>[<em>E1</em>, <em>E2</em>
%% ...]</code>", the result will represent "<code>[<em>E2</em>
%% ...]</code>", and if `Node' represents
%% "<code>[<em>Head</em> | <em>Tail</em>]</code>", the result will
%% represent "<code><em>Tail</em></code>".
%%
%% @see list/2
%% @see list_head/1
%% @see cons/2

-doc """
Returns the tail of a `list` node. If `Node` represents a single-element list
"`[*E*]`", then the result has type `nil`, representing "`[]`". If `Node`
represents "`[*E1*, *E2* ...]`", the result will represent "`[*E2* ...]`", and
if `Node` represents "`[*Head* | *Tail*]`", the result will represent
"`*Tail*`".

_See also: _`cons/2`, `list/2`, `list_head/1`.
""".
-spec list_tail(syntaxTree()) -> syntaxTree().

list_tail(Node) ->
    Tail = list_suffix(Node),
    case tl(list_prefix(Node)) of
	[] ->
	    if Tail =:= none ->
		    nil();    % implicit list terminator.
	       true ->
		    Tail
	    end;
	Es ->
	    list(Es, Tail)    % `Es' is nonempty.
    end.


%% =====================================================================
%% @doc Returns `true' if `Node' has type
%% `list' or `nil', otherwise `false'.
%%
%% @see list/2
%% @see nil/0

-doc """
Returns `true` if `Node` has type `list` or `nil`, otherwise `false`.

_See also: _`list/2`, `nil/0`.
""".
-spec is_list_skeleton(syntaxTree()) -> boolean().

is_list_skeleton(Node) ->
    case type(Node) of
	list -> true;
	nil -> true;
	_ -> false
    end.


%% =====================================================================
%% @doc Returns `true' if `Node' represents a
%% proper list, and `false' otherwise. A proper list is a
%% list skeleton either on the form "`[]'" or
%% "<code>[<em>E1</em>, ..., <em>En</em>]</code>", or "<code>[... |
%% <em>Tail</em>]</code>" where recursively `Tail' also
%% represents a proper list.
%%
%% Note: Since `Node' is a syntax tree, the actual
%% run-time values corresponding to its subtrees may often be partially
%% or completely unknown. Thus, if `Node' represents e.g.
%% "`[... | Ns]'" (where `Ns' is a variable), then
%% the function will return `false', because it is not known
%% whether `Ns' will be bound to a list at run-time. If
%% `Node' instead represents e.g. "`[1, 2, 3]'" or
%% "`[A | []]'", then the function will return
%% `true'.
%%
%% @see list/2

-doc """
Returns `true` if `Node` represents a proper list, and `false` otherwise. A
proper list is a list skeleton either on the form "`[]`" or
"`[*E1*, ..., *En*]`", or "`[... | *Tail*]`" where recursively `Tail` also
represents a proper list.

Note: Since `Node` is a syntax tree, the actual run-time values corresponding to
its subtrees may often be partially or completely unknown. Thus, if `Node`
represents e.g. "`[... | Ns]`" (where `Ns` is a variable), then the function
will return `false`, because it is not known whether `Ns` will be bound to a
list at run-time. If `Node` instead represents e.g. "`[1, 2, 3]`" or
"`[A | []]`", then the function will return `true`.

_See also: _`list/2`.
""".
-spec is_proper_list(syntaxTree()) -> boolean().

is_proper_list(Node) ->
    case type(Node) of
	list ->
	    case list_suffix(Node) of
		none ->
		    true;
		Tail ->
		    is_proper_list(Tail)
	    end;
	nil ->
	    true;
	_ ->
	    false
    end.


%% =====================================================================
%% @doc Returns the list of element subtrees of a list skeleton.
%% `Node' must represent a proper list. E.g., if
%% `Node' represents "<code>[<em>X1</em>, <em>X2</em> |
%% [<em>X3</em>, <em>X4</em> | []]</code>", then
%% `list_elements(Node)' yields the list `[X1, X2, X3, X4]'.
%%
%% @see list/2
%% @see is_proper_list/1

-doc """
Returns the list of element subtrees of a list skeleton. `Node` must represent a
proper list. E.g., if `Node` represents "`[*X1*, *X2* | [*X3*, *X4* | []]`",
then [`list_elements(Node)`](`list_elements/1`) yields the list
`[X1, X2, X3, X4]`.

_See also: _`is_proper_list/1`, `list/2`.
""".
-spec list_elements(syntaxTree()) -> [syntaxTree()].

list_elements(Node) ->
    lists:reverse(list_elements(Node, [])).

list_elements(Node, As) ->
    case type(Node) of
	list ->
	    As1 = lists:reverse(list_prefix(Node)) ++ As,
	    case list_suffix(Node) of
		none ->
		    As1;
		Tail ->
		    list_elements(Tail, As1)
	    end;
	nil ->
	    As
    end.


%% =====================================================================
%% @doc Returns the number of element subtrees of a list skeleton.
%% `Node' must represent a proper list. E.g., if
%% `Node' represents "`[X1 | [X2, X3 | [X4, X5,
%% X6]]]'", then `list_length(Node)' returns the
%% integer 6.
%%
%% Note: this is equivalent to
%% `length(list_elements(Node))', but potentially more
%% efficient.
%%
%% @see list/2
%% @see is_proper_list/1
%% @see list_elements/1

-doc """
Returns the number of element subtrees of a list skeleton. `Node` must represent
a proper list. E.g., if `Node` represents "`[X1 | [X2, X3 | [X4, X5, X6]]]`",
then [`list_length(Node)`](`list_length/1`) returns the integer 6.

Note: this is equivalent to [`length(list_elements(Node))`](`length/1`), but
potentially more efficient.

_See also: _`is_proper_list/1`, `list/2`, `list_elements/1`.
""".
-spec list_length(syntaxTree()) -> non_neg_integer().

list_length(Node) ->
    list_length(Node, 0).

list_length(Node, A) ->
    case type(Node) of
	list ->
	    A1 = length(list_prefix(Node)) + A,
	    case list_suffix(Node) of
		none ->
		    A1;
		Tail ->
		    list_length(Tail, A1)
	    end;
	nil ->
	    A
    end.


%% =====================================================================
%% @doc Expands an abstract list skeleton to its most explicit form. If
%% `Node' represents "<code>[<em>E1</em>, ..., <em>En</em> |
%% <em>Tail</em>]</code>", the result represents "<code>[<em>E1</em> |
%% ... [<em>En</em> | <em>Tail1</em>] ... ]</code>", where
%% `Tail1' is the result of
%% `normalize_list(Tail)'. If `Node' represents
%% "<code>[<em>E1</em>, ..., <em>En</em>]</code>", the result simply
%% represents "<code>[<em>E1</em> | ... [<em>En</em> | []] ...
%% ]</code>". If `Node' does not represent a list skeleton,
%% `Node' itself is returned.
%%
%% @see list/2
%% @see compact_list/1

-doc """
Expands an abstract list skeleton to its most explicit form. If `Node`
represents "`[*E1*, ..., *En* | *Tail*]`", the result represents
"`[*E1* | ... [*En* | *Tail1*] ... ]`", where `Tail1` is the result of
[`normalize_list(Tail)`](`normalize_list/1`). If `Node` represents
"`[*E1*, ..., *En*]`", the result simply represents
"`[*E1* | ... [*En* | []] ... ]`". If `Node` does not represent a list skeleton,
`Node` itself is returned.

_See also: _`compact_list/1`, `list/2`.
""".
-spec normalize_list(syntaxTree()) -> syntaxTree().

normalize_list(Node) ->
    case type(Node) of
	list ->
	    P = list_prefix(Node),
	    case list_suffix(Node) of
		none ->
		    copy_attrs(Node, normalize_list_1(P, nil()));
		Tail ->
		    Tail1 = normalize_list(Tail),
		    copy_attrs(Node, normalize_list_1(P, Tail1))
	    end;
	_ ->
	    Node
    end.

normalize_list_1(Es, Tail) ->
    lists:foldr(fun (X, A) ->
			list([X], A)    % not `cons'!
		end,
		Tail, Es).


%% =====================================================================
%% @doc Yields the most compact form for an abstract list skeleton. The
%% result either represents "<code>[<em>E1</em>, ..., <em>En</em> |
%% <em>Tail</em>]</code>", where `Tail' is not a list
%% skeleton, or otherwise simply "<code>[<em>E1</em>, ...,
%% <em>En</em>]</code>". Annotations on subtrees of `Node'
%% that represent list skeletons may be lost, but comments will be
%% propagated to the result. Returns `Node' itself if
%% `Node' does not represent a list skeleton.
%%
%% @see list/2
%% @see normalize_list/1

-doc """
Yields the most compact form for an abstract list skeleton. The result either
represents "`[*E1*, ..., *En* | *Tail*]`", where `Tail` is not a list skeleton,
or otherwise simply "`[*E1*, ..., *En*]`". Annotations on subtrees of `Node`
that represent list skeletons may be lost, but comments will be propagated to
the result. Returns `Node` itself if `Node` does not represent a list skeleton.

_See also: _`list/2`, `normalize_list/1`.
""".
-spec compact_list(syntaxTree()) -> syntaxTree().

compact_list(Node) ->
    case type(Node) of
	list ->
	    case list_suffix(Node) of
		none ->
		    Node;
		Tail ->
		    case type(Tail) of
			list ->
			    Tail1 = compact_list(Tail),
			    Node1 = list(list_prefix(Node) ++
					 list_prefix(Tail1),
					 list_suffix(Tail1)),
			    join_comments(Tail1,
					  copy_attrs(Node,
						     Node1));
			nil ->
			    Node1 = list(list_prefix(Node)),
			    join_comments(Tail,
					  copy_attrs(Node,
						     Node1));
			_ ->
			    Node 
		    end
	    end;
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Creates an abstract binary-object template. If
%% `Fields' is `[F1, ..., Fn]', the result
%% represents "<code>&lt;&lt;<em>F1</em>, ...,
%% <em>Fn</em>&gt;&gt;</code>".
%%
%% @see binary_fields/1
%% @see binary_field/2

%% type(Node) = binary
%% data(Node) = Fields
%%
%%	Fields = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {bin, Pos, Fields}
%%
%%	Fields = [Field]
%%	Field = {bin_element, ...}
%%
%%	See `binary_field' for documentation on `erl_parse' binary
%%	fields (or "elements").

-doc """
Creates an abstract binary-object template. If `Fields` is `[F1, ..., Fn]`, the
result represents "`<<*F1*, ..., *Fn*>>`".

_See also: _`binary_field/2`, `binary_fields/1`.
""".
-spec binary([syntaxTree()]) -> syntaxTree().

binary(List) ->
    tree(binary, List).

revert_binary(Node) ->
    Pos = get_pos(Node),
    {bin, Pos, binary_fields(Node)}.


%% =====================================================================
%% @doc Returns the list of field subtrees of a `binary' node.
%%
%% @see binary/1
%% @see binary_field/2

-doc """
Returns the list of field subtrees of a `binary` node.

_See also: _`binary/1`, `binary_field/2`.
""".
-spec binary_fields(syntaxTree()) -> [syntaxTree()].

binary_fields(Node) ->
    case unwrap(Node) of
	{bin, _, List} ->
	    List;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @equiv binary_field(Body, [])

-doc "Equivalent to [binary_field(Body, [])](`binary_field/2`).".
-spec binary_field(syntaxTree()) -> syntaxTree().

binary_field(Body) ->
    binary_field(Body, []).


%% =====================================================================
%% @doc Creates an abstract binary template field.
%% If `Size' is `none', this is equivalent to
%% "`binary_field(Body, Types)'", otherwise it is
%% equivalent to "`binary_field(size_qualifier(Body, Size),
%% Types)'".
%%
%% (This is a utility function.)
%%
%% @see binary/1
%% @see binary_field/2
%% @see size_qualifier/2

-doc """
Creates an abstract binary template field. If `Size` is `none`, this is
equivalent to "[`binary_field(Body, Types)`](`binary_field/2`)", otherwise it is
equivalent to
"[`binary_field(size_qualifier(Body, Size), Types)`](`binary_field/2`)".

(This is a utility function.)

_See also: _`binary/1`, `binary_field/2`, `size_qualifier/2`.
""".
-spec binary_field(syntaxTree(), 'none' | syntaxTree(), [syntaxTree()]) ->
        syntaxTree().

binary_field(Body, none, Types) ->
    binary_field(Body, Types);
binary_field(Body, Size, Types) ->
    binary_field(size_qualifier(Body, Size), Types).


%% =====================================================================
%% @doc Creates an abstract binary template field. If
%% `Types' is the empty list, the result simply represents
%% "<code><em>Body</em></code>", otherwise, if `Types' is
%% `[T1, ..., Tn]', the result represents
%% "<code><em>Body</em>/<em>T1</em>-...-<em>Tn</em></code>".
%%
%% @see binary/1
%% @see binary_field/1
%% @see binary_field/3
%% @see binary_field_body/1
%% @see binary_field_types/1
%% @see binary_field_size/1

-record(binary_field, {body :: syntaxTree(), types :: [syntaxTree()]}).

%% type(Node) = binary_field
%% data(Node) = #binary_field{body :: Body, types :: Types}
%%
%%	    Body = syntaxTree()
%%	    Types = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {bin_element, Pos, Expr, Size, TypeList}
%%
%%	Expr = erl_parse()
%%	Size = default | erl_parse()
%%	TypeList = default | [Type] \ []
%%	Type = atom() | {atom(), integer()}

-doc """
Creates an abstract binary template field. If `Types` is the empty list, the
result simply represents "`*Body*`", otherwise, if `Types` is `[T1, ..., Tn]`,
the result represents "`*Body*/*T1*-...-*Tn*`".

_See also: _`binary/1`, `binary_field/1`, `binary_field/3`,
`binary_field_body/1`, `binary_field_size/1`, `binary_field_types/1`.
""".
-spec binary_field(syntaxTree(), [syntaxTree()]) -> syntaxTree().

binary_field(Body, Types) ->
    tree(binary_field, #binary_field{body = Body, types = Types}).

revert_binary_field(Node) ->
    Pos = get_pos(Node),
    Body = binary_field_body(Node),
    {Expr, Size} = case type(Body) of
		       size_qualifier ->
			   %% Note that size qualifiers are not
			   %% revertible out of context.
			   {size_qualifier_body(Body),
			    size_qualifier_argument(Body)};
		       _ ->
			   {Body, default}
		   end,
    Types = case binary_field_types(Node) of
		[] ->
		    default;
		Ts ->
		    fold_binary_field_types(Ts)
	    end,
    {bin_element, Pos, Expr, Size, Types}.


%% =====================================================================
%% @doc Returns the body subtree of a `binary_field'.
%%
%% @see binary_field/2

-doc """
Returns the body subtree of a `binary_field`.

_See also: _`binary_field/2`.
""".
-spec binary_field_body(syntaxTree()) -> syntaxTree().

binary_field_body(Node) ->
    case unwrap(Node) of
	{bin_element, _, Body, Size, _} ->
	    if Size =:= default ->
		    Body;
	       true ->
		    size_qualifier(Body, Size)
	    end;
	Node1 ->
	    (data(Node1))#binary_field.body
    end.


%% =====================================================================
%% @doc Returns the list of type-specifier subtrees of a
%% `binary_field' node. If `Node' represents
%% "<code>.../<em>T1</em>, ..., <em>Tn</em></code>", the result is
%% `[T1, ..., Tn]', otherwise the result is the empty list.
%%
%% @see binary_field/2

-doc """
Returns the list of type-specifier subtrees of a `binary_field` node. If `Node`
represents "`.../*T1*, ..., *Tn*`", the result is `[T1, ..., Tn]`, otherwise the
result is the empty list.

_See also: _`binary_field/2`.
""".
-spec binary_field_types(syntaxTree()) -> [syntaxTree()].

binary_field_types(Node) ->
    case unwrap(Node) of
	{bin_element, Pos, _, _, Types} ->
	    if Types =:= default ->
		    [];
	       true ->
		    unfold_binary_field_types(Types, Pos)
	    end;
	Node1 ->
	    (data(Node1))#binary_field.types
    end.


%% =====================================================================
%% @doc Returns the size specifier subtree of a
%% `binary_field' node, if any. If `Node'
%% represents "<code><em>Body</em>:<em>Size</em></code>" or
%% "<code><em>Body</em>:<em>Size</em>/<em>T1</em>, ...,
%% <em>Tn</em></code>", the result is `Size', otherwise
%% `none' is returned.
%%
%% (This is a utility function.)
%%
%% @see binary_field/2
%% @see binary_field/3

-doc """
Returns the size specifier subtree of a `binary_field` node, if any. If `Node`
represents "`*Body*:*Size*`" or "`*Body*:*Size*/*T1*, ..., *Tn*`", the result is
`Size`, otherwise `none` is returned.

(This is a utility function.)

_See also: _`binary_field/2`, `binary_field/3`.
""".
-spec binary_field_size(syntaxTree()) -> 'none' | syntaxTree().

binary_field_size(Node) ->
    case unwrap(Node) of
	{bin_element, _, _, Size, _} ->
	    if Size =:= default ->
		    none;
	       true ->
		    Size
	    end;
	Node1 ->
	    Body = (data(Node1))#binary_field.body,
	    case type(Body) of
		size_qualifier ->
		    size_qualifier_argument(Body);
		_ ->
		    none
	    end
    end.


%% =====================================================================
%% @doc Creates an abstract size qualifier. The result represents
%% "<code><em>Body</em>:<em>Size</em></code>".
%%
%% @see size_qualifier_body/1
%% @see size_qualifier_argument/1

-record(size_qualifier, {body :: syntaxTree(), size :: syntaxTree()}).

%% type(Node) = size_qualifier
%% data(Node) = #size_qualifier{body :: Body, size :: Size}
%%
%%	Body = Size = syntaxTree()

-doc """
Creates an abstract size qualifier. The result represents "`*Body*:*Size*`".

_See also: _`size_qualifier_argument/1`, `size_qualifier_body/1`.
""".
-spec size_qualifier(syntaxTree(), syntaxTree()) -> syntaxTree().

size_qualifier(Body, Size) ->
    tree(size_qualifier,
	 #size_qualifier{body = Body, size = Size}).


%% =====================================================================
%% @doc Returns the body subtree of a `size_qualifier' node.
%%
%% @see size_qualifier/2

-doc """
Returns the body subtree of a `size_qualifier` node.

_See also: _`size_qualifier/2`.
""".
-spec size_qualifier_body(syntaxTree()) -> syntaxTree().

size_qualifier_body(Node) ->
    (data(Node))#size_qualifier.body.


%% =====================================================================
%% @doc Returns the argument subtree (the size) of a
%% `size_qualifier' node.
%%
%% @see size_qualifier/2

-doc """
Returns the argument subtree (the size) of a `size_qualifier` node.

_See also: _`size_qualifier/2`.
""".
-spec size_qualifier_argument(syntaxTree()) -> syntaxTree().

size_qualifier_argument(Node) ->
    (data(Node))#size_qualifier.size.


%% =====================================================================
%% @doc Creates an abstract error marker. The result represents an
%% occurrence of an error in the source code, with an associated Erlang
%% I/O ErrorInfo structure given by `Error' (see module
%% {@link //stdlib/io} for details). Error markers are regarded as source
%% code forms, but have no defined lexical form.
%%
%% Note: this is supported only for backwards compatibility with
%% existing parsers and tools.
%%
%% @see error_marker_info/1
%% @see warning_marker/1
%% @see eof_marker/0
%% @see is_form/1

%% type(Node) = error_marker
%% data(Node) = term()
%%
%% `erl_parse' representation:
%%
%% {error, Error}
%%
%%	Error = term()
%%
%%	Note that there is no position information for the node
%%	itself: `get_pos' and `set_pos' handle this as a special case.

-doc """
Creates an abstract error marker. The result represents an occurrence of an
error in the source code, with an associated Erlang I/O ErrorInfo structure
given by `Error` (see module [`//stdlib/io`](`m:io`) for details). Error markers
are regarded as source code forms, but have no defined lexical form.

Note: this is supported only for backwards compatibility with existing parsers
and tools.

_See also: _`eof_marker/0`, `error_marker_info/1`, `is_form/1`,
`warning_marker/1`.
""".
-spec error_marker(term()) -> syntaxTree().

error_marker(Error) ->
    tree(error_marker, Error).

revert_error_marker(Node) ->
    %% Note that the position information of the node itself is not
    %% preserved.
    {error, error_marker_info(Node)}.


%% =====================================================================
%% @doc Returns the ErrorInfo structure of an `error_marker' node.
%%
%% @see error_marker/1

-doc """
Returns the ErrorInfo structure of an `error_marker` node.

_See also: _`error_marker/1`.
""".
-spec error_marker_info(syntaxTree()) -> term().

error_marker_info(Node) ->
    case unwrap(Node) of
	{error, Error} ->
	    Error;
	T ->
	    data(T)
    end.


%% =====================================================================
%% @doc Creates an abstract warning marker. The result represents an
%% occurrence of a possible problem in the source code, with an
%% associated Erlang I/O ErrorInfo structure given by `Error'
%% (see module {@link //stdlib/io} for details). Warning markers are
%% regarded as source code forms, but have no defined lexical form.
%%
%% Note: this is supported only for backwards compatibility with
%% existing parsers and tools.
%%
%% @see warning_marker_info/1
%% @see error_marker/1
%% @see eof_marker/0
%% @see is_form/1

%% type(Node) = warning_marker
%% data(Node) = term()
%%
%% `erl_parse' representation:
%%
%% {warning, Error}
%%
%%	Error = term()
%%
%%	Note that there is no position information for the node
%%	itself: `get_pos' and `set_pos' handle this as a special case.

-doc """
Creates an abstract warning marker. The result represents an occurrence of a
possible problem in the source code, with an associated Erlang I/O ErrorInfo
structure given by `Error` (see module [`//stdlib/io`](`m:io`) for details).
Warning markers are regarded as source code forms, but have no defined lexical
form.

Note: this is supported only for backwards compatibility with existing parsers
and tools.

_See also: _`eof_marker/0`, `error_marker/1`, `is_form/1`,
`warning_marker_info/1`.
""".
-spec warning_marker(term()) -> syntaxTree().

warning_marker(Warning) ->
    tree(warning_marker, Warning).

revert_warning_marker(Node) ->
    %% Note that the position information of the node itself is not
    %% preserved.
    {warning, warning_marker_info(Node)}.


%% =====================================================================
%% @doc Returns the ErrorInfo structure of a `warning_marker' node.
%%
%% @see warning_marker/1

-doc """
Returns the ErrorInfo structure of a `warning_marker` node.

_See also: _`warning_marker/1`.
""".
-spec warning_marker_info(syntaxTree()) -> term().

warning_marker_info(Node) ->
    case unwrap(Node) of
	{warning, Error} ->
	    Error;
	T ->
	    data(T)
    end.


%% =====================================================================
%% @doc Creates an abstract end-of-file marker. This represents the
%% end of input when reading a sequence of source code forms. An
%% end-of-file marker is itself regarded as a source code form
%% (namely, the last in any sequence in which it occurs). It has no
%% defined lexical form.
%%
%% Note: this is retained only for backwards compatibility with
%% existing parsers and tools.
%%
%% @see error_marker/1
%% @see warning_marker/1
%% @see is_form/1

%% type(Node) = eof_marker
%% data(Node) = term()
%%
%% `erl_parse' representation:
%%
%% {eof, Pos}

-doc """
Creates an abstract end-of-file marker. This represents the end of input when
reading a sequence of source code forms. An end-of-file marker is itself
regarded as a source code form (namely, the last in any sequence in which it
occurs). It has no defined lexical form.

Note: this is retained only for backwards compatibility with existing parsers
and tools.

_See also: _`error_marker/1`, `is_form/1`, `warning_marker/1`.
""".
-spec eof_marker() -> syntaxTree().

eof_marker() ->
    tree(eof_marker).

revert_eof_marker(Node) ->
    Pos = get_pos(Node),
    {eof, Pos}.


%% =====================================================================
%% @equiv attribute(Name, none)

-doc "Equivalent to [attribute(Name, none)](`attribute/2`).".
-spec attribute(syntaxTree()) -> syntaxTree().

attribute(Name) ->
    attribute(Name, none).


%% =====================================================================
%% @doc Creates an abstract program attribute. If
%% `Arguments' is `[A1, ..., An]', the result
%% represents "<code>-<em>Name</em>(<em>A1</em>, ...,
%% <em>An</em>).</code>". Otherwise, if `Arguments' is
%% `none', the result represents
%% "<code>-<em>Name</em>.</code>". The latter form makes it possible
%% to represent preprocessor directives such as
%% "`-endif.'". Attributes are source code forms.
%%
%% Note: The preprocessor macro definition directive
%% "<code>-define(<em>Name</em>, <em>Body</em>).</code>" has relatively
%% few requirements on the syntactical form of `Body' (viewed
%% as a sequence of tokens). The `text' node type can be used
%% for a `Body' that is not a normal Erlang construct.
%%
%% @see attribute/1
%% @see attribute_name/1
%% @see attribute_arguments/1
%% @see text/1
%% @see is_form/1

-record(attribute, {name :: syntaxTree(), args :: 'none' | [syntaxTree()]}).

%% type(Node) = attribute
%% data(Node) = #attribute{name :: Name, args :: Arguments}
%%
%%	Name = syntaxTree()
%%	Arguments = none | [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {attribute, Pos, module, {Name,Vars}}
%% {attribute, Pos, module, Name}
%%
%%	Name = atom() | [atom()]
%%	Vars = [atom()]
%%
%%	Representing `-module(M).', or `-module(M, Vs).', where M is
%%	`A1.A2.....An' if Name is `[A1, A2, ..., An]', and Vs is `[V1,
%%	..., Vm]' if Vars is `[V1, ..., Vm]'.
%%
%% {attribute, Pos, export, Exports}
%%
%%	Exports = [{atom(), integer()}]
%%
%%	Representing `-export([A1/N1, ..., Ak/Nk]).', if `Exports' is
%%	`[{A1, N1}, ..., {Ak, Nk}]'.
%%
%% {attribute, Pos, import, Imports}
%%
%%	Imports = {atom(), Pairs} | [atom()]
%%	Pairs = [{atom(), integer()]
%%
%%	Representing `-import(Module, [A1/N1, ..., Ak/Nk]).', if
%%	`Imports' is `{Module, [{A1, N1}, ..., {Ak, Nk}]}', or
%%	`-import(A1.....An).', if `Imports' is `[A1, ..., An]'.
%%
%% {attribute, Pos, export_type, ExportedTypes}
%%
%%	ExportedTypes = [{atom(), integer()}]
%%
%%	Representing `-export_type([N1/A1, ..., Nk/Ak]).',
%%      if `ExportedTypes' is `[{N1, A1}, ..., {Nk, Ak}]'.
%%
%% {attribute, Pos, optional_callbacks, OptionalCallbacks}
%%
%%	OptionalCallbacks = [{atom(), integer()}]
%%
%%	Representing `-optional_callbacks([A1/N1, ..., Ak/Nk]).',
%%      if `OptionalCallbacks' is `[{A1, N1}, ..., {Ak, Nk}]'.
%%
%% {attribute, Pos, SpecTag, {FuncSpec, FuncType}}
%%
%%      SpecTag = spec | callback
%%	FuncSpec = {module(), atom(), arity()} | {atom(), arity()}
%%      FuncType = a (possibly constrained) function type
%%
%%	Representing `-SpecTag M:F/A Ft1; ...; Ftk.' or
%%      `-SpecTag F/A Ft1; ...; Ftk.', if `FuncTypes' is
%%      `[Ft1, ..., Ftk]'.
%%
%% {attribute, Pos, TypeTag, {Name, Type, Parameters}}
%%
%%      TypeTag = type | opaque
%%      Type = a type
%%      Parameters = [Variable]
%%
%%	Representing `-TypeTag Name(V1, ..., Vk) :: Type .'
%%      if `Parameters' is `[V1, ..., Vk]'.
%%
%% {attribute, Pos, file, Position}
%%
%%	Position = {filename(), integer()}
%%
%%	Representing `-file(Name, Line).', if `Position' is `{Name,
%%	Line}'.
%%
%% {attribute, Pos, record, Info}
%%
%%	Info = {Name, [Entries]}
%%	Name = atom()
%%
%%	Entries = UntypedEntries
%%              | {typed_record_field, UntypedEntries, Type}
%%      UntypedEntries = {record_field, Pos, atom()}
%%                     | {record_field, Pos, atom(), erl_parse()}
%%
%%      Representing `-record(Name, {<F1>, ..., <Fn>}).', if `Info' is
%%	`{Name, [D1, ..., D1]}', where each `Fi' is either `Ai = <Ei>',
%%	if the corresponding `Di' is `{record_field, Pos, Ai, Ei}', or
%%	otherwise simply `Ai', if `Di' is `{record_field, Pos, Ai}', or
%%      `Ai = <Ei> :: <Ti>', if `Di' is `{typed_record_field,
%%      {record_field, Pos, Ai, Ei}, Ti}', or `Ai :: <Ti>', if `Di' is
%%      `{typed_record_field, {record_field, Pos, Ai}, Ti}'.
%%
%% {attribute, L, Name, Term}
%%
%%	Name = atom() \ StandardName
%%	StandardName = module | export | import | file | record
%%	Term = term()
%%
%%	Representing `-Name(Term).'.

-doc """
Creates an abstract program attribute. If `Arguments` is `[A1, ..., An]`, the
result represents "`-*Name*(*A1*, ..., *An*).`". Otherwise, if `Arguments` is
`none`, the result represents "`-*Name*.`". The latter form makes it possible to
represent preprocessor directives such as "`-endif.`". Attributes are source
code forms.

Note: The preprocessor macro definition directive "`-define(*Name*, *Body*).`"
has relatively few requirements on the syntactical form of `Body` (viewed as a
sequence of tokens). The `text` node type can be used for a `Body` that is not a
normal Erlang construct.

_See also: _`attribute/1`, `attribute_arguments/1`, `attribute_name/1`,
`is_form/1`, `text/1`.
""".
-spec attribute(syntaxTree(), 'none' | [syntaxTree()]) -> syntaxTree().

attribute(Name, Args) ->
    tree(attribute, #attribute{name = Name, args = Args}).

revert_attribute(Node) ->
    Name = attribute_name(Node),
    Args = attribute_arguments(Node),
    Pos = get_pos(Node),
    case type(Name) of
	atom ->
	    revert_attribute_1(atom_value(Name), Args, Pos, Node);
	_ ->
	    Node
    end.

%% All the checking makes this part a bit messy:

revert_attribute_1(module, [M], Pos, Node) ->
    case revert_module_name(M) of
	{ok, A} -> 
	    {attribute, Pos, module, A};
	error -> Node
    end;
revert_attribute_1(module, [M, List], Pos, Node) ->
    Vs = case is_list_skeleton(List) of
	     true ->
		 case is_proper_list(List) of
		     true ->
			 fold_variable_names(list_elements(List));
		     false ->
			 Node
		 end;
	     false ->
		 Node
	 end,
    case revert_module_name(M) of
	{ok, A} -> 
	    {attribute, Pos, module, {A, Vs}};
	error -> Node
    end;
revert_attribute_1(export, [List], Pos, Node) ->
    case is_list_skeleton(List) of
	true ->
	    case is_proper_list(List) of
		true ->
		    Fs = fold_function_names(list_elements(List)),
		    {attribute, Pos, export, Fs};
		false ->
		    Node
	    end;
	false ->
	    Node
    end;
revert_attribute_1(import, [M], Pos, Node) ->
    case revert_module_name(M) of
	{ok, A} -> {attribute, Pos, import, A};
	error -> Node
    end;
revert_attribute_1(import, [M, List], Pos, Node) ->
    case revert_module_name(M) of
	{ok, A} ->
	    case is_list_skeleton(List) of
		true ->
		    case is_proper_list(List) of
			true ->
			    Fs = fold_function_names(
				   list_elements(List)),
			    {attribute, Pos, import, {A, Fs}};
			false ->
			    Node
		    end;
		false ->
		    Node
	    end;
	error ->
	    Node
    end;
revert_attribute_1(file, [A, Line], Pos, Node) ->
    case type(A) of
	string ->
	    case type(Line) of
		integer ->
		    {attribute, Pos, file,
		     {concrete(A), concrete(Line)}};
		_ ->
		    Node
	    end;
	_ ->
	    Node
    end;
revert_attribute_1(record, [A, Tuple], Pos, Node) ->
    case type(A) of
	atom ->
	    case type(Tuple) of
		tuple ->
		    Fs = fold_record_fields(
			   tuple_elements(Tuple)),
		    {attribute, Pos, record, {concrete(A), Fs}};
		_ ->
		    Node
	    end;
	_ ->
	    Node
    end;
revert_attribute_1(N, [T], Pos, _) ->
    {attribute, Pos, N, concrete(T)};
revert_attribute_1(_, _, _, Node) ->
    Node.

revert_module_name(A) ->
    case type(A) of
	atom ->
	    {ok, concrete(A)};
	_ ->
	    error
    end.


%% =====================================================================
%% @doc Returns the name subtree of an `attribute' node.
%%
%% @see attribute/1

-doc """
Returns the name subtree of an `attribute` node.

_See also: _`attribute/1`.
""".
-spec attribute_name(syntaxTree()) -> syntaxTree().

attribute_name(Node) ->
    case unwrap(Node) of
	{attribute, Pos, Name, _} ->
	    set_pos(atom(Name), Pos);
	Node1 ->
	    (data(Node1))#attribute.name
    end.


%% =====================================================================
%% @doc Returns the list of argument subtrees of an
%% `attribute' node, if any. If `Node'
%% represents "<code>-<em>Name</em>.</code>", the result is
%% `none'. Otherwise, if `Node' represents
%% "<code>-<em>Name</em>(<em>E1</em>, ..., <em>En</em>).</code>",
%% `[E1, ..., E1]' is returned.
%%
%% @see attribute/1

-doc """
Returns the list of argument subtrees of an `attribute` node, if any. If `Node`
represents "`-*Name*.`", the result is `none`. Otherwise, if `Node` represents
"`-*Name*(*E1*, ..., *En*).`", `[E1, ..., E1]` is returned.

_See also: _`attribute/1`.
""".
-spec attribute_arguments(syntaxTree()) -> none | [syntaxTree()].

attribute_arguments(Node) ->
    case unwrap(Node) of
	{attribute, Pos, Name, Data} ->
	    case Name of
		module ->
		    {M1, Vs} =
			case Data of
			    {M0, Vs0} ->
				{M0, unfold_variable_names(Vs0, Pos)};
			    M0 ->
				{M0, none}
			end,
		    M2 = atom(M1),
		    M = set_pos(M2, Pos),
		    if Vs == none -> [M];
		       true -> [M, set_pos(list(Vs), Pos)]
		    end;
		export ->
		    [set_pos(
		       list(unfold_function_names(Data, Pos)),
		       Pos)];
		import ->
		    {Module, Imports} = Data,
		    [set_pos(atom(Module), Pos),
		     set_pos(
		       list(unfold_function_names(Imports, Pos)),
		       Pos)];
		file ->
		    {File, Line} = Data,
		    [set_pos(string(File), Pos),
		     set_pos(integer(Line), Pos)];
		record ->
		    %% Note that we create a tuple as container
		    %% for the second argument!
		    {Type, Entries} = Data,
		    [set_pos(atom(Type), Pos),
		     set_pos(tuple(unfold_record_fields(Entries)),
			     Pos)];
		_ ->
		    %% Standard single-term generic attribute.
		    [set_pos(abstract(Data), Pos)]
	    end;
	Node1 ->
	    (data(Node1))#attribute.args
    end.


%% =====================================================================
%% @doc Creates an abstract arity qualifier. The result represents
%% "<code><em>Body</em>/<em>Arity</em></code>".
%%
%% @see arity_qualifier_body/1
%% @see arity_qualifier_argument/1

-record(arity_qualifier, {body :: syntaxTree(), arity :: syntaxTree()}).

%% type(Node) = arity_qualifier
%% data(Node) = #arity_qualifier{body :: Body, arity :: Arity}
%%
%%	Body = Arity = syntaxTree()

-doc """
Creates an abstract arity qualifier. The result represents "`*Body*/*Arity*`".

_See also: _`arity_qualifier_argument/1`, `arity_qualifier_body/1`.
""".
-spec arity_qualifier(syntaxTree(), syntaxTree()) -> syntaxTree().

arity_qualifier(Body, Arity) ->
    tree(arity_qualifier,
	 #arity_qualifier{body = Body, arity = Arity}).


%% =====================================================================
%% @doc Returns the body subtree of an `arity_qualifier' node.
%%
%% @see arity_qualifier/2

-doc """
Returns the body subtree of an `arity_qualifier` node.

_See also: _`arity_qualifier/2`.
""".
-spec arity_qualifier_body(syntaxTree()) -> syntaxTree().

arity_qualifier_body(Node) ->
    (data(Node))#arity_qualifier.body.


%% =====================================================================
%% @doc Returns the argument (the arity) subtree of an
%% `arity_qualifier' node.
%%
%% @see arity_qualifier/2

-doc """
Returns the argument (the arity) subtree of an `arity_qualifier` node.

_See also: _`arity_qualifier/2`.
""".
-spec arity_qualifier_argument(syntaxTree()) -> syntaxTree().

arity_qualifier_argument(Node) ->
    (data(Node))#arity_qualifier.arity.


%% =====================================================================
%% @doc Creates an abstract module qualifier. The result represents
%% "<code><em>Module</em>:<em>Body</em></code>".
%%
%% @see module_qualifier_argument/1
%% @see module_qualifier_body/1

-record(module_qualifier, {module :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = module_qualifier
%% data(Node) = #module_qualifier{module :: Module, body :: Body}
%%
%%	Module = Body = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {remote, Pos, Module, Arg}
%%
%%	Module = Arg = erl_parse()

-doc """
Creates an abstract module qualifier. The result represents "`*Module*:*Body*`".

_See also: _`module_qualifier_argument/1`, `module_qualifier_body/1`.
""".
-spec module_qualifier(syntaxTree(), syntaxTree()) -> syntaxTree().

module_qualifier(Module, Body) ->
    tree(module_qualifier,
	 #module_qualifier{module = Module, body = Body}).

revert_module_qualifier(Node) ->
    Pos = get_pos(Node),
    Module = module_qualifier_argument(Node),
    Body = module_qualifier_body(Node),
    {remote, Pos, Module, Body}.


%% =====================================================================
%% @doc Returns the argument (the module) subtree of a
%% `module_qualifier' node.
%%
%% @see module_qualifier/2

-doc """
Returns the argument (the module) subtree of a `module_qualifier` node.

_See also: _`module_qualifier/2`.
""".
-spec module_qualifier_argument(syntaxTree()) -> syntaxTree().

module_qualifier_argument(Node) ->
    case unwrap(Node) of
	{remote, _, Module, _} ->
	    Module;
	Node1 ->
	    (data(Node1))#module_qualifier.module
    end.


%% =====================================================================
%% @doc Returns the body subtree of a `module_qualifier' node.
%%
%% @see module_qualifier/2

-doc """
Returns the body subtree of a `module_qualifier` node.

_See also: _`module_qualifier/2`.
""".
-spec module_qualifier_body(syntaxTree()) -> syntaxTree().

module_qualifier_body(Node) ->
    case unwrap(Node) of
	{remote, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#module_qualifier.body
    end.


%% =====================================================================
%% @doc Creates an abstract function definition. If `Clauses'
%% is `[C1, ..., Cn]', the result represents
%% "<code><em>Name</em> <em>C1</em>; ...; <em>Name</em>
%% <em>Cn</em>.</code>". More exactly, if each `Ci'
%% represents "<code>(<em>Pi1</em>, ..., <em>Pim</em>) <em>Gi</em> ->
%% <em>Bi</em></code>", then the result represents
%% "<code><em>Name</em>(<em>P11</em>, ..., <em>P1m</em>) <em>G1</em> ->
%% <em>B1</em>; ...; <em>Name</em>(<em>Pn1</em>, ..., <em>Pnm</em>)
%% <em>Gn</em> -> <em>Bn</em>.</code>". Function definitions are source
%% code forms.
%%
%% @see function_name/1
%% @see function_clauses/1
%% @see function_arity/1
%% @see is_form/1

%% Don't use the name 'function' for this record, to avoid confusion with
%% the tuples on the form {function,Name,Arity} used by erl_parse.
-record(func, {name :: syntaxTree(), clauses :: [syntaxTree()]}).

%% type(Node) = function
%% data(Node) = #func{name :: Name, clauses :: Clauses}
%%
%%	Name = syntaxTree()
%%	Clauses = [syntaxTree()]
%%
%%	(There's no real point in precomputing and storing the arity,
%%	and passing it as a constructor argument makes it possible to
%%	end up with an inconsistent value. Besides, some people might
%%	want to check all clauses, and not just the first, so the
%%	computation is not obvious.)
%%
%% `erl_parse' representation:
%%
%% {function, Pos, Name, Arity, Clauses}
%%
%%	Name = atom()
%%	Arity = integer()
%%	Clauses = [Clause] \ []
%%	Clause = {clause, ...}
%%
%%	where the number of patterns in each clause should be equal to
%%	the integer `Arity'; see `clause' for documentation on
%%	`erl_parse' clauses.

-doc """
Creates an abstract function definition. If `Clauses` is `[C1, ..., Cn]`, the
result represents "`*Name**C1*; ...; *Name**Cn*.`". More exactly, if each `Ci`
represents "`(*Pi1*, ..., *Pim*) *Gi* -> *Bi*`", then the result represents
"`*Name*(*P11*, ..., *P1m*) *G1* -> *B1*; ...; *Name*(*Pn1*, ..., *Pnm*) *Gn* -> *Bn*.`".
Function definitions are source code forms.

_See also: _`function_arity/1`, `function_clauses/1`, `function_name/1`,
`is_form/1`.
""".
-spec function(syntaxTree(), [syntaxTree()]) -> syntaxTree().

function(Name, Clauses) ->
    tree(function, #func{name = Name, clauses = Clauses}).

revert_function(Node) ->
    Name = function_name(Node),
    Clauses = [revert_clause(C) || C <- function_clauses(Node)],
    Pos = get_pos(Node),
    case type(Name) of
	atom ->
	    A = function_arity(Node),
	    {function, Pos, concrete(Name), A, Clauses};
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the name subtree of a `function' node.
%%
%% @see function/2

-doc """
Returns the name subtree of a `function` node.

_See also: _`function/2`.
""".
-spec function_name(syntaxTree()) -> syntaxTree().

function_name(Node) ->
    case unwrap(Node) of
	{function, Pos, Name, _, _} ->
	    set_pos(atom(Name), Pos);
	Node1 ->
	    (data(Node1))#func.name
    end.


%% =====================================================================
%% @doc Returns the list of clause subtrees of a `function' node.
%%
%% @see function/2

-doc """
Returns the list of clause subtrees of a `function` node.

_See also: _`function/2`.
""".
-spec function_clauses(syntaxTree()) -> [syntaxTree()].

function_clauses(Node) ->
    case unwrap(Node) of
	{function, _, _, _, Clauses} ->
	    Clauses;
	Node1 ->
	    (data(Node1))#func.clauses
    end.


%% =====================================================================
%% @doc Returns the arity of a `function' node. The result
%% is the number of parameter patterns in the first clause of the
%% function; subsequent clauses are ignored.
%%
%% An exception is thrown if `function_clauses(Node)'
%% returns an empty list, or if the first element of that list is not
%% a syntax tree `C' of type `clause' such that
%% `clause_patterns(C)' is a nonempty list.
%%
%% @see function/2
%% @see function_clauses/1
%% @see clause/3
%% @see clause_patterns/1

-doc """
Returns the arity of a `function` node. The result is the number of parameter
patterns in the first clause of the function; subsequent clauses are ignored.

An exception is thrown if [`function_clauses(Node)`](`function_clauses/1`)
returns an empty list, or if the first element of that list is not a syntax tree
`C` of type `clause` such that [`clause_patterns(C)`](`clause_patterns/1`) is a
nonempty list.

_See also: _`clause/3`, `clause_patterns/1`, `function/2`, `function_clauses/1`.
""".
-spec function_arity(syntaxTree()) -> arity().

function_arity(Node) ->
    %% Note that this never accesses the arity field of `erl_parse'
    %% function nodes.
    length(clause_patterns(hd(function_clauses(Node)))).


%% =====================================================================
%% @equiv clause([], Guard, Body)

-type guard() :: 'none' | syntaxTree() | [syntaxTree()] | [[syntaxTree()]].

-doc "Equivalent to [clause([], Guard, Body)](`clause/3`).".
-spec clause(guard(), [syntaxTree()]) -> syntaxTree().

clause(Guard, Body) ->
    clause([], Guard, Body).


%% =====================================================================
%% @doc Creates an abstract clause. If `Patterns' is
%% `[P1, ..., Pn]' and `Body' is `[B1, ...,
%% Bm]', then if `Guard' is `none', the
%% result represents "<code>(<em>P1</em>, ..., <em>Pn</em>) ->
%% <em>B1</em>, ..., <em>Bm</em></code>", otherwise, unless
%% `Guard' is a list, the result represents
%% "<code>(<em>P1</em>, ..., <em>Pn</em>) when <em>Guard</em> ->
%% <em>B1</em>, ..., <em>Bm</em></code>".
%%
%% For simplicity, the `Guard' argument may also be any
%% of the following:
%% <ul>
%%   <li>An empty list `[]'. This is equivalent to passing
%%       `none'.</li>
%%   <li>A nonempty list `[E1, ..., Ej]' of syntax trees.
%%       This is equivalent to passing `conjunction([E1, ...,
%%       Ej])'.</li>
%%   <li>A nonempty list of lists of syntax trees `[[E1_1, ...,
%%       E1_k1], ..., [Ej_1, ..., Ej_kj]]', which is equivalent
%%       to passing `disjunction([conjunction([E1_1, ...,
%%       E1_k1]), ..., conjunction([Ej_1, ..., Ej_kj])])'.</li>
%% </ul>
%%
%% @see clause/2
%% @see clause_patterns/1
%% @see clause_guard/1
%% @see clause_body/1

-record(clause, {patterns :: [syntaxTree()],
		 guard    :: guard(),
		 body     :: [syntaxTree()]}).

%% type(Node) = clause
%% data(Node) = #clause{patterns :: Patterns, guard :: Guard,
%%		        body :: Body}
%%
%%	Patterns = [syntaxTree()]
%%	Guard = syntaxTree() | none
%%	Body = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {clause, Pos, Patterns, Guard, Body}
%%
%%	Patterns = [erl_parse()]
%%	Guard = [[erl_parse()]] | [erl_parse()]
%%	Body = [erl_parse()] \ []
%%
%%	Taken out of context, if `Patterns' is `[P1, ..., Pn]' and
%%	`Body' is `[B1, ..., Bm]', this represents `(<P1>, ..., <Pn>) ->
%%	<B1>, ..., <Bm>' if `Guard' is `[]', or otherwise `(<P1>, ...,
%%	<Pn>) when <G> -> <Body>', where `G' is `<E1_1>, ..., <E1_k1>;
%%	...; <Ej_1>, ..., <Ej_kj>', if `Guard' is a list of lists
%%	`[[E1_1, ..., E1_k1], ..., [Ej_1, ..., Ej_kj]]'. In older
%%	versions, `Guard' was simply a list `[E1, ..., En]' of parse
%%	trees, which is equivalent to the new form `[[E1, ..., En]]'.

-doc """
Creates an abstract clause. If `Patterns` is `[P1, ..., Pn]` and `Body` is
`[B1, ..., Bm]`, then if `Guard` is `none`, the result represents
"`(*P1*, ..., *Pn*) -> *B1*, ..., *Bm*`", otherwise, unless `Guard` is a list,
the result represents "`(*P1*, ..., *Pn*) when *Guard* -> *B1*, ..., *Bm*`".

For simplicity, the `Guard` argument may also be any of the following:

- An empty list `[]`. This is equivalent to passing `none`.
- A nonempty list `[E1, ..., Ej]` of syntax trees. This is equivalent to passing
  `conjunction([E1, ..., Ej])`.
- A nonempty list of lists of syntax trees
  `[[E1_1, ..., E1_k1], ..., [Ej_1, ..., Ej_kj]]`, which is equivalent to
  passing
  `disjunction([conjunction([E1_1, ..., E1_k1]), ..., conjunction([Ej_1, ..., Ej_kj])])`.

_See also: _`clause/2`, `clause_body/1`, `clause_guard/1`, `clause_patterns/1`.
""".
-spec clause([syntaxTree()], guard(), [syntaxTree()]) -> syntaxTree().

clause(Patterns, Guard, Body) ->
    Guard1 = case Guard of
		 [] ->
		     none;
		 [X | _] when is_list(X) ->
		     disjunction(conjunction_list(Guard));
		 [_ | _] ->
		     %% Handle older forms also.
		     conjunction(Guard);
		 _ ->
		     %% This should be `none' or a syntax tree.
		     Guard
	     end,
    tree(clause, #clause{patterns = Patterns, guard = Guard1,
			 body = Body}).

conjunction_list([L | Ls]) ->
    [conjunction(L) | conjunction_list(Ls)];
conjunction_list([]) ->
    [].

revert_clause(Node) ->
    Pos = get_pos(Node),
    Guard = case clause_guard(Node) of
		none ->
		    [];
		E ->
		    case type(E) of
			disjunction ->
			    revert_clause_disjunction(E);
			conjunction ->
			    %% Only the top level expression is
			    %% unfolded here; no recursion.
			    [conjunction_body(E)];
			_ ->
			    [[E]]	% a single expression
		    end
	    end,
    {clause, Pos, clause_patterns(Node), Guard,
     clause_body(Node)}.

revert_clause_disjunction(D) ->
    %% We handle conjunctions within a disjunction, but only at
    %% the top level; no recursion.
    [case type(E) of
	 conjunction ->
	     conjunction_body(E);
	 _ ->
	     [E]
     end
     || E <- disjunction_body(D)].

revert_try_clause(Node) ->
    fold_try_clause(revert_clause(Node)).

fold_try_clause({clause, Pos, [P], Guard, Body}) ->
    P1 = case type(P) of
	     class_qualifier ->
		 {tuple, Pos, [class_qualifier_argument(P),
			       class_qualifier_body(P),
			       class_qualifier_stacktrace(P)]};
	     _ ->
		 {tuple, Pos, [{atom, Pos, throw}, P, {var, Pos, '_'}]}
	 end,
    {clause, Pos, [P1], Guard, Body}.

unfold_try_clauses(Cs) ->
    [unfold_try_clause(C) || C <- Cs].

unfold_try_clause({clause, Pos, [{tuple, _, [{atom, _, throw},
                                             V,
                                             {var, _, '_'}]}],
		   Guard, Body}) ->
    {clause, Pos, [V], Guard, Body};
unfold_try_clause({clause, Pos, [{tuple, _, [C, V, Stacktrace]}],
		   Guard, Body}) ->
    {clause, Pos, [class_qualifier(C, V, Stacktrace)], Guard, Body}.


%% =====================================================================
%% @doc Returns the list of pattern subtrees of a `clause' node.
%%
%% @see clause/3

-doc """
Returns the list of pattern subtrees of a `clause` node.

_See also: _`clause/3`.
""".
-spec clause_patterns(syntaxTree()) -> [syntaxTree()].

clause_patterns(Node) ->
    case unwrap(Node) of
	{clause, _, Patterns, _, _} ->
	    Patterns;
	Node1 ->
	    (data(Node1))#clause.patterns
    end.


%% =====================================================================
%% @doc Returns the guard subtree of a `clause' node, if
%% any. If `Node' represents "<code>(<em>P1</em>, ...,
%% <em>Pn</em>) when <em>Guard</em> -> <em>B1</em>, ...,
%% <em>Bm</em></code>", `Guard' is returned. Otherwise, the
%% result is `none'.
%%
%% @see clause/3

-doc """
Returns the guard subtree of a `clause` node, if any. If `Node` represents
"`(*P1*, ..., *Pn*) when *Guard* -> *B1*, ..., *Bm*`", `Guard` is returned.
Otherwise, the result is `none`.

_See also: _`clause/3`.
""".
-spec clause_guard(syntaxTree()) -> 'none' | syntaxTree().

clause_guard(Node) ->
    case unwrap(Node) of
	{clause, _, _, Guard, _} ->
	    case Guard of
		[] -> none;
		[L | _] when is_list(L) ->
		    disjunction(conjunction_list(Guard));
		[_ | _] ->
		    conjunction(Guard)
	    end;
	Node1 ->
	    (data(Node1))#clause.guard
    end.


%% =====================================================================
%% @doc Return the list of body subtrees of a `clause' node.
%%
%% @see clause/3

-doc """
Return the list of body subtrees of a `clause` node.

_See also: _`clause/3`.
""".
-spec clause_body(syntaxTree()) -> [syntaxTree()].

clause_body(Node) ->
    case unwrap(Node) of
	{clause, _, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#clause.body
    end.


%% =====================================================================
%% @doc Creates an abstract disjunction. If `List' is
%% `[E1, ..., En]', the result represents
%% "<code><em>E1</em>; ...; <em>En</em></code>".
%%
%% @see disjunction_body/1
%% @see conjunction/1

%% type(Node) = disjunction
%% data(Node) = [syntaxTree()]

-doc """
Creates an abstract disjunction. If `List` is `[E1, ..., En]`, the result
represents "`*E1*; ...; *En*`".

_See also: _`conjunction/1`, `disjunction_body/1`.
""".
-spec disjunction([syntaxTree()]) -> syntaxTree().

disjunction(Tests) ->
    tree(disjunction, Tests).


%% =====================================================================
%% @doc Returns the list of body subtrees of a
%% `disjunction' node.
%%
%% @see disjunction/1

-doc """
Returns the list of body subtrees of a `disjunction` node.

_See also: _`disjunction/1`.
""".
-spec disjunction_body(syntaxTree()) -> [syntaxTree()].

disjunction_body(Node) ->
    data(Node).


%% =====================================================================
%% @doc Creates an abstract conjunction. If `List' is
%% `[E1, ..., En]', the result represents
%% "<code><em>E1</em>, ..., <em>En</em></code>".
%%
%% @see conjunction_body/1
%% @see disjunction/1

%% type(Node) = conjunction
%% data(Node) = [syntaxTree()]

-doc """
Creates an abstract conjunction. If `List` is `[E1, ..., En]`, the result
represents "`*E1*, ..., *En*`".

_See also: _`conjunction_body/1`, `disjunction/1`.
""".
-spec conjunction([syntaxTree()]) -> syntaxTree().

conjunction(Tests) ->
    tree(conjunction, Tests).


%% =====================================================================
%% @doc Returns the list of body subtrees of a
%% `conjunction' node.
%%
%% @see conjunction/1

-doc """
Returns the list of body subtrees of a `conjunction` node.

_See also: _`conjunction/1`.
""".
-spec conjunction_body(syntaxTree()) -> [syntaxTree()].

conjunction_body(Node) ->
    data(Node).


%% =====================================================================
%% @doc Creates an abstract catch-expression. The result represents
%% "<code>catch <em>Expr</em></code>".
%%
%% @see catch_expr_body/1

%% type(Node) = catch_expr
%% data(Node) = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {'catch', Pos, Expr}
%%
%%	Expr = erl_parse()

-doc """
Creates an abstract catch-expression. The result represents "`catch *Expr*`".

_See also: _`catch_expr_body/1`.
""".
-spec catch_expr(syntaxTree()) -> syntaxTree().

catch_expr(Expr) ->
    tree(catch_expr, Expr).

revert_catch_expr(Node) ->
    Pos = get_pos(Node),
    Expr = catch_expr_body(Node),
    {'catch', Pos, Expr}.


%% =====================================================================
%% @doc Returns the body subtree of a `catch_expr' node.
%%
%% @see catch_expr/1

-doc """
Returns the body subtree of a `catch_expr` node.

_See also: _`catch_expr/1`.
""".
-spec catch_expr_body(syntaxTree()) -> syntaxTree().

catch_expr_body(Node) ->
    case unwrap(Node) of
	{'catch', _, Expr} ->
	    Expr;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract match-expression. The result represents
%% "<code><em>Pattern</em> = <em>Body</em></code>".
%%
%% @see match_expr_pattern/1
%% @see match_expr_body/1

-record(match_expr, {pattern :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = match_expr
%% data(Node) = #match_expr{pattern :: Pattern, body :: Body}
%%
%%	Pattern = Body = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {match, Pos, Pattern, Body}
%%
%%	Pattern = Body = erl_parse()

-doc """
Creates an abstract match-expression. The result represents
"`*Pattern* = *Body*`".

_See also: _`match_expr_body/1`, `match_expr_pattern/1`.
""".
-spec match_expr(syntaxTree(), syntaxTree()) -> syntaxTree().

match_expr(Pattern, Body) ->
    tree(match_expr, #match_expr{pattern = Pattern, body = Body}).

revert_match_expr(Node) ->
    Pos = get_pos(Node),
    Pattern = match_expr_pattern(Node),
    Body = match_expr_body(Node),
    {match, Pos, Pattern, Body}.


%% =====================================================================
%% @doc Returns the pattern subtree of a `match_expr' node.
%%
%% @see match_expr/2

-doc """
Returns the pattern subtree of a `match_expr` node.

_See also: _`match_expr/2`.
""".
-spec match_expr_pattern(syntaxTree()) -> syntaxTree().

match_expr_pattern(Node) ->
    case unwrap(Node) of
	{match, _, Pattern, _} ->
	    Pattern;
	Node1 ->
	    (data(Node1))#match_expr.pattern
    end.


%% =====================================================================
%% @doc Returns the body subtree of a `match_expr' node.
%%
%% @see match_expr/2

-doc """
Returns the body subtree of a `match_expr` node.

_See also: _`match_expr/2`.
""".
-spec match_expr_body(syntaxTree()) -> syntaxTree().

match_expr_body(Node) ->
    case unwrap(Node) of
	{match, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#match_expr.body
    end.


%% =====================================================================
%% @doc Creates an abstract maybe-expression, as used in <code>maybe</code>
%% blocks. The result represents
%% "<code><em>Pattern</em> ?= <em>Body</em></code>".
%%
%% @see maybe_match_expr_pattern/1
%% @see maybe_match_expr_body/1
%% @see maybe_expr/2

-record(maybe_match_expr, {pattern :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = maybe_expr
%% data(Node) = #maybe_expr{pattern :: Pattern, body :: Body}
%%
%%	Pattern = Body = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {maybe_match, Pos, Pattern, Body}
%%
%%	Pattern = Body = erl_parse()
%%

-doc """
Creates an abstract maybe-expression, as used in `maybe` blocks. The result
represents "`*Pattern* ?= *Body*`".

_See also: _`maybe_expr/2`, `maybe_match_expr_body/1`,
`maybe_match_expr_pattern/1`.
""".
-spec maybe_match_expr(syntaxTree(), syntaxTree()) -> syntaxTree().

maybe_match_expr(Pattern, Body) ->
    tree(maybe_match_expr, #maybe_match_expr{pattern = Pattern, body = Body}).

revert_maybe_match_expr(Node) ->
    Pos = get_pos(Node),
    Pattern = maybe_match_expr_pattern(Node),
    Body = maybe_match_expr_body(Node),
    {maybe_match, Pos, Pattern, Body}.

%% =====================================================================
%% @doc Returns the pattern subtree of a `maybe_expr' node.
%%
%% @see maybe_match_expr/2

-doc """
Returns the pattern subtree of a `maybe_expr` node.

_See also: _`maybe_match_expr/2`.
""".
-spec maybe_match_expr_pattern(syntaxTree()) -> syntaxTree().

maybe_match_expr_pattern(Node) ->
    case unwrap(Node) of
        {maybe_match, _, Pattern, _} ->
            Pattern;
        Node1 ->
            (data(Node1))#maybe_match_expr.pattern
    end.


%% =====================================================================
%% @doc Returns the body subtree of a `maybe_expr' node.
%%
%% @see maybe_match_expr/2

-doc """
Returns the body subtree of a `maybe_expr` node.

_See also: _`maybe_match_expr/2`.
""".
-spec maybe_match_expr_body(syntaxTree()) -> syntaxTree().

maybe_match_expr_body(Node) ->
    case unwrap(Node) of
        {maybe_match, _, _, Body} ->
            Body;
        Node1 ->
            (data(Node1))#maybe_match_expr.body
    end.

%% =====================================================================
%% @doc Creates an abstract operator. The name of the operator is the
%% character sequence represented by `Name'. This is
%% analogous to the print name of an atom, but an operator is never
%% written within single-quotes; e.g., the result of
%% <code>operator('++')</code> represents "<code>++</code>" rather
%% than "<code>'++'</code>".
%%
%% @see operator_name/1
%% @see operator_literal/1
%% @see atom/1

%% type(Node) = operator
%% data(Node) = atom()

-doc """
Creates an abstract operator. The name of the operator is the character sequence
represented by `Name`. This is analogous to the print name of an atom, but an
operator is never written within single-quotes; e.g., the result of
[`operator('++')`](`operator/1`) represents "`++`" rather than "`'++'`".

_See also: _`atom/1`, `operator_literal/1`, `operator_name/1`.
""".
-spec operator(atom() | string()) -> syntaxTree().

operator(Name) when is_atom(Name) ->
    tree(operator, Name);
operator(Name) ->
    tree(operator, list_to_atom(Name)).


%% =====================================================================
%% @doc Returns the name of an `operator' node. Note that
%% the name is returned as an atom.
%%
%% @see operator/1

-doc """
Returns the name of an `operator` node. Note that the name is returned as an
atom.

_See also: _`operator/1`.
""".
-spec operator_name(syntaxTree()) -> atom().

operator_name(Node) ->
    data(Node).


%% =====================================================================
%% @doc Returns the literal string represented by an
%% `operator' node. This is simply the operator name as a string.
%%
%% @see operator/1

-doc """
Returns the literal string represented by an `operator` node. This is simply the
operator name as a string.

_See also: _`operator/1`.
""".
-spec operator_literal(syntaxTree()) -> string().

operator_literal(Node) ->
    atom_to_list(operator_name(Node)).


%% =====================================================================
%% @doc Creates an abstract infix operator expression. The result
%% represents "<code><em>Left</em> <em>Operator</em>
%% <em>Right</em></code>".
%%
%% @see infix_expr_left/1
%% @see infix_expr_right/1
%% @see infix_expr_operator/1
%% @see prefix_expr/2

-record(infix_expr, {operator :: syntaxTree(),
		     left     :: syntaxTree(),
		     right    :: syntaxTree()}).

%% type(Node) = infix_expr
%% data(Node) = #infix_expr{left :: Left, operator :: Operator,
%%		            right :: Right}
%%
%%	Left = Operator = Right = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {op, Pos, Operator, Left, Right}
%%
%%	Operator = atom()
%%	Left = Right = erl_parse()

-doc """
Creates an abstract infix operator expression. The result represents
"`*Left**Operator**Right*`".

_See also: _`infix_expr_left/1`, `infix_expr_operator/1`, `infix_expr_right/1`,
`prefix_expr/2`.
""".
-spec infix_expr(syntaxTree(), syntaxTree(), syntaxTree()) -> syntaxTree().

infix_expr(Left, Operator, Right) ->
    tree(infix_expr, #infix_expr{operator = Operator, left = Left,
				 right = Right}).

revert_infix_expr(Node) ->
    Pos = get_pos(Node),
    Operator = infix_expr_operator(Node),
    Left = infix_expr_left(Node),
    Right = infix_expr_right(Node),
    case type(Operator) of
	operator ->
	    %% Note that the operator itself is not revertible out
	    %% of context.
	    {op, Pos, operator_name(Operator), Left, Right};
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the left argument subtree of an
%% `infix_expr' node.
%%
%% @see infix_expr/3

-doc """
Returns the left argument subtree of an `infix_expr` node.

_See also: _`infix_expr/3`.
""".
-spec infix_expr_left(syntaxTree()) -> syntaxTree().

infix_expr_left(Node) ->
    case unwrap(Node) of
	{op, _, _, Left, _} ->
	    Left;
	Node1 ->
	    (data(Node1))#infix_expr.left
    end.


%% =====================================================================
%% @doc Returns the operator subtree of an `infix_expr' node.
%%
%% @see infix_expr/3

-doc """
Returns the operator subtree of an `infix_expr` node.

_See also: _`infix_expr/3`.
""".
-spec infix_expr_operator(syntaxTree()) -> syntaxTree().

infix_expr_operator(Node) ->
    case unwrap(Node) of
	{op, Pos, Operator, _, _} ->
	    set_pos(operator(Operator), Pos);
	Node1 ->
	    (data(Node1))#infix_expr.operator
    end.


%% =====================================================================
%% @doc Returns the right argument subtree of an
%% `infix_expr' node.
%%
%% @see infix_expr/3

-doc """
Returns the right argument subtree of an `infix_expr` node.

_See also: _`infix_expr/3`.
""".
-spec infix_expr_right(syntaxTree()) -> syntaxTree().

infix_expr_right(Node) ->
    case unwrap(Node) of
	{op, _, _, _, Right} ->
	    Right;
	Node1 ->
	    (data(Node1))#infix_expr.right
    end.


%% =====================================================================
%% @doc Creates an abstract prefix operator expression. The result
%% represents "<code><em>Operator</em> <em>Argument</em></code>".
%%
%% @see prefix_expr_argument/1
%% @see prefix_expr_operator/1
%% @see infix_expr/3

-record(prefix_expr, {operator :: syntaxTree(), argument :: syntaxTree()}).

%% type(Node) = prefix_expr
%% data(Node) = #prefix_expr{operator :: Operator,
%%		             argument :: Argument}
%%
%%	Operator = Argument = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {op, Pos, Operator, Arg}
%%
%%	Operator = atom()
%%	Argument = erl_parse()

-doc """
Creates an abstract prefix operator expression. The result represents
"`*Operator**Argument*`".

_See also: _`infix_expr/3`, `prefix_expr_argument/1`, `prefix_expr_operator/1`.
""".
-spec prefix_expr(syntaxTree(), syntaxTree()) -> syntaxTree().

prefix_expr(Operator, Argument) ->
    tree(prefix_expr, #prefix_expr{operator = Operator,
				   argument = Argument}).

revert_prefix_expr(Node) ->
    Pos = get_pos(Node),
    Operator = prefix_expr_operator(Node),
    Argument = prefix_expr_argument(Node),
    case type(Operator) of
	operator ->
	    %% Note that the operator itself is not revertible out
	    %% of context.
	    {op, Pos, operator_name(Operator), Argument};
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the operator subtree of a `prefix_expr' node.
%%
%% @see prefix_expr/2

-doc """
Returns the operator subtree of a `prefix_expr` node.

_See also: _`prefix_expr/2`.
""".
-spec prefix_expr_operator(syntaxTree()) -> syntaxTree().

prefix_expr_operator(Node) ->
    case unwrap(Node) of
	{op, Pos, Operator, _} ->
	    set_pos(operator(Operator), Pos);
	Node1 ->
	    (data(Node1))#prefix_expr.operator
    end.


%% =====================================================================
%% @doc Returns the argument subtree of a `prefix_expr' node.
%%
%% @see prefix_expr/2

-doc """
Returns the argument subtree of a `prefix_expr` node.

_See also: _`prefix_expr/2`.
""".
-spec prefix_expr_argument(syntaxTree()) -> syntaxTree().

prefix_expr_argument(Node) ->
    case unwrap(Node) of
	{op, _, _, Argument} ->
	    Argument;
	Node1 ->
	    (data(Node1))#prefix_expr.argument
    end.


%% =====================================================================
%% @equiv record_field(Name, none)

-doc "Equivalent to [record_field(Name, none)](`record_field/2`).".
-spec record_field(syntaxTree()) -> syntaxTree().

record_field(Name) ->
    record_field(Name, none).


%% =====================================================================
%% @doc Creates an abstract record field specification. If
%% `Value' is `none', the result represents
%% simply "<code><em>Name</em></code>", otherwise it represents
%% "<code><em>Name</em> = <em>Value</em></code>".
%%
%% @see record_field_name/1
%% @see record_field_value/1
%% @see record_expr/3

-record(record_field, {name :: syntaxTree(), value :: 'none' | syntaxTree()}).

%% type(Node) = record_field
%% data(Node) = #record_field{name :: Name, value :: Value}
%%
%%	Name = syntaxTree()
%%	Value = none | syntaxTree()

-doc """
Creates an abstract record field specification. If `Value` is `none`, the result
represents simply "`*Name*`", otherwise it represents "`*Name* = *Value*`".

_See also: _`record_expr/3`, `record_field_name/1`, `record_field_value/1`.
""".
-spec record_field(syntaxTree(), 'none' | syntaxTree()) -> syntaxTree().

record_field(Name, Value) ->
    tree(record_field, #record_field{name = Name, value = Value}).


%% =====================================================================
%% @doc Returns the name subtree of a `record_field' node.
%%
%% @see record_field/2

-doc """
Returns the name subtree of a `record_field` node.

_See also: _`record_field/2`.
""".
-spec record_field_name(syntaxTree()) -> syntaxTree().

record_field_name(Node) ->
    (data(Node))#record_field.name.


%% =====================================================================
%% @doc Returns the value subtree of a `record_field' node,
%% if any. If `Node' represents
%% "<code><em>Name</em></code>", `none' is
%% returned. Otherwise, if `Node' represents
%% "<code><em>Name</em> = <em>Value</em></code>", `Value'
%% is returned.
%%
%% @see record_field/2

-doc """
Returns the value subtree of a `record_field` node, if any. If `Node` represents
"`*Name*`", `none` is returned. Otherwise, if `Node` represents
"`*Name* = *Value*`", `Value` is returned.

_See also: _`record_field/2`.
""".
-spec record_field_value(syntaxTree()) -> 'none' | syntaxTree().

record_field_value(Node) ->
    (data(Node))#record_field.value.


%% =====================================================================
%% @doc Creates an abstract record field index expression. The result
%% represents "<code>#<em>Type</em>.<em>Field</em></code>".
%%
%% (Note: the function name `record_index/2' is reserved
%% by the Erlang compiler, which is why that name could not be used
%% for this constructor.)
%%
%% @see record_index_expr_type/1
%% @see record_index_expr_field/1
%% @see record_expr/3

-record(record_index_expr, {type :: syntaxTree(), field :: syntaxTree()}).

%% type(Node) = record_index_expr
%% data(Node) = #record_index_expr{type :: Type, field :: Field}
%%
%%	Type = Field = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {record_index, Pos, Type, Field}
%%
%%	Type = atom()
%%	Field = erl_parse()

-doc """
Creates an abstract record field index expression. The result represents
"`#*Type*.*Field*`".

(Note: the function name `record_index/2` is reserved by the Erlang compiler,
which is why that name could not be used for this constructor.)

_See also: _`record_expr/3`, `record_index_expr_field/1`,
`record_index_expr_type/1`.
""".
-spec record_index_expr(syntaxTree(), syntaxTree()) -> syntaxTree().

record_index_expr(Type, Field) ->
    tree(record_index_expr, #record_index_expr{type = Type,
					       field = Field}).

revert_record_index_expr(Node) ->
    Pos = get_pos(Node),
    Type = record_index_expr_type(Node),
    Field = record_index_expr_field(Node),
    case type(Type) of
	atom ->
	    {record_index, Pos, concrete(Type), Field};
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the type subtree of a `record_index_expr' node.
%%
%% @see record_index_expr/2

-doc """
Returns the type subtree of a `record_index_expr` node.

_See also: _`record_index_expr/2`.
""".
-spec record_index_expr_type(syntaxTree()) -> syntaxTree().

record_index_expr_type(Node) ->
    case unwrap(Node) of
	{record_index, Pos, Type, _} ->
	    set_pos(atom(Type), Pos);
	Node1 ->
	    (data(Node1))#record_index_expr.type
    end.


%% =====================================================================
%% @doc Returns the field subtree of a `record_index_expr' node.
%%
%% @see record_index_expr/2

-doc """
Returns the field subtree of a `record_index_expr` node.

_See also: _`record_index_expr/2`.
""".
-spec record_index_expr_field(syntaxTree()) -> syntaxTree().

record_index_expr_field(Node) ->
    case unwrap(Node) of
	{record_index, _, _, Field} ->
	    Field;
	Node1 ->
	    (data(Node1))#record_index_expr.field
    end.


%% =====================================================================
%% @doc Creates an abstract record field access expression. The result
%% represents "<code><em>Argument</em>#<em>Type</em>.<em>Field</em></code>".
%%
%% @see record_access_argument/1
%% @see record_access_type/1
%% @see record_access_field/1
%% @see record_expr/3

-record(record_access, {argument :: syntaxTree(),
			type     :: syntaxTree(),
			field    :: syntaxTree()}).

%% type(Node) = record_access
%% data(Node) = #record_access{argument :: Argument, type :: Type,
%%			       field :: Field}
%%
%%	Argument = Type = Field = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {record_field, Pos, Argument, Type, Field}
%%
%%	Argument = Field = erl_parse()
%%	Type = atom()

-doc """
Creates an abstract record field access expression. The result represents
"`*Argument*#*Type*.*Field*`".

_See also: _`record_access_argument/1`, `record_access_field/1`,
`record_access_type/1`, `record_expr/3`.
""".
-spec record_access(syntaxTree(), syntaxTree(), syntaxTree()) ->
        syntaxTree().

record_access(Argument, Type, Field) ->
    tree(record_access,#record_access{argument = Argument,
				      type = Type,
				      field = Field}).

revert_record_access(Node) ->
    Pos = get_pos(Node),
    Argument = record_access_argument(Node),
    Type = record_access_type(Node),
    Field = record_access_field(Node),
    case type(Type) of
        atom ->
            {record_field, Pos, Argument, concrete(Type), Field};
        _ ->
            Node
    end.


%% =====================================================================
%% @doc Returns the argument subtree of a `record_access' node.
%%
%% @see record_access/3

-doc """
Returns the argument subtree of a `record_access` node.

_See also: _`record_access/3`.
""".
-spec record_access_argument(syntaxTree()) -> syntaxTree().

record_access_argument(Node) ->
    case unwrap(Node) of
	{record_field, _, Argument, _, _} ->
	    Argument;
	Node1 ->
	    (data(Node1))#record_access.argument
    end.


%% =====================================================================
%% @doc Returns the type subtree of a `record_access' node.
%%
%% @see record_access/3

-doc """
Returns the type subtree of a `record_access` node.

_See also: _`record_access/3`.
""".
-spec record_access_type(syntaxTree()) -> syntaxTree().

record_access_type(Node) ->
    case unwrap(Node) of
	{record_field, Pos, _, Type, _} ->
	    set_pos(atom(Type), Pos);
	Node1 ->
	    (data(Node1))#record_access.type
    end.


%% =====================================================================
%% @doc Returns the field subtree of a `record_access' node.
%%
%% @see record_access/3

-doc """
Returns the field subtree of a `record_access` node.

_See also: _`record_access/3`.
""".
-spec record_access_field(syntaxTree()) -> syntaxTree().

record_access_field(Node) ->
    case unwrap(Node) of
	{record_field, _, _, _, Field} ->
	    Field;
	Node1 ->
	    (data(Node1))#record_access.field
    end.


%% =====================================================================
%% @equiv record_expr(none, Type, Fields)

-doc "Equivalent to [record_expr(none, Type, Fields)](`record_expr/3`).".
-spec record_expr(syntaxTree(), [syntaxTree()]) -> syntaxTree().

record_expr(Type, Fields) ->
    record_expr(none, Type, Fields).


%% =====================================================================
%% @doc Creates an abstract record expression. If `Fields' is
%% `[F1, ..., Fn]', then if `Argument' is
%% `none', the result represents
%% "<code>#<em>Type</em>{<em>F1</em>, ..., <em>Fn</em>}</code>",
%% otherwise it represents
%% "<code><em>Argument</em>#<em>Type</em>{<em>F1</em>, ...,
%% <em>Fn</em>}</code>".
%%
%% @see record_expr/2
%% @see record_expr_argument/1
%% @see record_expr_fields/1
%% @see record_expr_type/1
%% @see record_field/2
%% @see record_index_expr/2
%% @see record_access/3

-record(record_expr, {argument :: 'none' | syntaxTree(),
		      type     :: syntaxTree(),
		      fields   :: [syntaxTree()]}).

%% type(Node) = record_expr
%% data(Node) = #record_expr{argument :: Argument, type :: Type,
%%			     fields :: Fields}
%%
%%	Argument = none | syntaxTree()
%%	Type = syntaxTree
%%	Fields = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {record, Pos, Type, Fields}
%% {record, Pos, Argument, Type, Fields}
%%
%%	Argument = erl_parse()
%%	Type = atom()
%%	Fields = [Entry]
%%	Entry = {record_field, Pos, Field, Value}
%%	      | {record_field, Pos, Field}
%%	Field = Value = erl_parse()

-doc """
Creates an abstract record expression. If `Fields` is `[F1, ..., Fn]`, then if
`Argument` is `none`, the result represents "`#*Type*{*F1*, ..., *Fn*}`",
otherwise it represents "`*Argument*#*Type*{*F1*, ..., *Fn*}`".

_See also: _`record_access/3`, `record_expr/2`, `record_expr_argument/1`,
`record_expr_fields/1`, `record_expr_type/1`, `record_field/2`,
`record_index_expr/2`.
""".
-spec record_expr('none' | syntaxTree(), syntaxTree(), [syntaxTree()]) ->
        syntaxTree().

record_expr(Argument, Type, Fields) ->
    tree(record_expr, #record_expr{argument = Argument,
				   type = Type, fields = Fields}).

revert_record_expr(Node) ->
    Pos = get_pos(Node),
    Argument = record_expr_argument(Node),
    Type = record_expr_type(Node),
    Fields = record_expr_fields(Node),
    case type(Type) of
	atom ->
	    T = concrete(Type),
	    Fs = fold_record_fields(Fields),
	    case Argument of
		none ->
		    {record, Pos, T, Fs};
		_ ->
		    {record, Pos, Argument, T, Fs}
	    end;
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the argument subtree of a `record_expr' node,
%% if any. If `Node' represents
%% "<code>#<em>Type</em>{...}</code>", `none' is returned.
%% Otherwise, if `Node' represents
%% "<code><em>Argument</em>#<em>Type</em>{...}</code>",
%% `Argument' is returned.
%%
%% @see record_expr/3

-doc """
Returns the argument subtree of a `record_expr` node, if any. If `Node`
represents "`#*Type*{...}`", `none` is returned. Otherwise, if `Node` represents
"`*Argument*#*Type*{...}`", `Argument` is returned.

_See also: _`record_expr/3`.
""".
-spec record_expr_argument(syntaxTree()) -> 'none' | syntaxTree().

record_expr_argument(Node) ->
    case unwrap(Node) of
	{record, _, _, _} ->
	    none;
	{record, _, Argument, _, _} ->
	    Argument;
	Node1 ->
	    (data(Node1))#record_expr.argument
    end.


%% =====================================================================
%% @doc Returns the type subtree of a `record_expr' node.
%%
%% @see record_expr/3

-doc """
Returns the type subtree of a `record_expr` node.

_See also: _`record_expr/3`.
""".
-spec record_expr_type(syntaxTree()) -> syntaxTree().

record_expr_type(Node) ->
    case unwrap(Node) of
	{record, Pos, Type, _} ->
	    set_pos(atom(Type), Pos);
	{record, Pos, _, Type, _} ->
	    set_pos(atom(Type), Pos);
	Node1 ->
	    (data(Node1))#record_expr.type
    end.


%% =====================================================================
%% @doc Returns the list of field subtrees of a
%% `record_expr' node.
%%
%% @see record_expr/3

-doc """
Returns the list of field subtrees of a `record_expr` node.

_See also: _`record_expr/3`.
""".
-spec record_expr_fields(syntaxTree()) -> [syntaxTree()].

record_expr_fields(Node) ->
    case unwrap(Node) of
	{record, _, _, Fields} ->
	    unfold_record_fields(Fields);
	{record, _, _, _, Fields} ->
	    unfold_record_fields(Fields);
	Node1 ->
	    (data(Node1))#record_expr.fields
    end.


%% =====================================================================
%% @doc Creates an abstract function application expression. If
%% `Module' is `none', this is call is equivalent
%% to `application(Function, Arguments)', otherwise it is
%% equivalent to `application(module_qualifier(Module, Function),
%% Arguments)'.
%%
%% (This is a utility function.)
%%
%% @see application/2
%% @see module_qualifier/2

-doc """
Creates an abstract function application expression. If `Module` is `none`, this
is call is equivalent to [`application(Function, Arguments)`](`application/2`),
otherwise it is equivalent to
[`application(module_qualifier(Module, Function), Arguments)`](`application/2`).

(This is a utility function.)

_See also: _`application/2`, `module_qualifier/2`.
""".
-spec application('none' | syntaxTree(), syntaxTree(), [syntaxTree()]) ->
        syntaxTree().

application(none, Name, Arguments) ->
    application(Name, Arguments);
application(Module, Name, Arguments) ->
    application(module_qualifier(Module, Name), Arguments).


%% =====================================================================
%% @doc Creates an abstract function application expression. If
%% `Arguments' is `[A1, ..., An]', the result
%% represents "<code><em>Operator</em>(<em>A1</em>, ...,
%% <em>An</em>)</code>".
%%
%% @see application_operator/1
%% @see application_arguments/1
%% @see application/3

-record(application, {operator :: syntaxTree(), arguments :: [syntaxTree()]}).

%% type(Node) = application
%% data(Node) = #application{operator :: Operator,
%%			     arguments :: Arguments}
%%
%%	Operator = syntaxTree()
%%	Arguments = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {call, Pos, Operator, Args}
%%
%%	Operator = erl_parse()
%%	Arguments = [erl_parse()]

-doc """
Creates an abstract function application expression. If `Arguments` is
`[A1, ..., An]`, the result represents "`*Operator*(*A1*, ..., *An*)`".

_See also: _`application/3`, `application_arguments/1`,
`application_operator/1`.
""".
-spec application(syntaxTree(), [syntaxTree()]) -> syntaxTree().

application(Operator, Arguments) ->
    tree(application, #application{operator = Operator,
				   arguments = Arguments}).

revert_application(Node) ->
    Pos = get_pos(Node),
    Operator = application_operator(Node),
    Arguments = application_arguments(Node),
    {call, Pos, Operator, Arguments}.


%% =====================================================================
%% @doc Returns the operator subtree of an `application' node.
%%
%% Note: if `Node' represents
%% "<code><em>M</em>:<em>F</em>(...)</code>", then the result is the
%% subtree representing "<code><em>M</em>:<em>F</em></code>".
%%
%% @see application/2
%% @see module_qualifier/2

-doc """
Returns the operator subtree of an `application` node.

Note: if `Node` represents "`*M*:*F*(...)`", then the result is the subtree
representing "`*M*:*F*`".

_See also: _`application/2`, `module_qualifier/2`.
""".
-spec application_operator(syntaxTree()) -> syntaxTree().

application_operator(Node) ->
    case unwrap(Node) of
	{call, _, Operator, _} ->
	    Operator;
	Node1 ->
	    (data(Node1))#application.operator
    end.


%% =====================================================================
%% @doc Returns the list of argument subtrees of an
%% `application' node.
%%
%% @see application/2

-doc """
Returns the list of argument subtrees of an `application` node.

_See also: _`application/2`.
""".
-spec application_arguments(syntaxTree()) -> [syntaxTree()].

application_arguments(Node) ->
    case unwrap(Node) of
	{call, _, _, Arguments} ->
	    Arguments;
	Node1 ->
	    (data(Node1))#application.arguments
    end.

%% =====================================================================
%% @doc Creates an abstract annotated type expression. The result
%% represents "<code><em>Name</em> :: <em>Type</em></code>".
%%
%% @see annotated_type_name/1
%% @see annotated_type_body/1

-record(annotated_type, {name :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = annotated_type
%% data(Node) = #annotated_type{name :: Name,
%%                              body :: Type}
%%
%%      Name = syntaxTree()
%%      Type = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {ann_type, Pos, [Name, Type]}
%%
%%      Name = erl_parse()
%%      Type = erl_parse()

-doc """
Creates an abstract annotated type expression. The result represents
"`*Name* :: *Type*`".

_See also: _`annotated_type_body/1`, `annotated_type_name/1`.
""".
-spec annotated_type(syntaxTree(), syntaxTree()) -> syntaxTree().

annotated_type(Name, Type) ->
    tree(annotated_type, #annotated_type{name = Name, body = Type}).

revert_annotated_type(Node) ->
    Pos = get_pos(Node),
    Name = annotated_type_name(Node),
    Type = annotated_type_body(Node),
    {ann_type, Pos, [Name, Type]}.


%% =====================================================================
%% @doc Returns the name subtree of an `annotated_type' node.
%%
%% @see annotated_type/2

-doc """
Returns the name subtree of an `annotated_type` node.

_See also: _`annotated_type/2`.
""".
-spec annotated_type_name(syntaxTree()) -> syntaxTree().

annotated_type_name(Node) ->
    case unwrap(Node) of
        {ann_type, _, [Name, _]} ->
            Name;
        Node1 ->
            (data(Node1))#annotated_type.name
    end.


%% =====================================================================
%% @doc Returns the type subtrees of an `annotated_type' node.
%%
%% @see annotated_type/2

-doc """
Returns the type subtrees of an `annotated_type` node.

_See also: _`annotated_type/2`.
""".
-spec annotated_type_body(syntaxTree()) -> syntaxTree().

annotated_type_body(Node) ->
    case unwrap(Node) of
        {ann_type, _, [_, Type]} ->
            Type;
        Node1 ->
            (data(Node1))#annotated_type.body
    end.


%% =====================================================================
%% @doc Creates an abstract fun of any type. The result represents
%% "<code>fun()</code>".

%% type(Node) = fun_type
%%
%% `erl_parse' representation:
%%
%% {type, Pos, 'fun', []}

-doc """
Creates an abstract fun of any type. The result represents "`fun()`".
""".
-spec fun_type() -> syntaxTree().

fun_type() ->
    tree(fun_type).

revert_fun_type(Node) ->
    Pos = get_pos(Node),
    {type, Pos, 'fun', []}.


%% =====================================================================
%% @doc Creates an abstract type application expression. If
%% `Module' is `none', this is call is equivalent
%% to `type_application(TypeName, Arguments)', otherwise it is
%% equivalent to `type_application(module_qualifier(Module, TypeName),
%% Arguments)'.
%%
%% (This is a utility function.)
%%
%% @see type_application/2
%% @see module_qualifier/2

-doc """
Creates an abstract type application expression. If `Module` is `none`, this is
call is equivalent to
[`type_application(TypeName, Arguments)`](`type_application/2`), otherwise it is
equivalent to
[`type_application(module_qualifier(Module, TypeName), Arguments)`](`type_application/2`).

(This is a utility function.)

_See also: _`module_qualifier/2`, `type_application/2`.
""".
-spec type_application('none' | syntaxTree(), syntaxTree(), [syntaxTree()]) ->
        syntaxTree().

type_application(none, TypeName, Arguments) ->
    type_application(TypeName, Arguments);
type_application(Module, TypeName, Arguments) ->
    type_application(module_qualifier(Module, TypeName), Arguments).


%% =====================================================================
%% @doc Creates an abstract type application expression. If `Arguments' is
%% `[T1, ..., Tn]', the result represents
%% "<code><em>TypeName</em>(<em>T1</em>, ...<em>Tn</em>)</code>".
%%
%% @see user_type_application/2
%% @see type_application/3
%% @see type_application_name/1
%% @see type_application_arguments/1

-record(type_application, {type_name :: syntaxTree(),
                           arguments :: [syntaxTree()]}).

%% type(Node) = type_application
%% data(Node) = #type_application{type_name :: TypeName,
%%                                arguments :: Arguments}
%%
%%      TypeName = syntaxTree()
%%      Arguments = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {remote, Pos, [Module, Name, Arguments]} |
%% {type, Pos, Name, Arguments}
%%
%%      Module = erl_parse()
%%      Name = atom()
%%      Arguments = [erl_parse()]

-doc """
Creates an abstract type application expression. If `Arguments` is
`[T1, ..., Tn]`, the result represents "`*TypeName*(*T1*, ...*Tn*)`".

_See also: _`type_application/3`, `type_application_arguments/1`,
`type_application_name/1`, `user_type_application/2`.
""".
-spec type_application(syntaxTree(), [syntaxTree()]) -> syntaxTree().

type_application(TypeName, Arguments) ->
    tree(type_application,
         #type_application{type_name = TypeName, arguments = Arguments}).

revert_type_application(Node) ->
    Pos = get_pos(Node),
    TypeName = type_application_name(Node),
    Arguments = type_application_arguments(Node),
    case type(TypeName) of
        module_qualifier ->
            Module = module_qualifier_argument(TypeName),
            Name = module_qualifier_body(TypeName),
            {remote_type, Pos, [Module, Name, Arguments]};
        atom ->
            {type, Pos, atom_value(TypeName), Arguments}
    end.


%% =====================================================================
%% @doc Returns the type name subtree of a `type_application' node.
%%
%% @see type_application/2

-doc """
Returns the type name subtree of a `type_application` node.

_See also: _`type_application/2`.
""".
-spec type_application_name(syntaxTree()) -> syntaxTree().

type_application_name(Node) ->
    case unwrap(Node) of
        {remote_type, _, [Module, Name, _]} ->
            module_qualifier(Module, Name);
        {type, Pos, Name, _} ->
            set_pos(atom(Name), Pos);
        Node1 ->
            (data(Node1))#type_application.type_name
    end.


%% =====================================================================
%% @doc Returns the arguments subtrees of a `type_application' node.
%%
%% @see type_application/2

-doc """
Returns the arguments subtrees of a `type_application` node.

_See also: _`type_application/2`.
""".
-spec type_application_arguments(syntaxTree()) -> [syntaxTree()].

type_application_arguments(Node) ->
    case unwrap(Node) of
        {remote_type, _, [_, _, Arguments]} ->
            Arguments;
        {type, _, _, Arguments} ->
            Arguments;
        Node1 ->
            (data(Node1))#type_application.arguments
    end.


%% =====================================================================
%% @doc Creates an abstract bitstring type. The result represents
%% "<code><em>&lt;&lt;_:M, _:_*N&gt;&gt;</em></code>".
%%
%% @see bitstring_type_m/1
%% @see bitstring_type_n/1

-record(bitstring_type, {m :: syntaxTree(), n :: syntaxTree()}).

%% type(Node) = bitstring_type
%% data(Node) = #bitstring_type{m :: M, n :: N}
%%
%%      M = syntaxTree()
%%      N = syntaxTree()
%%

-doc """
Creates an abstract bitstring type. The result represents "`*<<_:M, _:_*N>>*`".

_See also: _`bitstring_type_m/1`, `bitstring_type_n/1`.
""".
-spec bitstring_type(syntaxTree(), syntaxTree()) -> syntaxTree().

bitstring_type(M, N) ->
    tree(bitstring_type, #bitstring_type{m = M, n =N}).

revert_bitstring_type(Node) ->
    Pos = get_pos(Node),
    M = bitstring_type_m(Node),
    N = bitstring_type_n(Node),
    {type, Pos, binary, [M, N]}.

%% =====================================================================
%% @doc Returns the number of start bits, `M',  of a `bitstring_type' node.
%%
%% @see bitstring_type/2

-doc """
Returns the number of start bits, `M`, of a `bitstring_type` node.

_See also: _`bitstring_type/2`.
""".
-spec bitstring_type_m(syntaxTree()) -> syntaxTree().

bitstring_type_m(Node) ->
    case unwrap(Node) of
        {type, _, binary, [M, _]} ->
            M;
        Node1 ->
            (data(Node1))#bitstring_type.m
    end.

%% =====================================================================
%% @doc Returns the segment size, `N', of a `bitstring_type' node.
%%
%% @see bitstring_type/2

-doc """
Returns the segment size, `N`, of a `bitstring_type` node.

_See also: _`bitstring_type/2`.
""".
-spec bitstring_type_n(syntaxTree()) -> syntaxTree().

bitstring_type_n(Node) ->
    case unwrap(Node) of
        {type, _, binary, [_, N]} ->
            N;
        Node1 ->
            (data(Node1))#bitstring_type.n
    end.


%% =====================================================================
%% @doc Creates an abstract constrained function type.
%% If `FunctionConstraint' is `[C1, ..., Cn]', the result represents
%% "<code><em>FunctionType</em> when <em>C1</em>, ...<em>Cn</em></code>".
%%
%% @see constrained_function_type_body/1
%% @see constrained_function_type_argument/1

-record(constrained_function_type, {body :: syntaxTree(),
                                    argument :: syntaxTree()}).

%% type(Node) = constrained_function_type
%% data(Node) = #constrained_function_type{body :: FunctionType,
%%                                         argument :: FunctionConstraint}
%%
%%      FunctionType = syntaxTree()
%%      FunctionConstraint = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {type, Pos, bounded_fun, [FunctionType, FunctionConstraint]}
%%
%%      FunctionType = erl_parse()
%%      FunctionConstraint = [erl_parse()]

-doc """
Creates an abstract constrained function type. If `FunctionConstraint` is
`[C1, ..., Cn]`, the result represents "`*FunctionType* when *C1*, ...*Cn*`".

_See also: _`constrained_function_type_argument/1`,
`constrained_function_type_body/1`.
""".
-spec constrained_function_type(syntaxTree(), [syntaxTree()]) -> syntaxTree().

constrained_function_type(FunctionType, FunctionConstraint) ->
    Conj = conjunction(FunctionConstraint),
    tree(constrained_function_type,
         #constrained_function_type{body = FunctionType,
                                    argument = Conj}).

revert_constrained_function_type(Node) ->
    Pos = get_pos(Node),
    FunctionType = constrained_function_type_body(Node),
    FunctionConstraint =
        conjunction_body(constrained_function_type_argument(Node)),
    {type, Pos, bounded_fun, [FunctionType, FunctionConstraint]}.


%% =====================================================================
%% @doc Returns the function type subtree of a
%% `constrained_function_type' node.
%%
%% @see constrained_function_type/2

-doc """
Returns the function type subtree of a `constrained_function_type` node.

_See also: _`constrained_function_type/2`.
""".
-spec constrained_function_type_body(syntaxTree()) -> syntaxTree().

constrained_function_type_body(Node) ->
    case unwrap(Node) of
        {type, _, bounded_fun, [FunctionType, _]} ->
            FunctionType;
        Node1 ->
            (data(Node1))#constrained_function_type.body
    end.

%% =====================================================================
%% @doc Returns the function constraint subtree of a
%% `constrained_function_type' node.
%%
%% @see constrained_function_type/2

-doc """
Returns the function constraint subtree of a `constrained_function_type` node.

_See also: _`constrained_function_type/2`.
""".
-spec constrained_function_type_argument(syntaxTree()) -> syntaxTree().

constrained_function_type_argument(Node) ->
    case unwrap(Node) of
        {type, _, bounded_fun, [_, FunctionConstraint]} ->
            conjunction(FunctionConstraint);
        Node1 ->
            (data(Node1))#constrained_function_type.argument
    end.


%% =====================================================================
%% @equiv function_type(any_arity, Type)

-doc "Equivalent to [function_type(any_arity, Type)](`function_type/2`).".
-spec function_type(syntaxTree()) -> syntaxTree().

function_type(Type) ->
    function_type(any_arity, Type).

%% =====================================================================
%% @doc Creates an abstract function type. If `Arguments' is
%% `[T1, ..., Tn]', then if it occurs within a function
%% specification, the result represents
%% "<code>(<em>T1</em>, ...<em>Tn</em>) -> <em>Return</em></code>"; otherwise
%% it represents
%% "<code>fun((<em>T1</em>, ...<em>Tn</em>) -> <em>Return</em>)</code>".
%% If `Arguments' is `any_arity', it represents
%% "<code>fun((...) -> <em>Return</em>)</code>".
%%
%% Note that the `erl_parse' representation is identical for
%% "<code><em>FunctionType</em></code>" and
%% "<code>fun(<em>FunctionType</em>)</code>".
%%
%% @see function_type_arguments/1
%% @see function_type_return/1

-record(function_type, {arguments :: any_arity | [syntaxTree()],
                        return :: syntaxTree()}).

%% type(Node) = function_type
%% data(Node) = #function_type{arguments :: any | Arguments,
%%                             return :: Type}
%%
%%      Arguments = [syntaxTree()]
%%      Type = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {type, Pos, 'fun', [{type, Pos, product, Arguments}, Type]}
%% {type, Pos, 'fun', [{type, Pos, any}, Type]}
%%
%%      Arguments = [erl_parse()]
%%      Type = erl_parse()

-doc """
Creates an abstract function type. If `Arguments` is `[T1, ..., Tn]`, then if it
occurs within a function specification, the result represents
"`(*T1*, ...*Tn*) -> *Return*`"; otherwise it represents
"`fun((*T1*, ...*Tn*) -> *Return*)`". If `Arguments` is `any_arity`, it
represents "`fun((...) -> *Return*)`".

Note that the `erl_parse` representation is identical for "`*FunctionType*`" and
"`fun(*FunctionType*)`".

_See also: _`function_type_arguments/1`, `function_type_return/1`.
""".
-spec function_type('any_arity' | [syntaxTree()], syntaxTree()) -> syntaxTree().

function_type(Arguments, Return) ->
    tree(function_type,
         #function_type{arguments = Arguments, return = Return}).

revert_function_type(Node) ->
    Pos = get_pos(Node),
    Type = function_type_return(Node),
    case function_type_arguments(Node) of
        any_arity ->
            {type, Pos, 'fun', [{type, Pos, any}, Type]};
        Arguments ->
            {type, Pos, 'fun', [{type, Pos, product, Arguments}, Type]}
    end.


%% =====================================================================
%% @doc Returns the argument types subtrees of a `function_type' node.
%% If `Node' represents "<code>fun((...) -> <em>Return</em>)</code>",
%% `any_arity' is returned; otherwise, if `Node' represents
%% "<code>(<em>T1</em>, ...<em>Tn</em>) -> <em>Return</em></code>" or
%% "<code>fun((<em>T1</em>, ...<em>Tn</em>) -> <em>Return</em>)</code>",
%% `[T1, ..., Tn]' is returned.

%%
%% @see function_type/1
%% @see function_type/2

-doc """
Returns the argument types subtrees of a `function_type` node. If `Node`
represents "`fun((...) -> *Return*)`", `any_arity` is returned; otherwise, if
`Node` represents "`(*T1*, ...*Tn*) -> *Return*`" or
"`fun((*T1*, ...*Tn*) -> *Return*)`", `[T1, ..., Tn]` is returned.

_See also: _`function_type/1`, `function_type/2`.
""".
-spec function_type_arguments(syntaxTree()) -> any_arity | [syntaxTree()].

function_type_arguments(Node) ->
    case unwrap(Node) of
        {type, _, 'fun', [{type, _, any}, _]} ->
            any_arity;
        {type, _, 'fun', [{type, _, product, Arguments}, _]} ->
            Arguments;
        Node1 ->
            (data(Node1))#function_type.arguments
    end.

%% =====================================================================
%% @doc Returns the return type subtrees of a `function_type' node.
%%
%% @see function_type/1
%% @see function_type/2

-doc """
Returns the return type subtrees of a `function_type` node.

_See also: _`function_type/1`, `function_type/2`.
""".
-spec function_type_return(syntaxTree()) -> syntaxTree().

function_type_return(Node) ->
    case unwrap(Node) of
        {type, _, 'fun', [_, Type]} ->
            Type;
        Node1 ->
            (data(Node1))#function_type.return
    end.


%% =====================================================================
%% @doc Creates an abstract (subtype) constraint. The result represents
%% "<code><em>Name</em> :: <em>Type</em></code>".
%%
%% @see constraint_argument/1
%% @see constraint_body/1

-record(constraint, {name :: syntaxTree(),
                     types :: [syntaxTree()]}).

%% type(Node) = constraint
%% data(Node) = #constraint{name :: Name,
%%                          types :: [Type]}
%%
%%      Name = syntaxTree()
%%      Type = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {type, Pos, constraint, [Name, [Var, Type]]}
%%
%%      Name = {atom, Pos, is_subtype}
%%      Var = erl_parse()
%%      Type = erl_parse()

-doc """
Creates an abstract (subtype) constraint. The result represents
"`*Name* :: *Type*`".

_See also: _`constraint_argument/1`, `constraint_body/1`.
""".
-spec constraint(syntaxTree(), [syntaxTree()]) -> syntaxTree().

constraint(Name, Types) ->
    tree(constraint,
         #constraint{name = Name, types = Types}).

revert_constraint(Node) ->
    Pos = get_pos(Node),
    Name = constraint_argument(Node),
    Types = constraint_body(Node),
    {type, Pos, constraint, [Name, Types]}.


%% =====================================================================
%% @doc Returns the name subtree of a `constraint' node.
%%
%% @see constraint/2

-doc """
Returns the name subtree of a `constraint` node.

_See also: _`constraint/2`.
""".
-spec constraint_argument(syntaxTree()) -> syntaxTree().

constraint_argument(Node) ->
    case unwrap(Node) of
        {type, _, constraint, [Name, _]} ->
            Name;
        Node1 ->
            (data(Node1))#constraint.name
    end.

%% =====================================================================
%% @doc Returns the type subtree of a `constraint' node.
%%
%% @see constraint/2

-doc """
Returns the type subtree of a `constraint` node.

_See also: _`constraint/2`.
""".
-spec constraint_body(syntaxTree()) -> [syntaxTree()].

constraint_body(Node) ->
    case unwrap(Node) of
        {type, _, constraint, [_, Types]} ->
            Types;
        Node1 ->
            (data(Node1))#constraint.types
    end.


%% =====================================================================
%% @doc Creates an abstract map type assoc field. The result represents
%% "<code><em>Name</em> => <em>Value</em></code>".
%%
%% @see map_type_assoc_name/1
%% @see map_type_assoc_value/1
%% @see map_type/1

-record(map_type_assoc, {name :: syntaxTree(), value :: syntaxTree()}).

%% `erl_parse' representation:
%%
%% {type, Pos, map_field_assoc, [Name, Value]}

-doc """
Creates an abstract map type assoc field. The result represents
"`*Name* => *Value*`".

_See also: _`map_type/1`, `map_type_assoc_name/1`, `map_type_assoc_value/1`.
""".
-spec map_type_assoc(syntaxTree(), syntaxTree()) -> syntaxTree().

map_type_assoc(Name, Value) ->
    tree(map_type_assoc, #map_type_assoc{name = Name, value = Value}).

revert_map_type_assoc(Node) ->
    Pos = get_pos(Node),
    Name = map_type_assoc_name(Node),
    Value = map_type_assoc_value(Node),
    {type, Pos, map_field_assoc, [Name, Value]}.


%% =====================================================================
%% @doc Returns the name subtree of a `map_type_assoc' node.
%%
%% @see map_type_assoc/2

-doc """
Returns the name subtree of a `map_type_assoc` node.

_See also: _`map_type_assoc/2`.
""".
-spec map_type_assoc_name(syntaxTree()) -> syntaxTree().

map_type_assoc_name(Node) ->
    case unwrap(Node) of
        {type, _, map_field_assoc, [Name, _]} ->
            Name;
        Node1 ->
            (data(Node1))#map_type_assoc.name
    end.


%% =====================================================================
%% @doc Returns the value subtree of a `map_type_assoc' node.
%%
%% @see map_type_assoc/2

-doc """
Returns the value subtree of a `map_type_assoc` node.

_See also: _`map_type_assoc/2`.
""".
-spec map_type_assoc_value(syntaxTree()) -> syntaxTree().

map_type_assoc_value(Node) ->
    case unwrap(Node) of
        {type, _, map_field_assoc, [_, Value]} ->
            Value;
        Node1 ->
            (data(Node1))#map_type_assoc.value
    end.


%% =====================================================================
%% @doc Creates an abstract map type exact field. The result represents
%% "<code><em>Name</em> := <em>Value</em></code>".
%%
%% @see map_type_exact_name/1
%% @see map_type_exact_value/1
%% @see map_type/1

-record(map_type_exact, {name :: syntaxTree(), value :: syntaxTree()}).

%% `erl_parse' representation:
%%
%% {type, Pos, map_field_exact, [Name, Value]}

-doc """
Creates an abstract map type exact field. The result represents
"`*Name* := *Value*`".

_See also: _`map_type/1`, `map_type_exact_name/1`, `map_type_exact_value/1`.
""".
-spec map_type_exact(syntaxTree(), syntaxTree()) -> syntaxTree().

map_type_exact(Name, Value) ->
    tree(map_type_exact, #map_type_exact{name = Name, value = Value}).

revert_map_type_exact(Node) ->
    Pos = get_pos(Node),
    Name = map_type_exact_name(Node),
    Value = map_type_exact_value(Node),
    {type, Pos, map_field_exact, [Name, Value]}.


%% =====================================================================
%% @doc Returns the name subtree of a `map_type_exact' node.
%%
%% @see map_type_exact/2

-doc """
Returns the name subtree of a `map_type_exact` node.

_See also: _`map_type_exact/2`.
""".
-spec map_type_exact_name(syntaxTree()) -> syntaxTree().

map_type_exact_name(Node) ->
    case unwrap(Node) of
        {type, _, map_field_exact, [Name, _]} ->
            Name;
        Node1 ->
            (data(Node1))#map_type_exact.name
    end.


%% =====================================================================
%% @doc Returns the value subtree of a `map_type_exact' node.
%%
%% @see map_type_exact/2

-doc """
Returns the value subtree of a `map_type_exact` node.

_See also: _`map_type_exact/2`.
""".
-spec map_type_exact_value(syntaxTree()) -> syntaxTree().

map_type_exact_value(Node) ->
    case unwrap(Node) of
        {type, _, map_field_exact, [_, Value]} ->
            Value;
        Node1 ->
            (data(Node1))#map_type_exact.value
    end.


%% =====================================================================
%% @equiv map_type(any_size)

-doc "Equivalent to [map_type(any_size)](`map_type/1`).".
-spec map_type() -> syntaxTree().

map_type() ->
    map_type(any_size).

%% =====================================================================
%% @doc Creates an abstract type map. If `Fields' is
%% `[F1, ..., Fn]', the result represents
%% "<code>#{<em>F1</em>, ..., <em>Fn</em>}</code>";
%% otherwise, if `Fields' is `any_size', it represents
%% "<code>map()</code>".
%%
%% @see map_type_fields/1

%% type(Node) = map_type
%% data(Node) = Fields
%%
%%      Fields = any_size | [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {type, Pos, map, [Field]}
%% {type, Pos, map, any}
%%
%%      Field = erl_parse()

-doc """
Creates an abstract type map. If `Fields` is `[F1, ..., Fn]`, the result
represents "`#{*F1*, ..., *Fn*}`"; otherwise, if `Fields` is `any_size`, it
represents "`t:map/0`".

_See also: _`map_type_fields/1`.
""".
-spec map_type('any_size' | [syntaxTree()]) -> syntaxTree().

map_type(Fields) ->
    tree(map_type, Fields).

revert_map_type(Node) ->
    Pos = get_pos(Node),
    case map_type_fields(Node) of
        any_size ->
            {type, Pos, map, any};
        Fields ->
            {type, Pos, map, Fields}
    end.

%% =====================================================================
%% @doc Returns the list of field subtrees of a `map_type' node.
%% If `Node' represents "<code>map()</code>", `any_size' is returned;
%% otherwise, if `Node' represents
%% "<code>#{<em>F1</em>, ..., <em>Fn</em>}</code>",
%% `[F1, ..., Fn]' is returned.
%%
%% @see map_type/0
%% @see map_type/1

-doc """
Returns the list of field subtrees of a `map_type` node. If `Node` represents
"`t:map/0`", `any_size` is returned; otherwise, if `Node` represents
"`#{*F1*, ..., *Fn*}`", `[F1, ..., Fn]` is returned.

_See also: _`map_type/0`, `map_type/1`.
""".
-spec map_type_fields(syntaxTree()) -> 'any_size' | [syntaxTree()].

map_type_fields(Node) ->
    case unwrap(Node) of
        {type, _, map, Fields} when is_list(Fields) ->
            Fields;
        {type, _, map, any} ->
            any_size;
        Node1 ->
            data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract range type. The result represents
%% "<code><em>Low</em> .. <em>High</em></code>".
%%
%% @see integer_range_type_low/1
%% @see integer_range_type_high/1

-record(integer_range_type, {low :: syntaxTree(),
                             high :: syntaxTree()}).

%% type(Node) = integer_range_type
%% data(Node) = #integer_range_type{low :: Low, high :: High}
%%
%%      Low = syntaxTree()
%%      High = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {type, Pos, range, [Low, High]}
%%
%%      Low = erl_parse()
%%      High = erl_parse()

-doc """
Creates an abstract range type. The result represents "`*Low* .. *High*`".

_See also: _`integer_range_type_high/1`, `integer_range_type_low/1`.
""".
-spec integer_range_type(syntaxTree(), syntaxTree()) -> syntaxTree().

integer_range_type(Low, High) ->
    tree(integer_range_type, #integer_range_type{low = Low, high = High}).

revert_integer_range_type(Node) ->
    Pos = get_pos(Node),
    Low = integer_range_type_low(Node),
    High = integer_range_type_high(Node),
    {type, Pos, range, [Low, High]}.


%% =====================================================================
%% @doc Returns the low limit of an `integer_range_type' node.
%%
%% @see integer_range_type/2

-doc """
Returns the low limit of an `integer_range_type` node.

_See also: _`integer_range_type/2`.
""".
-spec integer_range_type_low(syntaxTree()) -> syntaxTree().

integer_range_type_low(Node) ->
    case unwrap(Node) of
        {type, _, range, [Low, _]} ->
            Low;
        Node1 ->
            (data(Node1))#integer_range_type.low
    end.

%% =====================================================================
%% @doc Returns the high limit of an `integer_range_type' node.
%%
%% @see integer_range_type/2

-doc """
Returns the high limit of an `integer_range_type` node.

_See also: _`integer_range_type/2`.
""".
-spec integer_range_type_high(syntaxTree()) -> syntaxTree().

integer_range_type_high(Node) ->
    case unwrap(Node) of
        {type, _, range, [_, High]} ->
            High;
        Node1 ->
            (data(Node1))#integer_range_type.high
    end.


%% =====================================================================
%% @doc Creates an abstract record type. If `Fields' is
%% `[F1, ..., Fn]', the result represents
%% "<code>#<em>Name</em>{<em>F1</em>, ..., <em>Fn</em>}</code>".
%%
%% @see record_type_name/1
%% @see record_type_fields/1

-record(record_type, {name :: syntaxTree(),
                      fields :: [syntaxTree()]}).

%% type(Node) = record_type
%% data(Node) = #record_type{name = Name, fields = Fields}
%%
%%      Name = syntaxTree()
%%      Fields = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {type, Pos, record, [Name|Fields]}
%%
%%      Name = erl_parse()
%%      Fields = [erl_parse()]

-doc """
Creates an abstract record type. If `Fields` is `[F1, ..., Fn]`, the result
represents "`#*Name*{*F1*, ..., *Fn*}`".

_See also: _`record_type_fields/1`, `record_type_name/1`.
""".
-spec record_type(syntaxTree(), [syntaxTree()]) -> syntaxTree().

record_type(Name, Fields) ->
    tree(record_type, #record_type{name = Name, fields = Fields}).

revert_record_type(Node) ->
    Pos = get_pos(Node),
    Name = record_type_name(Node),
    Fields = record_type_fields(Node),
    {type, Pos, record, [Name | Fields]}.


%% =====================================================================
%% @doc Returns the name subtree of a `record_type' node.
%%
%% @see record_type/2

-doc """
Returns the name subtree of a `record_type` node.

_See also: _`record_type/2`.
""".
-spec record_type_name(syntaxTree()) -> syntaxTree().

record_type_name(Node) ->
    case unwrap(Node) of
        {type, _, record, [Name|_]} ->
            Name;
        Node1 ->
            (data(Node1))#record_type.name
    end.

%% =====================================================================
%% @doc Returns the fields subtree of a `record_type' node.
%%
%% @see record_type/2

-doc """
Returns the fields subtree of a `record_type` node.

_See also: _`record_type/2`.
""".
-spec record_type_fields(syntaxTree()) -> [syntaxTree()].

record_type_fields(Node) ->
    case unwrap(Node) of
        {type, _, record, [_|Fields]} ->
            Fields;
        Node1 ->
            (data(Node1))#record_type.fields
    end.


%% =====================================================================
%% @doc Creates an abstract record type field. The result represents
%% "<code><em>Name</em> :: <em>Type</em></code>".
%%
%% @see record_type_field_name/1
%% @see record_type_field_type/1

-record(record_type_field, {name :: syntaxTree(),
                            type :: syntaxTree()}).

%% type(Node) = record_type_field
%% data(Node) = #record_type_field{name = Name, type = Type}
%%
%%      Name = syntaxTree()
%%      Type = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {type, Pos, field_type, [Name, Type]}
%%
%%      Name = erl_parse()
%%      Type = erl_parse()

-doc """
Creates an abstract record type field. The result represents
"`*Name* :: *Type*`".

_See also: _`record_type_field_name/1`, `record_type_field_type/1`.
""".
-spec record_type_field(syntaxTree(), syntaxTree()) -> syntaxTree().

record_type_field(Name, Type) ->
    tree(record_type_field, #record_type_field{name = Name, type = Type}).

revert_record_type_field(Node) ->
    Pos = get_pos(Node),
    Name = record_type_field_name(Node),
    Type = record_type_field_type(Node),
    {type, Pos, field_type, [Name, Type]}.


%% =====================================================================
%% @doc Returns the name subtree of a `record_type_field' node.
%%
%% @see record_type_field/2

-doc """
Returns the name subtree of a `record_type_field` node.

_See also: _`record_type_field/2`.
""".
-spec record_type_field_name(syntaxTree()) -> syntaxTree().

record_type_field_name(Node) ->
    case unwrap(Node) of
        {type, _, field_type, [Name, _]} ->
            Name;
        Node1 ->
            (data(Node1))#record_type_field.name
    end.

%% =====================================================================
%% @doc Returns the type subtree of a `record_type_field' node.
%%
%% @see record_type_field/2

-doc """
Returns the type subtree of a `record_type_field` node.

_See also: _`record_type_field/2`.
""".
-spec record_type_field_type(syntaxTree()) -> syntaxTree().

record_type_field_type(Node) ->
    case unwrap(Node) of
        {type, _, field_type, [_, Type]} ->
            Type;
        Node1 ->
            (data(Node1))#record_type_field.type
    end.


%% =====================================================================
%% @equiv tuple_type(any_size)

-doc "Equivalent to [tuple_type(any_size)](`tuple_type/1`).".
-spec tuple_type() -> syntaxTree().

tuple_type() ->
    tuple_type(any_size).

%% =====================================================================
%% @doc Creates an abstract type tuple. If `Elements' is
%% `[T1, ..., Tn]', the result represents
%% "<code>{<em>T1</em>, ..., <em>Tn</em>}</code>";
%% otherwise, if `Elements' is `any_size', it represents
%% "<code>tuple()</code>".
%%
%% @see tuple_type_elements/1

%% type(Node) = tuple_type
%% data(Node) = Elements
%%
%%      Elements = any_size | [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {type, Pos, tuple, [Element]}
%% {type, Pos, tuple, any}
%%
%%      Element = erl_parse()

-doc """
Creates an abstract type tuple. If `Elements` is `[T1, ..., Tn]`, the result
represents "`{*T1*, ..., *Tn*}`"; otherwise, if `Elements` is `any_size`, it
represents "`t:tuple/0`".

_See also: _`tuple_type_elements/1`.
""".
-spec tuple_type(any_size | [syntaxTree()]) -> syntaxTree().

tuple_type(Elements) ->
    tree(tuple_type, Elements).

revert_tuple_type(Node) ->
    Pos = get_pos(Node),
    case tuple_type_elements(Node) of
        any_size ->
            {type, Pos, tuple, any};
        TypeElements ->
            {type, Pos, tuple, TypeElements}
    end.


%% =====================================================================
%% @doc Returns the list of type element subtrees of a `tuple_type' node.
%% If `Node' represents "<code>tuple()</code>", `any_size' is returned;
%% otherwise, if `Node' represents
%% "<code>{<em>T1</em>, ..., <em>Tn</em>}</code>",
%% `[T1, ..., Tn]' is returned.
%%
%% @see tuple_type/0
%% @see tuple_type/1

-doc """
Returns the list of type element subtrees of a `tuple_type` node. If `Node`
represents "`t:tuple/0`", `any_size` is returned; otherwise, if `Node`
represents "`{*T1*, ..., *Tn*}`", `[T1, ..., Tn]` is returned.

_See also: _`tuple_type/0`, `tuple_type/1`.
""".
-spec tuple_type_elements(syntaxTree()) -> 'any_size' | [syntaxTree()].

tuple_type_elements(Node) ->
    case unwrap(Node) of
        {type, _, tuple, Elements} when is_list(Elements) ->
            Elements;
        {type, _, tuple, any} ->
            any_size;
        Node1 ->
            data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract type union. If `Types' is
%% `[T1, ..., Tn]', the result represents
%% "<code><em>T1</em> | ... | <em>Tn</em></code>".
%%
%% @see type_union_types/1

%% type(Node) = type_union
%% data(Node) = Types
%%
%%      Types = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {type, Pos, union, Elements}
%%
%%      Elements = [erl_parse()]

-doc """
Creates an abstract type union. If `Types` is `[T1, ..., Tn]`, the result
represents "`*T1* | ... | *Tn*`".

_See also: _`type_union_types/1`.
""".
-spec type_union([syntaxTree()]) -> syntaxTree().

type_union(Types) ->
    tree(type_union, Types).

revert_type_union(Node) ->
    Pos = get_pos(Node),
    {type, Pos, union, type_union_types(Node)}.


%% =====================================================================
%% @doc Returns the list of type subtrees of a `type_union' node.
%%
%% @see type_union/1

-doc """
Returns the list of type subtrees of a `type_union` node.

_See also: _`type_union/1`.
""".
-spec type_union_types(syntaxTree()) -> [syntaxTree()].

type_union_types(Node) ->
    case unwrap(Node) of
        {type, _, union, Types} when is_list(Types) ->
            Types;
        Node1 ->
            data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract user type. If `Arguments' is
%% `[T1, ..., Tn]', the result represents
%% "<code><em>TypeName</em>(<em>T1</em>, ...<em>Tn</em>)</code>".
%%
%% @see type_application/2
%% @see user_type_application_name/1
%% @see user_type_application_arguments/1

-record(user_type_application, {type_name :: syntaxTree(),
                                arguments :: [syntaxTree()]}).

%% type(Node) = user_type_application
%% data(Node) = #user_type_application{type_name :: TypeName,
%%                                     arguments :: Arguments}
%%
%%      TypeName = syntaxTree()
%%      Arguments = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {user_type, Pos, Name, Arguments}
%%
%%      Name = erl_parse()
%%      Arguments = [Type]
%%      Type = erl_parse()

-doc """
Creates an abstract user type. If `Arguments` is `[T1, ..., Tn]`, the result
represents "`*TypeName*(*T1*, ...*Tn*)`".

_See also: _`type_application/2`, `user_type_application_arguments/1`,
`user_type_application_name/1`.
""".
-spec user_type_application(syntaxTree(), [syntaxTree()]) -> syntaxTree().

user_type_application(TypeName, Arguments) ->
    tree(user_type_application,
         #user_type_application{type_name = TypeName, arguments = Arguments}).

revert_user_type_application(Node) ->
    Pos = get_pos(Node),
    TypeName = user_type_application_name(Node),
    Arguments = user_type_application_arguments(Node),
    {user_type, Pos, atom_value(TypeName), Arguments}.


%% =====================================================================
%% @doc Returns the type name subtree of a `user_type_application' node.
%%
%% @see user_type_application/2

-doc """
Returns the type name subtree of a `user_type_application` node.

_See also: _`user_type_application/2`.
""".
-spec user_type_application_name(syntaxTree()) -> syntaxTree().

user_type_application_name(Node) ->
    case unwrap(Node) of
        {user_type, Pos, Name, _} ->
            set_pos(atom(Name), Pos);
        Node1 ->
            (data(Node1))#user_type_application.type_name
    end.


%% =====================================================================
%% @doc Returns the arguments subtrees of a `user_type_application' node.
%%
%% @see user_type_application/2

-doc """
Returns the arguments subtrees of a `user_type_application` node.

_See also: _`user_type_application/2`.
""".
-spec user_type_application_arguments(syntaxTree()) -> [syntaxTree()].

user_type_application_arguments(Node) ->
    case unwrap(Node) of
        {user_type, _, _, Arguments} ->
            Arguments;
        Node1 ->
            (data(Node1))#user_type_application.arguments
    end.


%% =====================================================================
%% @doc Creates an abstract typed record field specification. The
%% result represents "<code><em>Field</em> :: <em>Type</em></code>".
%%
%% @see typed_record_field_body/1
%% @see typed_record_field_type/1

-record(typed_record_field, {body :: syntaxTree(),
                             type :: syntaxTree()}).

%% type(Node) = typed_record_field
%% data(Node) = #typed_record_field{body :: Field
%%                                  type = Type}
%%
%%      Field = syntaxTree()
%%      Type = syntaxTree()

-doc """
Creates an abstract typed record field specification. The result represents
"`*Field* :: *Type*`".

_See also: _`typed_record_field_body/1`, `typed_record_field_type/1`.
""".
-spec typed_record_field(syntaxTree(), syntaxTree()) -> syntaxTree().

typed_record_field(Field, Type) ->
    tree(typed_record_field,
         #typed_record_field{body = Field, type = Type}).


%% =====================================================================
%% @doc Returns the field subtree of a `typed_record_field' node.
%%
%% @see typed_record_field/2

-doc """
Returns the field subtree of a `typed_record_field` node.

_See also: _`typed_record_field/2`.
""".
-spec typed_record_field_body(syntaxTree()) -> syntaxTree().

typed_record_field_body(Node) ->
    (data(Node))#typed_record_field.body.


%% =====================================================================
%% @doc Returns the type subtree of a `typed_record_field' node.
%%
%% @see typed_record_field/2

-doc """
Returns the type subtree of a `typed_record_field` node.

_See also: _`typed_record_field/2`.
""".
-spec typed_record_field_type(syntaxTree()) -> syntaxTree().

typed_record_field_type(Node) ->
    (data(Node))#typed_record_field.type.


%% =====================================================================
%% @doc Creates an abstract list comprehension. If `Body' is
%% `[E1, ..., En]', the result represents
%% "<code>[<em>Template</em> || <em>E1</em>, ..., <em>En</em>]</code>".
%%
%% @see list_comp_template/1
%% @see list_comp_body/1
%% @see generator/2

-record(list_comp, {template :: syntaxTree(), body :: [syntaxTree()]}).

%% type(Node) = list_comp
%% data(Node) = #list_comp{template :: Template, body :: Body}
%%
%%	Template = Node = syntaxTree()
%%	Body = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {lc, Pos, Template, Body}
%%
%%	Template = erl_parse()
%%	Body = [erl_parse()] \ []

-doc """
Creates an abstract list comprehension. If `Body` is `[E1, ..., En]`, the result
represents "`[*Template* || *E1*, ..., *En*]`".

_See also: _`generator/2`, `list_comp_body/1`, `list_comp_template/1`.
""".
-spec list_comp(syntaxTree(), [syntaxTree()]) -> syntaxTree().

list_comp(Template, Body) ->
    tree(list_comp, #list_comp{template = Template, body = Body}).

revert_list_comp(Node) ->
    Pos = get_pos(Node),
    Template = list_comp_template(Node),
    Body = list_comp_body(Node),
    {lc, Pos, Template, Body}.


%% =====================================================================
%% @doc Returns the template subtree of a `list_comp' node.
%%
%% @see list_comp/2

-doc """
Returns the template subtree of a `list_comp` node.

_See also: _`list_comp/2`.
""".
-spec list_comp_template(syntaxTree()) -> syntaxTree().

list_comp_template(Node) ->
    case unwrap(Node) of
	{lc, _, Template, _} ->
	    Template;
	Node1 ->
	    (data(Node1))#list_comp.template
    end.


%% =====================================================================
%% @doc Returns the list of body subtrees of a `list_comp' node.
%%
%% @see list_comp/2

-doc """
Returns the list of body subtrees of a `list_comp` node.

_See also: _`list_comp/2`.
""".
-spec list_comp_body(syntaxTree()) -> [syntaxTree()].

list_comp_body(Node) ->
    case unwrap(Node) of
	{lc, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#list_comp.body
    end.

%% =====================================================================
%% @doc Creates an abstract binary comprehension. If `Body' is
%% `[E1, ..., En]', the result represents
%% "<code>&lt;&lt;<em>Template</em> || <em>E1</em>, ..., <em>En</em>&gt;&gt;</code>".
%%
%% @see binary_comp_template/1
%% @see binary_comp_body/1
%% @see generator/2

-record(binary_comp, {template :: syntaxTree(), body :: [syntaxTree()]}).

%% type(Node) = binary_comp
%% data(Node) = #binary_comp{template :: Template, body :: Body}
%%
%%	Template = Node = syntaxTree()
%%	Body = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {bc, Pos, Template, Body}
%%
%%	Template = erl_parse()
%%	Body = [erl_parse()] \ []

-doc """
Creates an abstract binary comprehension. If `Body` is `[E1, ..., En]`, the
result represents "`<<*Template* || *E1*, ..., *En*>>`".

_See also: _`binary_comp_body/1`, `binary_comp_template/1`, `generator/2`.
""".
-spec binary_comp(syntaxTree(), [syntaxTree()]) -> syntaxTree().

binary_comp(Template, Body) ->
    tree(binary_comp, #binary_comp{template = Template, body = Body}).

revert_binary_comp(Node) ->
    Pos = get_pos(Node),
    Template = binary_comp_template(Node),
    Body = binary_comp_body(Node),
    {bc, Pos, Template, Body}.


%% =====================================================================
%% @doc Returns the template subtree of a `binary_comp' node.
%%
%% @see binary_comp/2

-doc """
Returns the template subtree of a `binary_comp` node.

_See also: _`binary_comp/2`.
""".
-spec binary_comp_template(syntaxTree()) -> syntaxTree().

binary_comp_template(Node) ->
    case unwrap(Node) of
	{bc, _, Template, _} ->
	    Template;
	Node1 ->
	    (data(Node1))#binary_comp.template
    end.


%% =====================================================================
%% @doc Returns the list of body subtrees of a `binary_comp' node.
%%
%% @see binary_comp/2

-doc """
Returns the list of body subtrees of a `binary_comp` node.

_See also: _`binary_comp/2`.
""".
-spec binary_comp_body(syntaxTree()) -> [syntaxTree()].

binary_comp_body(Node) ->
    case unwrap(Node) of
	{bc, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#binary_comp.body
    end.

%% =====================================================================
%% @doc Creates an abstract map comprehension. If `Body' is
%% `[E1, ..., En]', the result represents
%% "<code>#{<em>Template</em> || <em>E1</em>, ..., <em>En</em>}</code>".
%%
%% @see map_comp_template/1
%% @see map_comp_body/1
%% @see generator/2

-record(map_comp, {template :: syntaxTree(), body :: [syntaxTree()]}).

%% type(Node) = map_comp
%% data(Node) = #map_comp{template :: Template, body :: Body}
%%
%%	Template = Node = syntaxTree()
%%	Body = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {mc, Pos, Template, Body}
%%
%%	Template = erl_parse()
%%	Body = [erl_parse()] \ []

-doc """
Creates an abstract map comprehension. If `Body` is `[E1, ..., En]`, the result
represents "`#{*Template* || *E1*, ..., *En*}`".

_See also: _`generator/2`, `map_comp_body/1`, `map_comp_template/1`.
""".
-spec map_comp(syntaxTree(), [syntaxTree()]) -> syntaxTree().

map_comp(Template, Body) ->
    tree(map_comp, #map_comp{template = Template, body = Body}).

revert_map_comp(Node) ->
    Pos = get_pos(Node),
    Template = map_comp_template(Node),
    Body = map_comp_body(Node),
    {mc, Pos, Template, Body}.


%% =====================================================================
%% @doc Returns the template subtree of a `map_comp' node.
%%
%% @see map_comp/2

-doc """
Returns the template subtree of a `map_comp` node.

_See also: _`map_comp/2`.
""".
-spec map_comp_template(syntaxTree()) -> syntaxTree().

map_comp_template(Node) ->
    case unwrap(Node) of
	{mc, _, Template, _} ->
	    Template;
	Node1 ->
	    (data(Node1))#map_comp.template
    end.


%% =====================================================================
%% @doc Returns the list of body subtrees of a `map_comp' node.
%%
%% @see map_comp/2

-doc """
Returns the list of body subtrees of a `map_comp` node.

_See also: _`map_comp/2`.
""".
-spec map_comp_body(syntaxTree()) -> [syntaxTree()].

map_comp_body(Node) ->
    case unwrap(Node) of
	{mc, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#map_comp.body
    end.

%% =====================================================================
%% @doc Creates an abstract generator. The result represents
%% "<code><em>Pattern</em> &lt;- <em>Body</em></code>".
%%
%% @see generator_pattern/1
%% @see generator_body/1
%% @see list_comp/2
%% @see binary_comp/2

-record(generator, {pattern :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = generator
%% data(Node) = #generator{pattern :: Pattern, body :: Body}
%%
%%	Pattern = Argument = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {generate, Pos, Pattern, Body}
%%
%%	Pattern = Body = erl_parse()

-doc """
Creates an abstract generator. The result represents "`*Pattern*<- *Body*`".

_See also: _`binary_comp/2`, `generator_body/1`, `generator_pattern/1`,
`list_comp/2`.
""".
-spec generator(syntaxTree(), syntaxTree()) -> syntaxTree().

generator(Pattern, Body) ->
    tree(generator, #generator{pattern = Pattern, body = Body}).

revert_generator(Node) ->
    Pos = get_pos(Node),
    Pattern = generator_pattern(Node),
    Body = generator_body(Node),
    {generate, Pos, Pattern, Body}.


%% =====================================================================
%% @doc Returns the pattern subtree of a `generator' node.
%%
%% @see generator/2

-doc """
Returns the pattern subtree of a `generator` node.

_See also: _`generator/2`.
""".
-spec generator_pattern(syntaxTree()) -> syntaxTree().

generator_pattern(Node) ->
    case unwrap(Node) of
	{generate, _, Pattern, _} ->
	    Pattern;
	Node1 ->
	    (data(Node1))#generator.pattern
    end.


%% =====================================================================
%% @doc Returns the body subtree of a `generator' node.
%%
%% @see generator/2

-doc """
Returns the body subtree of a `generator` node.

_See also: _`generator/2`.
""".
-spec generator_body(syntaxTree()) -> syntaxTree().

generator_body(Node) ->
    case unwrap(Node) of
	{generate, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#generator.body
    end.


%% =====================================================================
%% @doc Creates an abstract binary_generator. The result represents
%% "<code><em>Pattern</em> &lt;- <em>Body</em></code>".
%%
%% @see binary_generator_pattern/1
%% @see binary_generator_body/1
%% @see list_comp/2
%% @see binary_comp/2

-record(binary_generator, {pattern :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = binary_generator
%% data(Node) = #binary_generator{pattern :: Pattern, body :: Body}
%%
%%	Pattern = Argument = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {b_generate, Pos, Pattern, Body}
%%
%%	Pattern = Body = erl_parse()

-doc """
Creates an abstract binary_generator. The result represents
"`*Pattern*<- *Body*`".

_See also: _`binary_comp/2`, `binary_generator_body/1`,
`binary_generator_pattern/1`, `list_comp/2`.
""".
-spec binary_generator(syntaxTree(), syntaxTree()) -> syntaxTree().

binary_generator(Pattern, Body) ->
    tree(binary_generator, #binary_generator{pattern = Pattern, body = Body}).

revert_binary_generator(Node) ->
    Pos = get_pos(Node),
    Pattern = binary_generator_pattern(Node),
    Body = binary_generator_body(Node),
    {b_generate, Pos, Pattern, Body}.


%% =====================================================================
%% @doc Returns the pattern subtree of a `generator' node.
%%
%% @see binary_generator/2

-doc """
Returns the pattern subtree of a `generator` node.

_See also: _`binary_generator/2`.
""".
-spec binary_generator_pattern(syntaxTree()) -> syntaxTree().

binary_generator_pattern(Node) ->
    case unwrap(Node) of
	{b_generate, _, Pattern, _} ->
	    Pattern;
	Node1 ->
	    (data(Node1))#binary_generator.pattern
    end.


%% =====================================================================
%% @doc Returns the body subtree of a `generator' node.
%%
%% @see binary_generator/2

-doc """
Returns the body subtree of a `generator` node.

_See also: _`binary_generator/2`.
""".
-spec binary_generator_body(syntaxTree()) -> syntaxTree().

binary_generator_body(Node) ->
    case unwrap(Node) of
	{b_generate, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#binary_generator.body
    end.


%% =====================================================================
%% @doc Creates an abstract map_generator. The result represents
%% "<code><em>Pattern</em> &lt;- <em>Body</em></code>".
%%
%% @see map_generator_pattern/1
%% @see map_generator_body/1
%% @see list_comp/2
%% @see map_comp/2

-record(map_generator, {pattern :: syntaxTree(), body :: syntaxTree()}).

%% type(Node) = map_generator
%% data(Node) = #map_generator{pattern :: Pattern, body :: Body}
%%
%%	Pattern = Argument = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {m_generate, Pos, Pattern, Body}
%%
%%	Pattern = Body = erl_parse()

-doc """
Creates an abstract map_generator. The result represents "`*Pattern*<- *Body*`".

_See also: _`list_comp/2`, `map_comp/2`, `map_generator_body/1`,
`map_generator_pattern/1`.
""".
-spec map_generator(syntaxTree(), syntaxTree()) -> syntaxTree().

map_generator(Pattern, Body) ->
    tree(map_generator, #map_generator{pattern = Pattern, body = Body}).

revert_map_generator(Node) ->
    Pos = get_pos(Node),
    Pattern = map_generator_pattern(Node),
    Body = map_generator_body(Node),
    {m_generate, Pos, Pattern, Body}.


%% =====================================================================
%% @doc Returns the pattern subtree of a `generator' node.
%%
%% @see map_generator/2

-doc """
Returns the pattern subtree of a `generator` node.

_See also: _`map_generator/2`.
""".
-spec map_generator_pattern(syntaxTree()) -> syntaxTree().

map_generator_pattern(Node) ->
    case unwrap(Node) of
	{m_generate, _, Pattern, _} ->
	    Pattern;
	Node1 ->
	    (data(Node1))#map_generator.pattern
    end.


%% =====================================================================
%% @doc Returns the body subtree of a `generator' node.
%%
%% @see map_generator/2

-doc """
Returns the body subtree of a `generator` node.

_See also: _`map_generator/2`.
""".
-spec map_generator_body(syntaxTree()) -> syntaxTree().

map_generator_body(Node) ->
    case unwrap(Node) of
	{m_generate, _, _, Body} ->
	    Body;
	Node1 ->
	    (data(Node1))#map_generator.body
    end.


%% =====================================================================
%% @doc Creates an abstract block expression. If `Body' is
%% `[B1, ..., Bn]', the result represents "<code>begin
%% <em>B1</em>, ..., <em>Bn</em> end</code>".
%%
%% @see block_expr_body/1

%% type(Node) = block_expr
%% data(Node) = Body
%%
%%	Body = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {block, Pos, Body}
%%
%%	    Body = [erl_parse()] \ []

-doc """
Creates an abstract block expression. If `Body` is `[B1, ..., Bn]`, the result
represents "`begin *B1*, ..., *Bn* end`".

_See also: _`block_expr_body/1`.
""".
-spec block_expr([syntaxTree()]) -> syntaxTree().

block_expr(Body) ->
    tree(block_expr, Body).

revert_block_expr(Node) ->
    Pos = get_pos(Node),
    Body = block_expr_body(Node),
    {block, Pos, Body}.


%% =====================================================================
%% @doc Returns the list of body subtrees of a `block_expr' node.
%%
%% @see block_expr/1

-doc """
Returns the list of body subtrees of a `block_expr` node.

_See also: _`block_expr/1`.
""".
-spec block_expr_body(syntaxTree()) -> [syntaxTree()].

block_expr_body(Node) ->
    case unwrap(Node) of
	{block, _, Body} ->
	    Body;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract if-expression. If `Clauses' is
%% `[C1, ..., Cn]', the result represents "<code>if
%% <em>C1</em>; ...; <em>Cn</em> end</code>". More exactly, if each
%% `Ci' represents "<code>() <em>Gi</em> ->
%% <em>Bi</em></code>", then the result represents "<code>if
%% <em>G1</em> -> <em>B1</em>; ...; <em>Gn</em> -> <em>Bn</em>
%% end</code>".
%%
%% @see if_expr_clauses/1
%% @see clause/3
%% @see case_expr/2

%% type(Node) = if_expr
%% data(Node) = Clauses
%%
%%	Clauses = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {'if', Pos, Clauses}
%%
%%	Clauses = [Clause] \ []
%%	Clause = {clause, ...}
%%
%%	See `clause' for documentation on `erl_parse' clauses.

-doc """
Creates an abstract if-expression. If `Clauses` is `[C1, ..., Cn]`, the result
represents "`if *C1*; ...; *Cn* end`". More exactly, if each `Ci` represents
"`() *Gi* -> *Bi*`", then the result represents
"`if *G1* -> *B1*; ...; *Gn* -> *Bn* end`".

_See also: _`case_expr/2`, `clause/3`, `if_expr_clauses/1`.
""".
-spec if_expr([syntaxTree()]) -> syntaxTree().

if_expr(Clauses) ->
    tree(if_expr, Clauses).

revert_if_expr(Node) ->
    Pos = get_pos(Node),
    Clauses = [revert_clause(C) || C <- if_expr_clauses(Node)],
    {'if', Pos, Clauses}.


%% =====================================================================
%% @doc Returns the list of clause subtrees of an `if_expr' node.
%%
%% @see if_expr/1

-doc """
Returns the list of clause subtrees of an `if_expr` node.

_See also: _`if_expr/1`.
""".
-spec if_expr_clauses(syntaxTree()) -> [syntaxTree()].

if_expr_clauses(Node) ->
    case unwrap(Node) of
	{'if', _, Clauses} ->
	    Clauses;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract case-expression. If `Clauses' is
%% `[C1, ..., Cn]', the result represents "<code>case
%% <em>Argument</em> of <em>C1</em>; ...; <em>Cn</em> end</code>". More
%% exactly, if each `Ci' represents "<code>(<em>Pi</em>)
%% <em>Gi</em> -> <em>Bi</em></code>", then the result represents
%% "<code>case <em>Argument</em> of <em>P1</em> <em>G1</em> ->
%% <em>B1</em>; ...; <em>Pn</em> <em>Gn</em> -> <em>Bn</em> end</code>".
%%
%% @see case_expr_clauses/1
%% @see case_expr_argument/1
%% @see clause/3
%% @see if_expr/1

-record(case_expr, {argument :: syntaxTree(), clauses :: [syntaxTree()]}).

%% type(Node) = case_expr
%% data(Node) = #case_expr{argument :: Argument,
%%			   clauses :: Clauses}
%%
%%	Argument = syntaxTree()
%%	Clauses = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {'case', Pos, Argument, Clauses}
%%
%%	Argument = erl_parse()
%%	Clauses = [Clause] \ []
%%	Clause = {clause, ...}
%%
%%	See `clause' for documentation on `erl_parse' clauses.

-doc """
Creates an abstract case-expression. If `Clauses` is `[C1, ..., Cn]`, the result
represents "`case *Argument* of *C1*; ...; *Cn* end`". More exactly, if each
`Ci` represents "`(*Pi*) *Gi* -> *Bi*`", then the result represents
"`case *Argument* of *P1**G1* -> *B1*; ...; *Pn**Gn* -> *Bn* end`".

_See also: _`case_expr_argument/1`, `case_expr_clauses/1`, `clause/3`,
`if_expr/1`.
""".
-spec case_expr(syntaxTree(), [syntaxTree()]) -> syntaxTree().

case_expr(Argument, Clauses) ->
    tree(case_expr, #case_expr{argument = Argument,
			       clauses = Clauses}).

revert_case_expr(Node) ->
    Pos = get_pos(Node),
    Argument = case_expr_argument(Node),
    Clauses = [revert_clause(C) || C <- case_expr_clauses(Node)],
    {'case', Pos, Argument, Clauses}.


%% =====================================================================
%% @doc Returns the argument subtree of a `case_expr' node.
%%
%% @see case_expr/2

-doc """
Returns the argument subtree of a `case_expr` node.

_See also: _`case_expr/2`.
""".
-spec case_expr_argument(syntaxTree()) -> syntaxTree().

case_expr_argument(Node) ->
    case unwrap(Node) of
	{'case', _, Argument, _} ->
	    Argument;
	Node1 ->
	    (data(Node1))#case_expr.argument
    end.


%% =====================================================================
%% @doc Returns the list of clause subtrees of a `case_expr' node.
%%
%% @see case_expr/2

-doc """
Returns the list of clause subtrees of a `case_expr` node.

_See also: _`case_expr/2`.
""".
-spec case_expr_clauses(syntaxTree()) -> [syntaxTree()].

case_expr_clauses(Node) ->
    case unwrap(Node) of
	{'case', _, _, Clauses} ->
	    Clauses;
	Node1 ->
	    (data(Node1))#case_expr.clauses
    end.

%% =====================================================================
%% @doc Creates an abstract else-expression. If `Clauses' is `[C1,
%% ..., Cn]', the result represents "<code>else <em>C1</em>; ...; <em>Cn</em>
%% end</code>". More exactly, if each `Ci' represents
%% "<code>(<em>Pi</em>) <em>Gi</em> -> <em>Bi</em></code>", then the
%% result represents "<code>else <em>G1</em> -> <em>B1</em>; ...;
%% <em>Pn</em> <em>Gn</em> -> <em>Bn</em> end</code>".
%%
%% @see maybe_expr/2
%% @see else_expr_clauses/1
%% @see clause/3

-doc """
Creates an abstract else-expression. If `Clauses` is `[C1, ..., Cn]`, the result
represents "`else *C1*; ...; *Cn* end`". More exactly, if each `Ci` represents
"`(*Pi*) *Gi* -> *Bi*`", then the result represents
"`else *G1* -> *B1*; ...; *Pn**Gn* -> *Bn* end`".

_See also: _`clause/3`, `else_expr_clauses/1`, `maybe_expr/2`.
""".
-spec else_expr([syntaxTree()]) -> syntaxTree().

else_expr(Clauses) ->
    tree(else_expr, Clauses).

revert_else_expr(Node) ->
    Pos = get_pos(Node),
    Clauses = else_expr_clauses(Node),
    {'else', Pos, Clauses}.

%% =====================================================================
%% @doc Returns the list of clause subtrees of an `else_expr' node.
%%
%% @see else_expr/1

-doc """
Returns the list of clause subtrees of an `else_expr` node.

_See also: _`else_expr/1`.
""".
-spec else_expr_clauses(syntaxTree()) -> [syntaxTree()].

else_expr_clauses(Node) ->
    case unwrap(Node) of
	{'else', _, Clauses} ->
	    Clauses;
	Node1 ->
	    data(Node1)
    end.

%% =====================================================================
%% @equiv maybe_expr(Body, none)

-doc "Equivalent to [maybe_expr(Body, none)](`maybe_expr/2`).".
-spec maybe_expr([syntaxTree()]) -> syntaxTree().

maybe_expr(Body) ->
    maybe_expr(Body, none).

%% =====================================================================
%% @doc Creates an abstract maybe-expression. If `Body' is `[B1, ...,
%% Bn]', and `OptionalElse' is `none', the result represents
%% "<code>maybe <em>B1</em>, ..., <em>Bn</em> end</code>".  If `Body'
%% is `[B1, ..., Bn]', and `OptionalElse' reprsents an `else_expr' node
%% with clauses `[C1, ..., Cn]', the result represents "<code>maybe
%% <em>B1</em>, ..., <em>Bn</em> else <em>C1</em>; ..., <em>Cn</em>
%% end</code>".
%%
%%	See `clause' for documentation on `erl_parse' clauses.
%%
%% @see maybe_expr_body/1
%% @see maybe_expr_else/1

-record(maybe_expr, {body :: [syntaxTree()],
                     'else' = none :: 'none' | syntaxTree()}).

%% type(Node) = maybe_expr
%% data(Node) = #maybe_expr{body :: Body, 'else' :: 'none' | Else}
%%
%%     Body = [syntaxTree()]
%%     Else = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {block, Pos, Body}
%% {block, Pos, Body, Else}
%%
%%    Body = [erl_parse()] \ []
%%    Else = {'else', Pos, Clauses}
%%    Clauses = [Clause] \ []
%%    Clause = {clause, ...}

-doc """
Creates an abstract maybe-expression. If `Body` is `[B1, ..., Bn]`, and
`OptionalElse` is `none`, the result represents "`maybe *B1*, ..., *Bn* end`".
If `Body` is `[B1, ..., Bn]`, and `OptionalElse` reprsents an `else_expr` node
with clauses `[C1, ..., Cn]`, the result represents
"`maybe *B1*, ..., *Bn* else *C1*; ..., *Cn* end`".

See `clause` for documentation on `erl_parse` clauses.

_See also: _`maybe_expr_body/1`, `maybe_expr_else/1`.
""".
-spec maybe_expr([syntaxTree()], 'none' | syntaxTree()) -> syntaxTree().

maybe_expr(Body, OptionalElse) ->
    tree(maybe_expr, #maybe_expr{body = Body,
                                 'else' = OptionalElse}).
revert_maybe_expr(Node) ->
    Pos = get_pos(Node),
    Body = maybe_expr_body(Node),
    case maybe_expr_else(Node) of
        none ->
            {'maybe', Pos, Body};
        Else ->
            {'maybe', Pos, Body, Else}
    end.

%% =====================================================================
%% @doc Returns the list of body subtrees of a `maybe_expr' node.
%%
%% @see maybe_expr/2

-doc """
Returns the list of body subtrees of a `maybe_expr` node.

_See also: _`maybe_expr/2`.
""".
-spec maybe_expr_body(syntaxTree()) -> [syntaxTree()].

maybe_expr_body(Node) ->
    case unwrap(Node) of
	{'maybe', _, Body} ->
            Body;
	{'maybe', _, Body, _Else} ->
            Body;
        Node1 ->
            (data(Node1))#maybe_expr.body
    end.

%% =====================================================================
%% @doc Returns the else subtree of a `maybe_expr' node.
%%
%% @see maybe_expr/2

-doc """
Returns the else subtree of a `maybe_expr` node.

_See also: _`maybe_expr/2`.
""".
-spec maybe_expr_else(syntaxTree()) -> 'none' | syntaxTree().

maybe_expr_else(Node) ->
    case unwrap(Node) of
        {'maybe', _, _Body} ->
            none;
        {'maybe', _, _Body, Else} ->
            Else;
        Node1 ->
            (data(Node1))#maybe_expr.'else'
    end.

%% =====================================================================
%% @equiv receive_expr(Clauses, none, [])

-doc "Equivalent to [receive_expr(Clauses, none, [])](`receive_expr/3`).".
-spec receive_expr([syntaxTree()]) -> syntaxTree().

receive_expr(Clauses) ->
    receive_expr(Clauses, none, []).


%% =====================================================================
%% @doc Creates an abstract receive-expression. If `Timeout'
%% is `none', the result represents "<code>receive
%% <em>C1</em>; ...; <em>Cn</em> end</code>" (the `Action'
%% argument is ignored). Otherwise, if `Clauses' is
%% `[C1, ..., Cn]' and `Action' is `[A1, ...,
%% Am]', the result represents "<code>receive <em>C1</em>; ...;
%% <em>Cn</em> after <em>Timeout</em> -> <em>A1</em>, ..., <em>Am</em>
%% end</code>". More exactly, if each `Ci' represents
%% "<code>(<em>Pi</em>) <em>Gi</em> -> <em>Bi</em></code>", then the
%% result represents "<code>receive <em>P1</em> <em>G1</em> ->
%% <em>B1</em>; ...; <em>Pn</em> <em>Gn</em> -> <em>Bn</em> ...
%% end</code>".
%%
%% Note that in Erlang, a receive-expression must have at least one
%% clause if no timeout part is specified.
%%
%% @see receive_expr_clauses/1
%% @see receive_expr_timeout/1
%% @see receive_expr_action/1
%% @see receive_expr/1
%% @see clause/3
%% @see case_expr/2

-record(receive_expr, {clauses :: [syntaxTree()],
		       timeout :: 'none' | syntaxTree(),
		       action  :: [syntaxTree()]}).

%% type(Node) = receive_expr
%% data(Node) = #receive_expr{clauses :: Clauses,
%%			      timeout :: Timeout,
%%			      action :: Action}
%%
%%	Clauses = [syntaxTree()]
%%	Timeout = none | syntaxTree()
%%	Action = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {'receive', Pos, Clauses}
%% {'receive', Pos, Clauses, Timeout, Action}
%%
%%	Clauses = [Clause] \ []
%%	Clause = {clause, ...}
%%	Timeout = erl_parse()
%%	Action = [erl_parse()] \ []
%%
%%	See `clause' for documentation on `erl_parse' clauses.

-doc """
Creates an abstract receive-expression. If `Timeout` is `none`, the result
represents "`receive *C1*; ...; *Cn* end`" (the `Action` argument is ignored).
Otherwise, if `Clauses` is `[C1, ..., Cn]` and `Action` is `[A1, ..., Am]`, the
result represents
"`receive *C1*; ...; *Cn* after *Timeout* -> *A1*, ..., *Am* end`". More
exactly, if each `Ci` represents "`(*Pi*) *Gi* -> *Bi*`", then the result
represents "`receive *P1**G1* -> *B1*; ...; *Pn**Gn* -> *Bn* ... end`".

Note that in Erlang, a receive-expression must have at least one clause if no
timeout part is specified.

_See also: _`case_expr/2`, `clause/3`, `receive_expr/1`,
`receive_expr_action/1`, `receive_expr_clauses/1`, `receive_expr_timeout/1`.
""".
-spec receive_expr([syntaxTree()], 'none' | syntaxTree(), [syntaxTree()]) ->
        syntaxTree().

receive_expr(Clauses, Timeout, Action) ->
    %% If `Timeout' is `none', we always replace the actual
    %% `Action' argument with an empty list, since
    %% `receive_expr_action' should in that case return the empty
    %% list regardless.
    Action1 = case Timeout of
		  none -> [];
		  _ -> Action
	      end,
    tree(receive_expr, #receive_expr{clauses = Clauses,
				     timeout = Timeout,
				     action = Action1}).

revert_receive_expr(Node) ->
    Pos = get_pos(Node),
    Clauses = [revert_clause(C) || C <- receive_expr_clauses(Node)],
    Timeout = receive_expr_timeout(Node),
    Action = receive_expr_action(Node),
    case Timeout of
	none ->
	    {'receive', Pos, Clauses};
	_ ->
	    {'receive', Pos, Clauses, Timeout, Action}
    end.


%% =====================================================================
%% @doc Returns the list of clause subtrees of a
%% `receive_expr' node.
%%
%% @see receive_expr/3

-doc """
Returns the list of clause subtrees of a `receive_expr` node.

_See also: _`receive_expr/3`.
""".
-spec receive_expr_clauses(syntaxTree()) -> [syntaxTree()].

receive_expr_clauses(Node) ->
    case unwrap(Node) of
	{'receive', _, Clauses} ->
	    Clauses;
	{'receive', _, Clauses, _, _} ->
	    Clauses;
	Node1 ->
	    (data(Node1))#receive_expr.clauses
    end.


%% =====================================================================
%% @doc Returns the timeout subtree of a `receive_expr' node,
%% if any. If `Node' represents "<code>receive <em>C1</em>;
%% ...; <em>Cn</em> end</code>", `none' is returned.
%% Otherwise, if `Node' represents "<code>receive
%% <em>C1</em>; ...; <em>Cn</em> after <em>Timeout</em> -> ... end</code>",
%% `Timeout' is returned.
%%
%% @see receive_expr/3

-doc """
Returns the timeout subtree of a `receive_expr` node, if any. If `Node`
represents "`receive *C1*; ...; *Cn* end`", `none` is returned. Otherwise, if
`Node` represents "`receive *C1*; ...; *Cn* after *Timeout* -> ... end`",
`Timeout` is returned.

_See also: _`receive_expr/3`.
""".
-spec receive_expr_timeout(syntaxTree()) -> 'none' | syntaxTree().

receive_expr_timeout(Node) ->
    case unwrap(Node) of
	{'receive', _, _} ->
	    none;
	{'receive', _, _, Timeout, _} ->
	    Timeout;
	Node1 ->
	    (data(Node1))#receive_expr.timeout
    end.


%% =====================================================================
%% @doc Returns the list of action body subtrees of a
%% `receive_expr' node. If `Node' represents
%% "<code>receive <em>C1</em>; ...; <em>Cn</em> end</code>", this is the
%% empty list.
%%
%% @see receive_expr/3

-doc """
Returns the list of action body subtrees of a `receive_expr` node. If `Node`
represents "`receive *C1*; ...; *Cn* end`", this is the empty list.

_See also: _`receive_expr/3`.
""".
-spec receive_expr_action(syntaxTree()) -> [syntaxTree()].

receive_expr_action(Node) ->
    case unwrap(Node) of
	{'receive', _, _} ->
	    [];
	{'receive', _, _, _, Action} ->
	    Action;
	Node1 ->
	    (data(Node1))#receive_expr.action
    end.


%% =====================================================================
%% @equiv try_expr(Body, [], Handlers)

-doc "Equivalent to [try_expr(Body, [], Handlers)](`try_expr/3`).".
-spec try_expr([syntaxTree()], [syntaxTree()]) -> syntaxTree().

try_expr(Body, Handlers) ->
    try_expr(Body, [], Handlers).


%% =====================================================================
%% @equiv try_expr(Body, Clauses, Handlers, [])

-doc "Equivalent to [try_expr(Body, Clauses, Handlers, [])](`try_expr/4`).".
-spec try_expr([syntaxTree()], [syntaxTree()], [syntaxTree()]) -> syntaxTree().

try_expr(Body, Clauses, Handlers) ->
    try_expr(Body, Clauses, Handlers, []).


%% =====================================================================
%% @equiv try_expr(Body, [], [], After)

-doc "Equivalent to [try_expr(Body, [], [], After)](`try_expr/4`).".
-spec try_after_expr([syntaxTree()], [syntaxTree()]) -> syntaxTree().

try_after_expr(Body, After) ->
    try_expr(Body, [], [], After).


%% =====================================================================
%% @doc Creates an abstract try-expression. If `Body' is
%% `[B1, ..., Bn]', `Clauses' is `[C1, ...,
%% Cj]', `Handlers' is `[H1, ..., Hk]', and
%% `After' is `[A1, ..., Am]', the result
%% represents "<code>try <em>B1</em>, ..., <em>Bn</em> of <em>C1</em>;
%% ...; <em>Cj</em> catch <em>H1</em>; ...; <em>Hk</em> after
%% <em>A1</em>, ..., <em>Am</em> end</code>". More exactly, if each
%% `Ci' represents "<code>(<em>CPi</em>) <em>CGi</em> ->
%% <em>CBi</em></code>", and each `Hi' represents
%% "<code>(<em>HPi</em>) <em>HGi</em> -> <em>HBi</em></code>", then the
%% result represents "<code>try <em>B1</em>, ..., <em>Bn</em> of
%% <em>CP1</em> <em>CG1</em> -> <em>CB1</em>; ...; <em>CPj</em>
%% <em>CGj</em> -> <em>CBj</em> catch <em>HP1</em> <em>HG1</em> ->
%% <em>HB1</em>; ...; <em>HPk</em> <em>HGk</em> -> <em>HBk</em> after
%% <em>A1</em>, ..., <em>Am</em> end</code>"; see
%% {@link case_expr/2}. If `Clauses' is the empty list,
%% the `of ...' section is left out. If `After' is
%% the empty list, the `after ...' section is left out. If
%% `Handlers' is the empty list, and `After' is
%% nonempty, the `catch ...' section is left out.
%%
%% @see try_expr_body/1
%% @see try_expr_clauses/1
%% @see try_expr_handlers/1
%% @see try_expr_after/1
%% @see try_expr/2
%% @see try_expr/3
%% @see try_after_expr/2
%% @see clause/3
%% @see class_qualifier/2
%% @see case_expr/2

-record(try_expr, {body     :: [syntaxTree()],
		   clauses  :: [syntaxTree()],
		   handlers :: [syntaxTree()],
		   'after'  :: [syntaxTree()]}).

%% type(Node) = try_expr
%% data(Node) = #try_expr{body :: Body,
%%			  clauses :: Clauses,
%%			  handlers :: Clauses,
%%			  after :: Body}
%%
%%	Body = syntaxTree()
%%	Clauses = [syntaxTree()]
%%
%% `erl_parse' representation:
%%
%% {'try', Pos, Body, Clauses, Handlers, After}
%%
%%	Body = [erl_parse()]
%%	Clauses = [Clause]
%%	Handlers = [Clause] \ []
%%	Clause = {clause, ...}
%%	After = [erl_parse()]
%%
%%	See `clause' for documentation on `erl_parse' clauses.

-doc """
Creates an abstract try-expression. If `Body` is `[B1, ..., Bn]`, `Clauses` is
`[C1, ..., Cj]`, `Handlers` is `[H1, ..., Hk]`, and `After` is `[A1, ..., Am]`,
the result represents
"`try *B1*, ..., *Bn* of *C1*; ...; *Cj* catch *H1*; ...; *Hk* after *A1*, ..., *Am* end`".
More exactly, if each `Ci` represents "`(*CPi*) *CGi* -> *CBi*`", and each `Hi`
represents "`(*HPi*) *HGi* -> *HBi*`", then the result represents
"`try *B1*, ..., *Bn* of *CP1**CG1* -> *CB1*; ...; *CPj**CGj* -> *CBj* catch *HP1**HG1* -> *HB1*; ...; *HPk**HGk* -> *HBk* after *A1*, ..., *Am* end`";
see `case_expr/2`. If `Clauses` is the empty list, the `of ...` section is left
out. If `After` is the empty list, the `after ...` section is left out. If
`Handlers` is the empty list, and `After` is nonempty, the `catch ...` section
is left out.

_See also: _`case_expr/2`, `class_qualifier/2`, `clause/3`, `try_after_expr/2`,
`try_expr/2`, `try_expr/3`, `try_expr_after/1`, `try_expr_body/1`,
`try_expr_clauses/1`, `try_expr_handlers/1`.
""".
-spec try_expr([syntaxTree()], [syntaxTree()],
	       [syntaxTree()], [syntaxTree()]) -> syntaxTree().

try_expr(Body, Clauses, Handlers, After) ->
    tree(try_expr, #try_expr{body = Body,
			     clauses = Clauses,
			     handlers = Handlers,
			     'after' = After}).

revert_try_expr(Node) ->
    Pos = get_pos(Node),
    Body = try_expr_body(Node),
    Clauses = [revert_clause(C) || C <- try_expr_clauses(Node)],
    Handlers = [revert_try_clause(C) || C <- try_expr_handlers(Node)],
    After = try_expr_after(Node),
    {'try', Pos, Body, Clauses, Handlers, After}.


%% =====================================================================
%% @doc Returns the list of body subtrees of a `try_expr' node.
%%
%% @see try_expr/4

-doc """
Returns the list of body subtrees of a `try_expr` node.

_See also: _`try_expr/4`.
""".
-spec try_expr_body(syntaxTree()) -> [syntaxTree()].

try_expr_body(Node) ->
    case unwrap(Node) of
	{'try', _, Body, _, _, _} ->
	    Body;
	Node1 ->
	    (data(Node1))#try_expr.body
    end.


%% =====================================================================
%% @doc Returns the list of case-clause subtrees of a
%% `try_expr' node. If `Node' represents
%% "<code>try <em>Body</em> catch <em>H1</em>; ...; <em>Hn</em>
%% end</code>", the result is the empty list.
%%
%% @see try_expr/4

-doc """
Returns the list of case-clause subtrees of a `try_expr` node. If `Node`
represents "`try *Body* catch *H1*; ...; *Hn* end`", the result is the empty
list.

_See also: _`try_expr/4`.
""".
-spec try_expr_clauses(syntaxTree()) -> [syntaxTree()].

try_expr_clauses(Node) ->
    case unwrap(Node) of
	{'try', _, _, Clauses, _, _} ->
	    Clauses;
	Node1 ->
	    (data(Node1))#try_expr.clauses
    end.


%% =====================================================================
%% @doc Returns the list of handler-clause subtrees of a
%% `try_expr' node.
%%
%% @see try_expr/4

-doc """
Returns the list of handler-clause subtrees of a `try_expr` node.

_See also: _`try_expr/4`.
""".
-spec try_expr_handlers(syntaxTree()) -> [syntaxTree()].

try_expr_handlers(Node) ->
    case unwrap(Node) of
	{'try', _, _, _, Handlers, _} ->
	    unfold_try_clauses(Handlers);
	Node1 ->
	    (data(Node1))#try_expr.handlers
    end.


%% =====================================================================
%% @doc Returns the list of "after" subtrees of a `try_expr' node.
%%
%% @see try_expr/4

-doc """
Returns the list of "after" subtrees of a `try_expr` node.

_See also: _`try_expr/4`.
""".
-spec try_expr_after(syntaxTree()) -> [syntaxTree()].

try_expr_after(Node) ->
    case unwrap(Node) of
	{'try', _, _, _, _, After} ->
	    After;
	Node1 ->
	    (data(Node1))#try_expr.'after'
    end.


%% =====================================================================
%% @doc Creates an abstract class qualifier. The result represents
%% "<code><em>Class</em>:<em>Body</em></code>".
%%
%% @see class_qualifier_argument/1
%% @see class_qualifier_body/1
%% @see class_qualifier_stacktrace/1
%% @see try_expr/4

-record(class_qualifier, {class :: syntaxTree(),
                          body :: syntaxTree(),
                          stacktrace :: syntaxTree()}).

%% type(Node) = class_qualifier
%% data(Node) = #class_qualifier{class :: Class, body :: Body}
%%
%%	Class = Body = syntaxTree()

-doc """
Creates an abstract class qualifier. The result represents "`*Class*:*Body*`".

_See also: _`class_qualifier_argument/1`, `class_qualifier_body/1`,
`class_qualifier_stacktrace/1`, `try_expr/4`.
""".
-spec class_qualifier(syntaxTree(), syntaxTree()) -> syntaxTree().

class_qualifier(Class, Body) ->
    Underscore = {var, get_pos(Body), '_'},
    tree(class_qualifier,
	 #class_qualifier{class = Class, body = Body,
                          stacktrace = Underscore}).

%% =====================================================================
%% @doc Creates an abstract class qualifier. The result represents
%% "<code><em>Class</em>:<em>Body</em>:<em>Stacktrace</em></code>".
%%
%% @see class_qualifier_argument/1
%% @see class_qualifier_body/1
%% @see try_expr/4

-doc """
Creates an abstract class qualifier. The result represents
"`*Class*:*Body*:*Stacktrace*`".

_See also: _`class_qualifier_argument/1`, `class_qualifier_body/1`,
`try_expr/4`.
""".
-spec class_qualifier(syntaxTree(), syntaxTree(), syntaxTree()) ->
                             syntaxTree().

class_qualifier(Class, Body, Stacktrace) ->
    tree(class_qualifier,
	 #class_qualifier{class = Class,
                          body = Body,
                          stacktrace = Stacktrace}).


%% =====================================================================
%% @doc Returns the argument (the class) subtree of a
%% `class_qualifier' node.
%%
%% @see class_qualifier/2

-doc """
Returns the argument (the class) subtree of a `class_qualifier` node.

_See also: _`class_qualifier/2`.
""".
-spec class_qualifier_argument(syntaxTree()) -> syntaxTree().

class_qualifier_argument(Node) ->
    (data(Node))#class_qualifier.class.


%% =====================================================================
%% @doc Returns the body subtree of a `class_qualifier' node.
%%
%% @see class_qualifier/2

-doc """
Returns the body subtree of a `class_qualifier` node.

_See also: _`class_qualifier/2`.
""".
-spec class_qualifier_body(syntaxTree()) -> syntaxTree().

class_qualifier_body(Node) ->
    (data(Node))#class_qualifier.body.

%% =====================================================================
%% @doc Returns the stacktrace subtree of a `class_qualifier' node.
%%
%% @see class_qualifier/2

-doc """
Returns the stacktrace subtree of a `class_qualifier` node.

_See also: _`class_qualifier/2`.
""".
-spec class_qualifier_stacktrace(syntaxTree()) -> syntaxTree().

class_qualifier_stacktrace(Node) ->
    (data(Node))#class_qualifier.stacktrace.


%% =====================================================================
%% @doc Creates an abstract "implicit fun" expression. If
%% `Arity' is `none', this is equivalent to
%% `implicit_fun(Name)', otherwise it is equivalent to
%% `implicit_fun(arity_qualifier(Name, Arity))'.
%%
%% (This is a utility function.)
%%
%% @see implicit_fun/1
%% @see implicit_fun/3

-doc """
Creates an abstract "implicit fun" expression. If `Arity` is `none`, this is
equivalent to [`implicit_fun(Name)`](`implicit_fun/1`), otherwise it is
equivalent to [`implicit_fun(arity_qualifier(Name, Arity))`](`implicit_fun/1`).

(This is a utility function.)

_See also: _`implicit_fun/1`, `implicit_fun/3`.
""".
-spec implicit_fun(syntaxTree(), 'none' | syntaxTree()) -> syntaxTree().

implicit_fun(Name, none) ->
    implicit_fun(Name);
implicit_fun(Name, Arity) ->
    implicit_fun(arity_qualifier(Name, Arity)).


%% =====================================================================
%% @doc Creates an abstract module-qualified "implicit fun" expression.
%% If `Module' is `none', this is equivalent to
%% `implicit_fun(Name, Arity)', otherwise it is equivalent to
%% `implicit_fun(module_qualifier(Module, arity_qualifier(Name,
%% Arity))'.
%%
%% (This is a utility function.)
%%
%% @see implicit_fun/1
%% @see implicit_fun/2

-doc """
Creates an abstract module-qualified "implicit fun" expression. If `Module` is
`none`, this is equivalent to [`implicit_fun(Name, Arity)`](`implicit_fun/2`),
otherwise it is equivalent to
`implicit_fun(module_qualifier(Module, arity_qualifier(Name, Arity))`.

(This is a utility function.)

_See also: _`implicit_fun/1`, `implicit_fun/2`.
""".
-spec implicit_fun('none' | syntaxTree(), syntaxTree(), syntaxTree()) ->
        syntaxTree().

implicit_fun(none, Name, Arity) ->
    implicit_fun(Name, Arity);
implicit_fun(Module, Name, Arity) ->
    implicit_fun(module_qualifier(Module, arity_qualifier(Name, Arity))).


%% =====================================================================
%% @doc Creates an abstract "implicit fun" expression. The result
%% represents "<code>fun <em>Name</em></code>". `Name' should
%% represent either <code><em>F</em>/<em>A</em></code> or
%% <code><em>M</em>:<em>F</em>/<em>A</em></code>
%%
%% @see implicit_fun_name/1
%% @see implicit_fun/2
%% @see implicit_fun/3
%% @see arity_qualifier/2
%% @see module_qualifier/2

%% type(Node) = implicit_fun
%% data(Node) = syntaxTree()
%%
%% `erl_parse' representation:
%%
%% {'fun', Pos, {function, Name, Arity}}
%% {'fun', Pos, {function, Module, Name, Arity}}
%%
%%	Module = atom()
%%	Name = atom()
%%	Arity = arity()

-doc """
Creates an abstract "implicit fun" expression. The result represents
"`fun *Name*`". `Name` should represent either `*F*/*A*` or `*M*:*F*/*A*`

_See also: _`arity_qualifier/2`, `implicit_fun/2`, `implicit_fun/3`,
`implicit_fun_name/1`, `module_qualifier/2`.
""".
-spec implicit_fun(syntaxTree()) -> syntaxTree().

implicit_fun(Name) ->
    tree(implicit_fun, Name).

revert_implicit_fun(Node) ->
    Pos = get_pos(Node),
    Name = implicit_fun_name(Node),
    case type(Name) of
	arity_qualifier ->
	    F = arity_qualifier_body(Name),
	    A = arity_qualifier_argument(Name),
	    case {type(F), type(A)} of
		{atom, integer} ->
		    {'fun', Pos,
		     {function, concrete(F), concrete(A)}};
		_ ->
		    Node
	    end;
	module_qualifier ->
	    M = module_qualifier_argument(Name),
	    Name1 = module_qualifier_body(Name),
	    case type(Name1) of
		arity_qualifier ->
		    F = arity_qualifier_body(Name1),
		    A = arity_qualifier_argument(Name1),
		    {'fun', Pos, {function, M, F, A}};
		_ ->
		    Node
	    end;
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the name subtree of an `implicit_fun' node.
%%
%% Note: if `Node' represents "<code>fun
%% <em>N</em>/<em>A</em></code>" or "<code>fun
%% <em>M</em>:<em>N</em>/<em>A</em></code>", then the result is the
%% subtree representing "<code><em>N</em>/<em>A</em></code>" or
%% "<code><em>M</em>:<em>N</em>/<em>A</em></code>", respectively.
%%
%% @see implicit_fun/1
%% @see arity_qualifier/2
%% @see module_qualifier/2

-doc """
Returns the name subtree of an `implicit_fun` node.

Note: if `Node` represents "`fun *N*/*A*`" or "`fun *M*:*N*/*A*`", then the
result is the subtree representing "`*N*/*A*`" or "`*M*:*N*/*A*`", respectively.

_See also: _`arity_qualifier/2`, `implicit_fun/1`, `module_qualifier/2`.
""".
-spec implicit_fun_name(syntaxTree()) -> syntaxTree().

implicit_fun_name(Node) ->
    case unwrap(Node) of
	{'fun', Pos, {function, Atom, Arity}} ->
	    arity_qualifier(set_pos(atom(Atom), Pos),
			    set_pos(integer(Arity), Pos));
	{'fun', _Pos, {function, Module, Atom, Arity}} ->
	    %% XXX: Perhaps set position for this as well?
	    module_qualifier(Module, arity_qualifier(Atom, Arity));
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Creates an abstract fun-expression. If `Clauses' is
%% `[C1, ..., Cn]', the result represents "<code>fun
%% <em>C1</em>; ...; <em>Cn</em> end</code>". More exactly, if each
%% `Ci' represents "<code>(<em>Pi1</em>, ..., <em>Pim</em>)
%% <em>Gi</em> -> <em>Bi</em></code>", then the result represents
%% "<code>fun (<em>P11</em>, ..., <em>P1m</em>) <em>G1</em> ->
%% <em>B1</em>; ...; (<em>Pn1</em>, ..., <em>Pnm</em>) <em>Gn</em> ->
%% <em>Bn</em> end</code>".
%%
%% @see fun_expr_clauses/1
%% @see fun_expr_arity/1

%% type(Node) = fun_expr
%% data(Node) = Clauses
%%
%%	Clauses = [syntaxTree()]
%%
%%	(See `function' for notes; e.g. why the arity is not stored.)
%%
%% `erl_parse' representation:
%%
%% {'fun', Pos, {clauses, Clauses}}
%%
%%	Clauses = [Clause] \ []
%%	Clause = {clause, ...}
%%
%%	See `clause' for documentation on `erl_parse' clauses.

-doc """
Creates an abstract fun-expression. If `Clauses` is `[C1, ..., Cn]`, the result
represents "`fun *C1*; ...; *Cn* end`". More exactly, if each `Ci` represents
"`(*Pi1*, ..., *Pim*) *Gi* -> *Bi*`", then the result represents
"`fun (*P11*, ..., *P1m*) *G1* -> *B1*; ...; (*Pn1*, ..., *Pnm*) *Gn* -> *Bn* end`".

_See also: _`fun_expr_arity/1`, `fun_expr_clauses/1`.
""".
-spec fun_expr([syntaxTree()]) -> syntaxTree().

fun_expr(Clauses) ->
    tree(fun_expr, Clauses).

revert_fun_expr(Node) ->
    Clauses = [revert_clause(C) || C <- fun_expr_clauses(Node)],
    Pos = get_pos(Node),
    {'fun', Pos, {clauses, Clauses}}.


%% =====================================================================
%% @doc Returns the list of clause subtrees of a `fun_expr' node.
%%
%% @see fun_expr/1

-doc """
Returns the list of clause subtrees of a `fun_expr` node.

_See also: _`fun_expr/1`.
""".
-spec fun_expr_clauses(syntaxTree()) -> [syntaxTree()].

fun_expr_clauses(Node) ->
    case unwrap(Node) of
	{'fun', _, {clauses, Clauses}} ->
	    Clauses;
	Node1 ->
	    data(Node1)
    end.


%% =====================================================================
%% @doc Returns the arity of a `fun_expr' node. The result is
%% the number of parameter patterns in the first clause of the
%% fun-expression; subsequent clauses are ignored.
%%
%% An exception is thrown if `fun_expr_clauses(Node)'
%% returns an empty list, or if the first element of that list is not a
%% syntax tree `C' of type `clause' such that
%% `clause_patterns(C)' is a nonempty list.
%%
%% @see fun_expr/1
%% @see fun_expr_clauses/1
%% @see clause/3
%% @see clause_patterns/1

-doc """
Returns the arity of a `fun_expr` node. The result is the number of parameter
patterns in the first clause of the fun-expression; subsequent clauses are
ignored.

An exception is thrown if [`fun_expr_clauses(Node)`](`fun_expr_clauses/1`)
returns an empty list, or if the first element of that list is not a syntax tree
`C` of type `clause` such that [`clause_patterns(C)`](`clause_patterns/1`) is a
nonempty list.

_See also: _`clause/3`, `clause_patterns/1`, `fun_expr/1`, `fun_expr_clauses/1`.
""".
-spec fun_expr_arity(syntaxTree()) -> arity().

fun_expr_arity(Node) ->
    length(clause_patterns(hd(fun_expr_clauses(Node)))).


%% =====================================================================
%% @doc Creates an abstract named fun-expression. If `Clauses' is
%% `[C1, ..., Cn]', the result represents "<code>fun
%% <em>Name</em> <em>C1</em>; ...; <em>Name</em> <em>Cn</em> end</code>".
%% More exactly, if each `Ci' represents
%% "<code>(<em>Pi1</em>, ..., <em>Pim</em>) <em>Gi</em> -> <em>Bi</em></code>",
%% then the result represents
%% "<code>fun <em>Name</em>(<em>P11</em>, ..., <em>P1m</em>) <em>G1</em> ->
%% <em>B1</em>; ...; <em>Name</em>(<em>Pn1</em>, ..., <em>Pnm</em>)
%% <em>Gn</em> -> <em>Bn</em> end</code>".
%%
%% @see named_fun_expr_name/1
%% @see named_fun_expr_clauses/1
%% @see named_fun_expr_arity/1

-record(named_fun_expr, {name :: syntaxTree(), clauses :: [syntaxTree()]}).

%% type(Node) = named_fun_expr
%% data(Node) = #named_fun_expr{name :: Name, clauses :: Clauses}
%%
%%	Name = syntaxTree()
%%	Clauses = [syntaxTree()]
%%
%%	(See `function' for notes; e.g. why the arity is not stored.)
%%
%% `erl_parse' representation:
%%
%% {named_fun, Pos, Name, Clauses}
%%
%%	Clauses = [Clause] \ []
%%	Clause = {clause, ...}
%%
%%	See `clause' for documentation on `erl_parse' clauses.

-doc """
Creates an abstract named fun-expression. If `Clauses` is `[C1, ..., Cn]`, the
result represents "`fun *Name**C1*; ...; *Name**Cn* end`". More exactly, if each
`Ci` represents "`(*Pi1*, ..., *Pim*) *Gi* -> *Bi*`", then the result represents
"`fun *Name*(*P11*, ..., *P1m*) *G1* -> *B1*; ...; *Name*(*Pn1*, ..., *Pnm*) *Gn* -> *Bn* end`".

_See also: _`named_fun_expr_arity/1`, `named_fun_expr_clauses/1`,
`named_fun_expr_name/1`.
""".
-spec named_fun_expr(syntaxTree(), [syntaxTree()]) -> syntaxTree().

named_fun_expr(Name, Clauses) ->
    tree(named_fun_expr, #named_fun_expr{name = Name, clauses = Clauses}).

revert_named_fun_expr(Node) ->
    Pos = get_pos(Node),
    Name = named_fun_expr_name(Node),
    Clauses = [revert_clause(C) || C <- named_fun_expr_clauses(Node)],
    case type(Name) of
	variable ->
	    {named_fun, Pos, variable_name(Name), Clauses};
	_ ->
	    Node
    end.


%% =====================================================================
%% @doc Returns the name subtree of a `named_fun_expr' node.
%%
%% @see named_fun_expr/2

-doc """
Returns the name subtree of a `named_fun_expr` node.

_See also: _`named_fun_expr/2`.
""".
-spec named_fun_expr_name(syntaxTree()) -> syntaxTree().

named_fun_expr_name(Node) ->
    case unwrap(Node) of
	{named_fun, Pos, Name, _} ->
	    set_pos(variable(Name), Pos);
	Node1 ->
	    (data(Node1))#named_fun_expr.name
    end.


%% =====================================================================
%% @doc Returns the list of clause subtrees of a `named_fun_expr' node.
%%
%% @see named_fun_expr/2

-doc """
Returns the list of clause subtrees of a `named_fun_expr` node.

_See also: _`named_fun_expr/2`.
""".
-spec named_fun_expr_clauses(syntaxTree()) -> [syntaxTree()].

named_fun_expr_clauses(Node) ->
    case unwrap(Node) of
	{named_fun, _, _, Clauses} ->
	    Clauses;
	Node1 ->
	    (data(Node1))#named_fun_expr.clauses
    end.


%% =====================================================================
%% @doc Returns the arity of a `named_fun_expr' node. The result is
%% the number of parameter patterns in the first clause of the
%% named fun-expression; subsequent clauses are ignored.
%%
%% An exception is thrown if `named_fun_expr_clauses(Node)'
%% returns an empty list, or if the first element of that list is not a
%% syntax tree `C' of type `clause' such that
%% `clause_patterns(C)' is a nonempty list.
%%
%% @see named_fun_expr/2
%% @see named_fun_expr_clauses/1
%% @see clause/3
%% @see clause_patterns/1

-doc """
Returns the arity of a `named_fun_expr` node. The result is the number of
parameter patterns in the first clause of the named fun-expression; subsequent
clauses are ignored.

An exception is thrown if
[`named_fun_expr_clauses(Node)`](`named_fun_expr_clauses/1`) returns an empty
list, or if the first element of that list is not a syntax tree `C` of type
`clause` such that [`clause_patterns(C)`](`clause_patterns/1`) is a nonempty
list.

_See also: _`clause/3`, `clause_patterns/1`, `named_fun_expr/2`,
`named_fun_expr_clauses/1`.
""".
-spec named_fun_expr_arity(syntaxTree()) -> arity().

named_fun_expr_arity(Node) ->
    length(clause_patterns(hd(named_fun_expr_clauses(Node)))).


%% =====================================================================
%% @doc Creates an abstract parenthesised expression. The result
%% represents "<code>(<em>Body</em>)</code>", independently of the
%% context.
%%
%% @see parentheses_body/1

%% type(Node) = parentheses
%% data(Node) = syntaxTree()

-doc """
Creates an abstract parenthesised expression. The result represents
"`(*Body*)`", independently of the context.

_See also: _`parentheses_body/1`.
""".
-spec parentheses(syntaxTree()) -> syntaxTree().

parentheses(Expr) ->
    tree(parentheses, Expr).

revert_parentheses(Node) ->
    parentheses_body(Node).


%% =====================================================================
%% @doc Returns the body subtree of a `parentheses' node.
%%
%% @see parentheses/1

-doc """
Returns the body subtree of a `parentheses` node.

_See also: _`parentheses/1`.
""".
-spec parentheses_body(syntaxTree()) -> syntaxTree().

parentheses_body(Node) ->
    data(Node).


%% =====================================================================
%% @equiv macro(Name, none)

-doc "Equivalent to [macro(Name, none)](`macro/2`).".
-spec macro(syntaxTree()) -> syntaxTree().

macro(Name) ->
    macro(Name, none).


%% =====================================================================
%% @doc Creates an abstract macro application. If `Arguments'
%% is `none', the result represents
%% "<code>?<em>Name</em></code>", otherwise, if `Arguments'
%% is `[A1, ..., An]', the result represents
%% "<code>?<em>Name</em>(<em>A1</em>, ..., <em>An</em>)</code>".
%%
%% Notes: if `Arguments' is the empty list, the result
%% will thus represent "<code>?<em>Name</em>()</code>", including a pair
%% of matching parentheses.
%%
%% The only syntactical limitation imposed by the preprocessor on the
%% arguments to a macro application (viewed as sequences of tokens) is
%% that they must be balanced with respect to parentheses, brackets,
%% `begin ... end', `case ... end', etc. The
%% `text' node type can be used to represent arguments which
%% are not regular Erlang constructs.
%%
%% @see macro_name/1
%% @see macro_arguments/1
%% @see macro/1
%% @see text/1

-record(macro, {name :: syntaxTree(), arguments :: 'none' | [syntaxTree()]}).

%% type(Node) = macro
%% data(Node) = #macro{name :: Name, arguments :: Arguments}
%%
%%	Name = syntaxTree()
%%	Arguments = none | [syntaxTree()]

-doc """
Creates an abstract macro application. If `Arguments` is `none`, the result
represents "`?*Name*`", otherwise, if `Arguments` is `[A1, ..., An]`, the result
represents "`?*Name*(*A1*, ..., *An*)`".

Notes: if `Arguments` is the empty list, the result will thus represent
"`?*Name*()`", including a pair of matching parentheses.

The only syntactical limitation imposed by the preprocessor on the arguments to
a macro application (viewed as sequences of tokens) is that they must be
balanced with respect to parentheses, brackets, `begin ... end`, `case ... end`,
etc. The `text` node type can be used to represent arguments which are not
regular Erlang constructs.

_See also: _`macro/1`, `macro_arguments/1`, `macro_name/1`, `text/1`.
""".
-spec macro(syntaxTree(), 'none' | [syntaxTree()]) -> syntaxTree().

macro(Name, Arguments) ->
    tree(macro, #macro{name = Name, arguments = Arguments}).


%% =====================================================================
%% @doc Returns the name subtree of a `macro' node.
%%
%% @see macro/2

-doc """
Returns the name subtree of a `macro` node.

_See also: _`macro/2`.
""".
-spec macro_name(syntaxTree()) -> syntaxTree().

macro_name(Node) ->
    (data(Node))#macro.name.


%% =====================================================================
%% @doc Returns the list of argument subtrees of a `macro'
%% node, if any. If `Node' represents
%% "<code>?<em>Name</em></code>", `none' is returned.
%% Otherwise, if `Node' represents
%% "<code>?<em>Name</em>(<em>A1</em>, ..., <em>An</em>)</code>",
%% `[A1, ..., An]' is returned.
%%
%% @see macro/2

-doc """
Returns the list of argument subtrees of a `macro` node, if any. If `Node`
represents "`?*Name*`", `none` is returned. Otherwise, if `Node` represents
"`?*Name*(*A1*, ..., *An*)`", `[A1, ..., An]` is returned.

_See also: _`macro/2`.
""".
-spec macro_arguments(syntaxTree()) -> 'none' | [syntaxTree()].

macro_arguments(Node) ->
    (data(Node))#macro.arguments.


%% =====================================================================
%% @doc Returns the syntax tree corresponding to an Erlang term.
%% `Term' must be a literal term, i.e., one that can be
%% represented as a source code literal. Thus, it may not contain a
%% process identifier, port, reference or function value as a
%% subterm. The function recognises printable strings, in order to get a
%% compact and readable representation. Evaluation fails with reason
%% `badarg' if `Term' is not a literal term.
%%
%% @see concrete/1
%% @see is_literal/1

-doc """
Returns the syntax tree corresponding to an Erlang term. `Term` must be a
literal term, i.e., one that can be represented as a source code literal. Thus,
it may not contain a process identifier, port, reference or function value as a
subterm. The function recognises printable strings, in order to get a compact
and readable representation. Evaluation fails with reason `badarg` if `Term` is
not a literal term.

_See also: _`concrete/1`, `is_literal/1`.
""".
-spec abstract(term()) -> syntaxTree().

abstract([H | T] = L) when is_integer(H) ->
    case is_printable(L) of
	true ->
	    string(L);
	false ->
	    abstract_tail(H, T)
    end;
abstract([H | T]) ->
    abstract_tail(H, T);
abstract(T) when is_atom(T) ->
    atom(T);
abstract(T) when is_integer(T) ->
    integer(T);
abstract(T) when is_float(T) ->
    make_float(T);    % (not `float', which would call the BIF)
abstract([]) ->
    nil();
abstract(T) when is_tuple(T) ->
    tuple(abstract_list(tuple_to_list(T)));
abstract(T) when is_map(T) ->
    map_expr([map_field_assoc(abstract(Key),abstract(Value))
	      || {Key,Value} <- maps:to_list(T)]);
abstract(T) when is_binary(T) ->
    binary([binary_field(integer(B)) || B <- binary_to_list(T)]);
abstract(T) when is_bitstring(T) ->
    S = bit_size(T),
    ByteS = S div 8,
    BitS = S rem 8,
    <<Bin:ByteS/binary, I:BitS>> = T,
    binary([binary_field(integer(B)) || B <- binary_to_list(Bin)]
           ++ [binary_field(integer(I), integer(BitS), [])]);
abstract(T) ->
    erlang:error({badarg, T}).

abstract_list([T | Ts]) ->
    [abstract(T) | abstract_list(Ts)];
abstract_list([]) ->
    [].

%% This is entered when we might have a sequence of conses that might or
%% might not be a proper list, but which should not be considered as a
%% potential string, to avoid unnecessary checking. This also avoids
%% that a list like `[4711, 42, 10]' could be abstracted to represent
%% `[4711 | "*\n"]'.

abstract_tail(H1, [H2 | T]) ->
    %% Recall that `cons' does "intelligent" composition
    cons(abstract(H1), abstract_tail(H2, T));
abstract_tail(H, T) ->
    cons(abstract(H), abstract(T)).


%% =====================================================================
%% @doc Returns the Erlang term represented by a syntax tree. Evaluation
%% fails with reason `badarg' if `Node' does not
%% represent a literal term.
%%
%% Note: Currently, the set of syntax trees which have a concrete
%% representation is larger than the set of trees which can be built
%% using the function {@link abstract/1}. An abstract character
%% will be concretised as an integer, while {@link abstract/1} does
%% not at present yield an abstract character for any input. (Use the
%% {@link char/1} function to explicitly create an abstract
%% character.)
%%
%% Note: `arity_qualifier' nodes are recognized. This is to follow The
%% Erlang Parser when it comes to wild attributes: both {F, A} and F/A
%% are recognized, which makes it possible to turn wild attributes
%% into recognized attributes without at the same time making it
%% impossible to compile files using the new syntax with the old
%% version of the Erlang Compiler.
%%
%% @see abstract/1
%% @see is_literal/1
%% @see char/1

-doc """
Returns the Erlang term represented by a syntax tree. Evaluation fails with
reason `badarg` if `Node` does not represent a literal term.

Note: Currently, the set of syntax trees which have a concrete representation is
larger than the set of trees which can be built using the function `abstract/1`.
An abstract character will be concretised as an integer, while `abstract/1` does
not at present yield an abstract character for any input. (Use the `char/1`
function to explicitly create an abstract character.)

Note: `arity_qualifier` nodes are recognized. This is to follow The Erlang
Parser when it comes to wild attributes: both \{F, A\} and F/A are recognized,
which makes it possible to turn wild attributes into recognized attributes
without at the same time making it impossible to compile files using the new
syntax with the old version of the Erlang Compiler.

_See also: _`abstract/1`, `char/1`, `is_literal/1`.
""".
-spec concrete(syntaxTree()) -> term().

concrete(Node) ->
    case type(Node) of
	atom ->
	    atom_value(Node);
	integer ->
	    integer_value(Node);
	float ->
	    float_value(Node);
	char ->
	    char_value(Node);
	string ->
	    string_value(Node);
	nil ->
	    [];
	list ->
	    [concrete(list_head(Node))
	     | concrete(list_tail(Node))];
	tuple ->
	    list_to_tuple(concrete_list(tuple_elements(Node)));
	map_expr ->
	    As = [tuple([map_field_assoc_name(F),
			 map_field_assoc_value(F)]) || F <- map_expr_fields(Node)],
	    M0 = maps:from_list(concrete_list(As)),
	    case map_expr_argument(Node) of
		none  -> M0;
		Node0 -> maps:merge(concrete(Node0),M0)
	    end;
	binary ->
            Fs = [begin
                      B = binary_field_body(F),
                      {Body, Size} =
                          case type(B) of
                              size_qualifier ->
                                  {size_qualifier_body(B),
                                   size_qualifier_argument(B)};
                              _ ->
                                  {B, none}
                          end,
                      revert_binary_field(
                        binary_field(Body, Size, binary_field_types(F)))
                  end
                  || F <- binary_fields(Node)],
	    {value, B, _} =
		eval_bits:expr_grp(Fs, [],
				   fun(F, _) ->
					   {value, concrete(F), []}
				   end),
	    B;
        arity_qualifier ->
            A = erl_syntax:arity_qualifier_argument(Node),
            case erl_syntax:type(A) of
                integer ->
                    F = erl_syntax:arity_qualifier_body(Node),
                    case erl_syntax:type(F) of
                        atom ->
                            {F, A};
                        _ ->
                            erlang:error({badarg, Node})
                    end;
                _ ->
                    erlang:error({badarg, Node})
            end;
        _ ->
	    erlang:error({badarg, Node})
    end.

concrete_list([E | Es]) ->
    [concrete(E) | concrete_list(Es)];
concrete_list([]) ->
    [].


%% =====================================================================
%% @doc Returns `true' if `Node' represents a
%% literal term, otherwise `false'. This function returns
%% `true' if and only if the value of
%% `concrete(Node)' is defined.
%%
%% @see abstract/1
%% @see concrete/1

-doc """
Returns `true` if `Node` represents a literal term, otherwise `false`. This
function returns `true` if and only if the value of
[`concrete(Node)`](`concrete/1`) is defined.

_See also: _`abstract/1`, `concrete/1`.
""".
-spec is_literal(syntaxTree()) -> boolean().

is_literal(T) ->
    case type(T) of
	atom ->
	    true;
	integer ->
	    true;
	float ->
	    true;
	char->
	    true;
	string ->
	    true;
	nil ->
	    true;
	list ->
	    is_literal(list_head(T)) andalso is_literal(list_tail(T));
	tuple ->
	    lists:all(fun is_literal/1, tuple_elements(T));
	map_expr ->
	    case map_expr_argument(T) of
		none -> true;
		Arg  -> is_literal(Arg)
	    end andalso lists:all(fun is_literal_map_field/1, map_expr_fields(T));
	binary ->
	    lists:all(fun is_literal_binary_field/1, binary_fields(T));
	_ ->
	    false
    end.

is_literal_binary_field(F) ->
    case binary_field_types(F) of
	[] -> B = binary_field_body(F),
              case type(B) of
                  size_qualifier ->
                      is_literal(size_qualifier_body(B)) andalso
                          is_literal(size_qualifier_argument(B));
                  _ ->
                      is_literal(B)
              end;
	_  -> false
    end.

is_literal_map_field(F) ->
    case type(F) of
	map_field_assoc ->
	    is_literal(map_field_assoc_name(F)) andalso
	    is_literal(map_field_assoc_value(F));
	map_field_exact ->
	    false
    end.

%% =====================================================================
%% @doc Returns an `erl_parse'-compatible representation of a
%% syntax tree, if possible. If `Tree' represents a
%% well-formed Erlang program or expression, the conversion should work
%% without problems. Typically, {@link is_tree/1} yields
%% `true' if conversion failed (i.e., the result is still an
%% abstract syntax tree), and `false' otherwise.
%%
%% The {@link is_tree/1} test is not completely foolproof. For a
%% few special node types (e.g. `arity_qualifier'), if such a
%% node occurs in a context where it is not expected, it will be left
%% unchanged as a non-reverted subtree of the result. This can only
%% happen if `Tree' does not actually represent legal Erlang
%% code.
%%
%% @see revert_forms/1
%% @see //stdlib/erl_parse

-doc """
Returns an `erl_parse`\-compatible representation of a syntax tree, if possible.
If `Tree` represents a well-formed Erlang program or expression, the conversion
should work without problems. Typically, `is_tree/1` yields `true` if conversion
failed (i.e., the result is still an abstract syntax tree), and `false`
otherwise.

The `is_tree/1` test is not completely foolproof. For a few special node types
(e.g. `arity_qualifier`), if such a node occurs in a context where it is not
expected, it will be left unchanged as a non-reverted subtree of the result.
This can only happen if `Tree` does not actually represent legal Erlang code.

_See also: _[//stdlib/erl_parse](`m:erl_parse`), `revert_forms/1`.
""".
-spec revert(syntaxTree()) -> syntaxTree().

revert(Node) ->
    case is_leaf(Node) of
		true ->
		    revert_root(Node);
		false ->
		    %% First revert the subtrees, where possible.
		    %% (Sometimes, subtrees cannot be reverted out of
		    %% context, and the real work will be done when the
		    %% parent node is reverted.)
		    Gs = [[revert(X) || X <- L] || L <- subtrees(Node)],

		    %% Then reconstruct the node from the reverted
		    %% parts, and revert the node itself.
		    Node1 = update_tree(Node, Gs),
		    revert_root(Node1)
    end.

%% Note: The concept of "compatible root node" is not strictly defined.
%% At a minimum, if `make_tree' is used to compose a node `T' from
%% subtrees that are all completely backwards compatible, then the
%% result of `revert_root(T)' should also be completely backwards
%% compatible.

revert_root(Node) ->
    case type(Node) of
        annotated_type ->
            revert_annotated_type(Node);
	application ->
	    revert_application(Node);
	atom ->
	    revert_atom(Node);
	attribute ->
	    revert_attribute(Node);
	binary ->
	    revert_binary(Node);
        binary_comp ->
	    revert_binary_comp(Node);
	binary_field ->
	    revert_binary_field(Node);
        binary_generator ->
	    revert_binary_generator(Node);
        bitstring_type ->
            revert_bitstring_type(Node);
	block_expr ->
	    revert_block_expr(Node);
        'case_expr' ->                          %Quoted to help Emacs.
	    revert_case_expr(Node);
        'catch_expr' ->                         %Quoted to help Emacs.
	    revert_catch_expr(Node);
	char ->
	    revert_char(Node);
	clause ->
	    revert_clause(Node);
        constrained_function_type ->
            revert_constrained_function_type(Node);
        constraint ->
            revert_constraint(Node);
        else_expr ->
            revert_else_expr(Node);
	eof_marker ->
	    revert_eof_marker(Node);
	error_marker ->
	    revert_error_marker(Node);
	float ->
	    revert_float(Node);
	fun_expr ->
	    revert_fun_expr(Node);
        fun_type ->
            revert_fun_type(Node);
	function ->
	    revert_function(Node);
        function_type ->
            revert_function_type(Node);
	generator ->
	    revert_generator(Node);
	if_expr ->
	    revert_if_expr(Node);
	implicit_fun ->
	    revert_implicit_fun(Node);
	infix_expr ->
	    revert_infix_expr(Node);
	integer ->
	    revert_integer(Node);
        integer_range_type ->
            revert_integer_range_type(Node);
	list ->
	    revert_list(Node);
	list_comp ->
	    revert_list_comp(Node);
        map_comp ->
	    revert_map_comp(Node);
        map_expr ->
            revert_map_expr(Node);
        map_field_assoc ->
            revert_map_field_assoc(Node);
        map_field_exact ->
            revert_map_field_exact(Node);
        map_generator ->
            revert_map_generator(Node);
        map_type ->
            revert_map_type(Node);
        map_type_assoc ->
            revert_map_type_assoc(Node);
        map_type_exact ->
            revert_map_type_exact(Node);
	match_expr ->
	    revert_match_expr(Node);
        maybe_match_expr ->
            revert_maybe_match_expr(Node);
        maybe_expr ->
            revert_maybe_expr(Node);
	module_qualifier ->
	    revert_module_qualifier(Node);
	named_fun_expr ->
	    revert_named_fun_expr(Node);
	nil ->
	    revert_nil(Node);
	parentheses ->
	    revert_parentheses(Node);
	prefix_expr ->
	    revert_prefix_expr(Node);
	receive_expr ->
	    revert_receive_expr(Node);
	record_access ->
	    revert_record_access(Node);
	record_expr ->
	    revert_record_expr(Node);
	record_index_expr ->
	    revert_record_index_expr(Node);
        record_type ->
            revert_record_type(Node);
        record_type_field ->
            revert_record_type_field(Node);
        type_application ->
            revert_type_application(Node);
        type_union ->
            revert_type_union(Node);
	string ->
	    revert_string(Node);
	try_expr ->
	    revert_try_expr(Node);
	tuple ->
	    revert_tuple(Node);
        tuple_type ->
            revert_tuple_type(Node);
	underscore ->
	    revert_underscore(Node);
        user_type_application ->
            revert_user_type_application(Node);
	variable ->
	    revert_variable(Node);
	warning_marker ->
	    revert_warning_marker(Node);
	_ ->
	    %% Non-revertible new-form node
	    Node
    end.


%% =====================================================================
%% @doc Reverts a sequence of Erlang source code forms. The sequence can
%% be given either as a `form_list' syntax tree (possibly
%% nested), or as a list of "program form" syntax trees. If successful,
%% the corresponding flat list of `erl_parse'-compatible
%% syntax trees is returned (see {@link revert/1}). If some program
%% form could not be reverted, `{error, Form}' is thrown.
%% Standalone comments in the form sequence are discarded.
%%
%% @see revert/1
%% @see form_list/1
%% @see is_form/1

-type forms() :: syntaxTree() | [syntaxTree()].

-doc """
Reverts a sequence of Erlang source code forms. The sequence can be given either
as a `form_list` syntax tree (possibly nested), or as a list of "program form"
syntax trees. If successful, the corresponding flat list of
`erl_parse`\-compatible syntax trees is returned (see `revert/1`). If some
program form could not be reverted, `{error, Form}` is thrown. Standalone
comments in the form sequence are discarded.

_See also: _`form_list/1`, `is_form/1`, `revert/1`.
""".
-spec revert_forms(forms()) -> [erl_parse()].

revert_forms(Forms) when is_list(Forms) ->
    revert_forms(form_list(Forms));
revert_forms(T) ->
    case type(T) of
	form_list ->
	    T1 = flatten_form_list(T),
	    case catch {ok, revert_forms_1(form_list_elements(T1))} of
		{ok, Fs} ->
		    Fs;
		{error, _} = Error ->
		    erlang:error(Error);
		{'EXIT', R} ->
		    exit(R);
		R ->
		    throw(R)
	    end;
	_ ->
	    erlang:error({badarg, T})
    end.

revert_forms_1([T | Ts]) ->
    case type(T) of
	comment ->
	    revert_forms_1(Ts);
	_ ->
	    T1 = revert(T),
	    case is_tree(T1) of
		true ->
		    throw({error, T1});
		false ->
		    [T1 | revert_forms_1(Ts)]
	    end
    end;
revert_forms_1([]) ->
    [].


%% =====================================================================
%% @doc Returns the grouped list of all subtrees of a syntax tree. If
%% `Node' is a leaf node (see {@link is_leaf/1}), this
%% is the empty list, otherwise the result is always a nonempty list,
%% containing the lists of subtrees of `Node', in
%% left-to-right order as they occur in the printed program text, and
%% grouped by category. Often, each group contains only a single
%% subtree.
%%
%% Depending on the type of `Node', the size of some
%% groups may be variable (e.g., the group consisting of all the
%% elements of a tuple), while others always contain the same number of
%% elements - usually exactly one (e.g., the group containing the
%% argument expression of a case-expression). Note, however, that the
%% exact structure of the returned list (for a given node type) should
%% in general not be depended upon, since it might be subject to change
%% without notice.
%%
%% The function {@link subtrees/1} and the constructor functions
%% {@link make_tree/2} and {@link update_tree/2} can be a
%% great help if one wants to traverse a syntax tree, visiting all its
%% subtrees, but treat nodes of the tree in a uniform way in most or all
%% cases. Using these functions makes this simple, and also assures that
%% your code is not overly sensitive to extensions of the syntax tree
%% data type, because any node types not explicitly handled by your code
%% can be left to a default case.
%%
%% For example:
%% ```postorder(F, Tree) ->
%%       F(case subtrees(Tree) of
%%           [] -> Tree;
%%           List -> update_tree(Tree,
%%                               [[postorder(F, Subtree)
%%                                 || Subtree &lt;- Group]
%%                                || Group &lt;- List])
%%         end).'''
%% maps the function `F' on `Tree' and all its
%% subtrees, doing a post-order traversal of the syntax tree. (Note the
%% use of {@link update_tree/2} to preserve node attributes.) For a
%% simple function like:
%% ```f(Node) ->
%%       case type(Node) of
%%           atom -> atom("a_" ++ atom_name(Node));
%%           _ -> Node
%%       end.'''
%% the call `postorder(fun f/1, Tree)' will yield a new
%% representation of `Tree' in which all atom names have been
%% extended with the prefix "a_", but nothing else (including comments,
%% annotations and line numbers) has been changed.
%%
%% @see make_tree/2
%% @see type/1
%% @see is_leaf/1
%% @see copy_attrs/2

-doc """
Returns the grouped list of all subtrees of a syntax tree. If `Node` is a leaf
node (see `is_leaf/1`), this is the empty list, otherwise the result is always a
nonempty list, containing the lists of subtrees of `Node`, in left-to-right
order as they occur in the printed program text, and grouped by category. Often,
each group contains only a single subtree.

Depending on the type of `Node`, the size of some groups may be variable (e.g.,
the group consisting of all the elements of a tuple), while others always
contain the same number of elements - usually exactly one (e.g., the group
containing the argument expression of a case-expression). Note, however, that
the exact structure of the returned list (for a given node type) should in
general not be depended upon, since it might be subject to change without
notice.

The function `subtrees/1` and the constructor functions `make_tree/2` and
`update_tree/2` can be a great help if one wants to traverse a syntax tree,
visiting all its subtrees, but treat nodes of the tree in a uniform way in most
or all cases. Using these functions makes this simple, and also assures that
your code is not overly sensitive to extensions of the syntax tree data type,
because any node types not explicitly handled by your code can be left to a
default case.

For example:

```text
     postorder(F, Tree) ->
        F(case subtrees(Tree) of
            [] -> Tree;
            List -> update_tree(Tree,
                                [[postorder(F, Subtree)
                                  || Subtree &lt;- Group]
                                 || Group &lt;- List])
          end).
```

maps the function `F` on `Tree` and all its subtrees, doing a post-order
traversal of the syntax tree. (Note the use of `update_tree/2` to preserve node
attributes.) For a simple function like:

```text
     f(Node) ->
        case type(Node) of
            atom -> atom("a_" ++ atom_name(Node));
            _ -> Node
        end.
```

the call `postorder(fun f/1, Tree)` will yield a new representation of `Tree` in
which all atom names have been extended with the prefix "a\_", but nothing else
(including comments, annotations and line numbers) has been changed.

_See also: _`copy_attrs/2`, `is_leaf/1`, `make_tree/2`, `type/1`.
""".
-spec subtrees(syntaxTree()) -> [[syntaxTree()]].

subtrees(T) ->
    case is_leaf(T) of
	true ->
	    [];
	false ->
	    case type(T) of
                annotated_type ->
                    [[annotated_type_name(T)],
                     [annotated_type_body(T)]];
		application ->
		    [[application_operator(T)],
		     application_arguments(T)];
		arity_qualifier ->
		    [[arity_qualifier_body(T)],
		     [arity_qualifier_argument(T)]];
		attribute ->
		    case attribute_arguments(T) of
			none ->
			    [[attribute_name(T)]];
			As ->
			    [[attribute_name(T)], As]
		    end;
		binary ->
		    [binary_fields(T)];
		binary_comp ->
		    [[binary_comp_template(T)], binary_comp_body(T)];
                binary_field ->
		    case binary_field_types(T) of
			[] ->
			    [[binary_field_body(T)]];
			Ts ->
			    [[binary_field_body(T)],
			     Ts]
		    end;
	        binary_generator ->
		    [[binary_generator_pattern(T)], 
                     [binary_generator_body(T)]];
                bitstring_type ->
                    [[bitstring_type_m(T)],
                     [bitstring_type_n(T)]];
		block_expr ->
		    [block_expr_body(T)];
		case_expr ->
		    [[case_expr_argument(T)],
		     case_expr_clauses(T)];
                'catch_expr' ->                 %Quoted to help Emacs.
		    [[catch_expr_body(T)]];
		class_qualifier ->
                    [[class_qualifier_argument(T)],
                     [class_qualifier_body(T)],
                     [class_qualifier_stacktrace(T)]];
		clause ->
		    case clause_guard(T) of
			none ->
			    [clause_patterns(T), clause_body(T)];
			G ->
			    [clause_patterns(T), [G],
			     clause_body(T)]
		    end;
		conjunction ->
		    [conjunction_body(T)];
                constrained_function_type ->
                    C = constrained_function_type_argument(T),
                    [[constrained_function_type_body(T)],
                     conjunction_body(C)];
                constraint ->
                    [[constraint_argument(T)],
                     constraint_body(T)];
		disjunction ->
		    [disjunction_body(T)];
		else_expr ->
                    [else_expr_clauses(T)];
		form_list ->
		    [form_list_elements(T)];
		fun_expr ->
		    [fun_expr_clauses(T)];
                fun_type ->
                    [];
		function ->
		    [[function_name(T)], function_clauses(T)];
                function_type ->
                    case function_type_arguments(T) of
                        any_arity ->
                            [[function_type_return(T)]];
                        As ->
                            [As,[function_type_return(T)]]
                    end;
		generator ->
		    [[generator_pattern(T)], [generator_body(T)]];
		if_expr ->
		    [if_expr_clauses(T)];
		implicit_fun ->
		    [[implicit_fun_name(T)]];
		infix_expr ->
		    [[infix_expr_left(T)],
		     [infix_expr_operator(T)],
		     [infix_expr_right(T)]];
                integer_range_type ->
                    [[integer_range_type_low(T)],
                     [integer_range_type_high(T)]];
		list ->
		    case list_suffix(T) of
			none ->
			    [list_prefix(T)];
			S ->
			    [list_prefix(T), [S]]
		    end;
		list_comp ->
		    [[list_comp_template(T)], list_comp_body(T)];
		macro ->
		    case macro_arguments(T) of
			none ->
			    [[macro_name(T)]];
			As ->
			    [[macro_name(T)], As]
		    end;
                map_comp ->
                    [[map_comp_template(T)], map_comp_body(T)];
                map_expr ->
                    case map_expr_argument(T) of
                        none ->
                            [map_expr_fields(T)];
                        V ->
                            [[V], map_expr_fields(T)]
                    end;
                map_field_assoc ->
                    [[map_field_assoc_name(T)],
                     [map_field_assoc_value(T)]];
                map_field_exact ->
                    [[map_field_exact_name(T)],
                     [map_field_exact_value(T)]];
	        map_generator ->
                    [[map_generator_pattern(T)],
                     [map_generator_body(T)]];
                map_type ->
                    [map_type_fields(T)];
                map_type_assoc ->
                    [[map_type_assoc_name(T)],
                     [map_type_assoc_value(T)]];
                map_type_exact ->
                    [[map_type_exact_name(T)],
                     [map_type_exact_value(T)]];
		match_expr ->
		    [[match_expr_pattern(T)],
		     [match_expr_body(T)]];
                maybe_expr ->
                    case maybe_expr_else(T) of
                        none ->
                            [maybe_expr_body(T)];
                        E ->
                            [maybe_expr_body(T),
                             [E]]
                    end;
                maybe_match_expr ->
                    [[maybe_match_expr_pattern(T)],
                     [maybe_match_expr_body(T)]];
		module_qualifier ->
		    [[module_qualifier_argument(T)],
		     [module_qualifier_body(T)]];
		named_fun_expr ->
			[[named_fun_expr_name(T)],
			 named_fun_expr_clauses(T)];
		parentheses ->
		    [[parentheses_body(T)]];
		prefix_expr ->
		    [[prefix_expr_operator(T)],
		     [prefix_expr_argument(T)]];
		receive_expr ->
		    case receive_expr_timeout(T) of
			none ->
			    [receive_expr_clauses(T)];
			E ->
			    [receive_expr_clauses(T),
			     [E],
			     receive_expr_action(T)]
		    end;
		record_access ->
                    [[record_access_argument(T)],
                     [record_access_type(T)],
                     [record_access_field(T)]];
		record_expr ->
		    case record_expr_argument(T) of
			none ->
			    [[record_expr_type(T)],
			     record_expr_fields(T)];
			V ->
			    [[V],
			     [record_expr_type(T)],
			     record_expr_fields(T)]
		    end;
		record_field ->
		    case record_field_value(T) of
			none ->
			    [[record_field_name(T)]];
			V ->
			    [[record_field_name(T)], [V]]
		    end;
		record_index_expr ->
		    [[record_index_expr_type(T)],
		     [record_index_expr_field(T)]];
                record_type ->
                    [[record_type_name(T)],
                     record_type_fields(T)];
                record_type_field ->
                    [[record_type_field_name(T)],
                     [record_type_field_type(T)]];
		size_qualifier ->
		    [[size_qualifier_body(T)],
		     [size_qualifier_argument(T)]];
		try_expr ->
		    [try_expr_body(T),
		     try_expr_clauses(T),
		     try_expr_handlers(T),
		     try_expr_after(T)];
		tuple ->
		    [tuple_elements(T)];
                tuple_type ->
                    [tuple_type_elements(T)];
                type_application ->
                    [[type_application_name(T)],
                     type_application_arguments(T)];
                type_union ->
                    [type_union_types(T)];
		typed_record_field ->
                    [[typed_record_field_body(T)],
                     [typed_record_field_type(T)]];
                user_type_application ->
                    [[user_type_application_name(T)],
                     user_type_application_arguments(T)]
	    end
    end.


%% =====================================================================
%% @doc Creates a syntax tree with the same type and attributes as the
%% given tree. This is equivalent to `copy_attrs(Node,
%% make_tree(type(Node), Groups))'.
%%
%% @see make_tree/2
%% @see copy_attrs/2
%% @see type/1

-doc """
Creates a syntax tree with the same type and attributes as the given tree. This
is equivalent to
[`copy_attrs(Node, make_tree(type(Node), Groups))`](`copy_attrs/2`).

_See also: _`copy_attrs/2`, `make_tree/2`, `type/1`.
""".
-spec update_tree(syntaxTree(), [[syntaxTree()]]) -> syntaxTree().

update_tree(Node, Groups) ->
    copy_attrs(Node, make_tree(type(Node), Groups)).


%% =====================================================================
%% @doc Creates a syntax tree with the given type and subtrees.
%% `Type' must be a node type name (see {@link type/1})
%% that does not denote a leaf node type (see {@link is_leaf/1}).
%% `Groups' must be a <em>nonempty</em> list of groups of
%% syntax trees, representing the subtrees of a node of the given type,
%% in left-to-right order as they would occur in the printed program
%% text, grouped by category as done by {@link subtrees/1}.
%%
%% The result of `copy_attrs(Node, make_tree(type(Node),
%% subtrees(Node)))' (see {@link update_tree/2}) represents
%% the same source code text as the original `Node', assuming
%% that `subtrees(Node)' yields a nonempty list. However, it
%% does not necessarily have the same data representation as
%% `Node'.
%%
%% @see update_tree/2
%% @see subtrees/1
%% @see type/1
%% @see is_leaf/1
%% @see copy_attrs/2

-doc """
Creates a syntax tree with the given type and subtrees. `Type` must be a node
type name (see `type/1`) that does not denote a leaf node type (see
`is_leaf/1`). `Groups` must be a _nonempty_ list of groups of syntax trees,
representing the subtrees of a node of the given type, in left-to-right order as
they would occur in the printed program text, grouped by category as done by
`subtrees/1`.

The result of
[`copy_attrs(Node, make_tree(type(Node), subtrees(Node)))`](`copy_attrs/2`) (see
`update_tree/2`) represents the same source code text as the original `Node`,
assuming that [`subtrees(Node)`](`subtrees/1`) yields a nonempty list. However,
it does not necessarily have the same data representation as `Node`.

_See also: _`copy_attrs/2`, `is_leaf/1`, `subtrees/1`, `type/1`,
`update_tree/2`.
""".
-spec make_tree(atom(), [[syntaxTree()]]) -> syntaxTree().

make_tree(annotated_type, [[N], [T]]) -> annotated_type(N, T);
make_tree(application, [[F], A]) -> application(F, A);
make_tree(arity_qualifier, [[N], [A]]) -> arity_qualifier(N, A);
make_tree(attribute, [[N]]) -> attribute(N);
make_tree(attribute, [[N], A]) -> attribute(N, A);
make_tree(binary, [Fs]) -> binary(Fs);
make_tree(binary_comp, [[T], B]) -> binary_comp(T, B);
make_tree(binary_field, [[B]]) -> binary_field(B);
make_tree(binary_field, [[B], Ts]) -> binary_field(B, Ts);
make_tree(binary_generator, [[P], [E]]) -> binary_generator(P, E);
make_tree(bitstring_type, [[M], [N]]) -> bitstring_type(M, N);
make_tree(block_expr, [B]) -> block_expr(B);
make_tree(case_expr, [[A], C]) -> case_expr(A, C);
make_tree(catch_expr, [[B]]) -> catch_expr(B);
make_tree(class_qualifier, [[A], [B]]) -> class_qualifier(A, B);
make_tree(class_qualifier, [[A], [B], [C]]) -> class_qualifier(A, B, C);
make_tree(clause, [P, B]) -> clause(P, none, B);
make_tree(clause, [P, [G], B]) -> clause(P, G, B);
make_tree(conjunction, [E]) -> conjunction(E);
make_tree(constrained_function_type, [[F],C]) ->
    constrained_function_type(F, C);
make_tree(constraint, [[N], Ts]) -> constraint(N, Ts);
make_tree(disjunction, [E]) -> disjunction(E);
make_tree(else_expr, [E]) -> else_expr(E);
make_tree(form_list, [E]) -> form_list(E);
make_tree(fun_expr, [C]) -> fun_expr(C);
make_tree(function, [[N], C]) -> function(N, C);
make_tree(function_type, [[T]]) -> function_type(T);
make_tree(function_type, [A,[T]]) -> function_type(A, T);
make_tree(generator, [[P], [E]]) -> generator(P, E);
make_tree(if_expr, [C]) -> if_expr(C);
make_tree(implicit_fun, [[N]]) -> implicit_fun(N);
make_tree(infix_expr, [[L], [F], [R]]) -> infix_expr(L, F, R);
make_tree(integer_range_type, [[L],[H]]) -> integer_range_type(L, H);
make_tree(list, [P]) -> list(P);
make_tree(list, [P, [S]]) -> list(P, S);
make_tree(list_comp, [[T], B]) -> list_comp(T, B);
make_tree(macro, [[N]]) -> macro(N);
make_tree(macro, [[N], A]) -> macro(N, A);
make_tree(map_comp, [[T], B]) -> map_comp(T, B);
make_tree(map_expr, [Fs]) -> map_expr(Fs);
make_tree(map_expr, [[E], Fs]) -> map_expr(E, Fs);
make_tree(map_field_assoc, [[K], [V]]) -> map_field_assoc(K, V);
make_tree(map_field_exact, [[K], [V]]) -> map_field_exact(K, V);
make_tree(map_generator, [[P], [E]]) -> map_generator(P, E);
make_tree(map_type, [Fs]) -> map_type(Fs);
make_tree(map_type_assoc, [[N],[V]]) -> map_type_assoc(N, V);
make_tree(map_type_exact, [[N],[V]]) -> map_type_exact(N, V);
make_tree(match_expr, [[P], [E]]) -> match_expr(P, E);
make_tree(maybe_expr, [Body]) -> maybe_expr(Body);
make_tree(maybe_expr, [Body, [Else]]) -> maybe_expr(Body, Else);
make_tree(maybe_match_expr, [[P], [E]]) -> maybe_match_expr(P, E);
make_tree(named_fun_expr, [[N], C]) -> named_fun_expr(N, C);
make_tree(module_qualifier, [[M], [N]]) -> module_qualifier(M, N);
make_tree(parentheses, [[E]]) -> parentheses(E);
make_tree(prefix_expr, [[F], [A]]) -> prefix_expr(F, A);
make_tree(receive_expr, [C]) -> receive_expr(C);
make_tree(receive_expr, [C, [E], A]) -> receive_expr(C, E, A);
make_tree(record_access, [[E], [T], [F]]) ->
    record_access(E, T, F);
make_tree(record_expr, [[T], F]) -> record_expr(T, F);
make_tree(record_expr, [[E], [T], F]) -> record_expr(E, T, F);
make_tree(record_field, [[N]]) -> record_field(N);
make_tree(record_field, [[N], [E]]) -> record_field(N, E);
make_tree(record_index_expr, [[T], [F]]) ->
    record_index_expr(T, F);
make_tree(record_type, [[N],Fs]) -> record_type(N, Fs);
make_tree(record_type_field, [[N],[T]]) -> record_type_field(N, T);
make_tree(size_qualifier, [[N], [A]]) -> size_qualifier(N, A);
make_tree(try_expr, [B, C, H, A]) -> try_expr(B, C, H, A);
make_tree(tuple, [E]) -> tuple(E);
make_tree(tuple_type, [Es]) -> tuple_type(Es);
make_tree(type_application, [[N], Ts]) -> type_application(N, Ts);
make_tree(type_union, [Es]) -> type_union(Es);
make_tree(typed_record_field, [[F],[T]]) -> typed_record_field(F, T);
make_tree(user_type_application, [[N], Ts]) -> user_type_application(N, Ts).


%% =====================================================================
%% @doc Creates a meta-representation of a syntax tree. The result
%% represents an Erlang expression "<code><em>MetaTree</em></code>"
%% which, if evaluated, will yield a new syntax tree representing the
%% same source code text as `Tree' (although the actual data
%% representation may be different). The expression represented by
%% `MetaTree' is <em>implementation independent</em> with
%% regard to the data structures used by the abstract syntax tree
%% implementation. Comments attached to nodes of `Tree' will
%% be preserved, but other attributes are lost.
%%
%% Any node in `Tree' whose node type is
%% `variable' (see {@link type/1}), and whose list of
%% annotations (see {@link get_ann/1}) contains the atom
%% `meta_var', will remain unchanged in the resulting tree,
%% except that exactly one occurrence of `meta_var' is
%% removed from its annotation list.
%%
%% The main use of the function `meta/1' is to transform a
%% data structure `Tree', which represents a piece of program
%% code, into a form that is <em>representation independent when
%% printed</em>. E.g., suppose `Tree' represents a variable
%% named "V". Then (assuming a function `print/1' for
%% printing syntax trees), evaluating `print(abstract(Tree))'
%% - simply using {@link abstract/1} to map the actual data
%% structure onto a syntax tree representation - would output a string
%% that might look something like "`{tree, variable, ..., "V",
%% ...}'", which is obviously dependent on the implementation of
%% the abstract syntax trees. This could e.g. be useful for caching a
%% syntax tree in a file. However, in some situations like in a program
%% generator generator (with two "generator"), it may be unacceptable.
%% Using `print(meta(Tree))' instead would output a
%% <em>representation independent</em> syntax tree generating
%% expression; in the above case, something like
%% "`erl_syntax:variable("V")'".
%%
%% @see abstract/1
%% @see type/1
%% @see get_ann/1

-doc """
Creates a meta-representation of a syntax tree. The result represents an Erlang
expression "`*MetaTree*`" which, if evaluated, will yield a new syntax tree
representing the same source code text as `Tree` (although the actual data
representation may be different). The expression represented by `MetaTree` is
_implementation independent_ with regard to the data structures used by the
abstract syntax tree implementation. Comments attached to nodes of `Tree` will
be preserved, but other attributes are lost.

Any node in `Tree` whose node type is `variable` (see `type/1`), and whose list
of annotations (see `get_ann/1`) contains the atom `meta_var`, will remain
unchanged in the resulting tree, except that exactly one occurrence of
`meta_var` is removed from its annotation list.

The main use of the function [`meta/1`](`meta/1`) is to transform a data
structure `Tree`, which represents a piece of program code, into a form that is
_representation independent when printed_. E.g., suppose `Tree` represents a
variable named "V". Then (assuming a function `print/1` for printing syntax
trees), evaluating `print(abstract(Tree))` \- simply using `abstract/1` to map
the actual data structure onto a syntax tree representation - would output a
string that might look something like "`{tree, variable, ..., "V", ...}`", which
is obviously dependent on the implementation of the abstract syntax trees. This
could e.g. be useful for caching a syntax tree in a file. However, in some
situations like in a program generator generator (with two "generator"), it may
be unacceptable. Using `print(meta(Tree))` instead would output a
_representation independent_ syntax tree generating expression; in the above
case, something like "`erl_syntax:variable("V")`".

_See also: _`abstract/1`, `get_ann/1`, `type/1`.
""".
-spec meta(syntaxTree()) -> syntaxTree().

meta(T) ->
    %% First of all we check for metavariables:
    case type(T) of
	variable ->
	    case lists:member(meta_var, get_ann(T)) of
		false ->
		    meta_precomment(T);
		true ->
		    %% A meta-variable: remove the first found
		    %% `meta_var' annotation, but otherwise leave
		    %% the node unchanged.
		    set_ann(T, lists:delete(meta_var, get_ann(T)))
	    end;
	_ ->
	    case has_comments(T) of
		true ->
		    meta_precomment(T);
		false ->
		    meta_1(T)
	    end
    end.

meta_precomment(T) ->
    case get_precomments(T) of
	[] ->
	    meta_postcomment(T);
	Cs ->
	    meta_call(set_precomments,
		      [meta_postcomment(T), list(meta_list(Cs))])
    end.

meta_postcomment(T) ->
    case get_postcomments(T) of
	[] ->
	    meta_0(T);
	Cs ->
	    meta_call(set_postcomments,
		      [meta_0(T), list(meta_list(Cs))])
    end.

meta_0(T) ->
    meta_1(remove_comments(T)).

meta_1(T) ->
    %% First handle leaf nodes and other common cases, in order to
    %% generate compact code.
    case type(T) of
	atom ->
	    meta_call(atom, [T]);
	char ->
	    meta_call(char, [T]);
	comment ->
	    meta_call(comment, [list([string(S)
				      || S <- comment_text(T)])]);
	eof_marker ->
	    meta_call(eof_marker, []);
	error_marker ->
	    meta_call(error_marker,
		      [abstract(error_marker_info(T))]);
	float ->
	    meta_call(float, [T]);
	integer ->
	    meta_call(integer, [T]);
	nil ->
	    meta_call(nil, []);
	operator ->
	    meta_call(operator, [atom(operator_name(T))]);
	string ->
	    meta_call(string, [T]);
	text ->
	    meta_call(text, [string(text_string(T))]);
	underscore ->
	    meta_call(underscore, []);
	variable ->
	    meta_call(variable, [string(atom_to_list(variable_name(T)))]);
	warning_marker ->
	    meta_call(warning_marker,
		      [abstract(warning_marker_info(T))]);
	list ->
	    case list_suffix(T) of
		none ->
		    meta_call(list,
			      [list(meta_list(list_prefix(T)))]);
		S ->
		    meta_call(list,
			      [list(meta_list(list_prefix(T))),
			       meta(S)])
	    end;
	tuple ->
	    meta_call(tuple,
		      [list(meta_list(tuple_elements(T)))]);
	Type ->
	    %% All remaining cases are handled using `subtrees'
	    %% and `make_tree' to decompose and reassemble the
	    %% nodes. More cases could of course be handled
	    %% directly to get a more compact output, but I can't
	    %% be bothered right now.
	    meta_call(make_tree,
		      [abstract(Type),
		       meta_subtrees(subtrees(T))])
    end.

meta_list([T | Ts]) ->
    [meta(T) | meta_list(Ts)];
meta_list([]) ->
    [].

meta_subtrees(Gs) ->
    list([list([meta(T)
		|| T <- G])
	  || G <- Gs]).

meta_call(F, As) ->
    application(atom(?MODULE), atom(F), As).


%% =====================================================================
%% Functions for abstraction of the syntax tree representation; may be
%% used externally, but not intended for the normal user.
%% =====================================================================


%% =====================================================================
%% @equiv tree(Type, [])

-doc "Equivalent to [tree(Type, [])](`tree/2`).".
-spec tree(atom()) -> tree().

tree(Type) ->
    tree(Type, []).

%% =====================================================================
%% @doc <em>For special purposes only</em>. Creates an abstract syntax
%% tree node with type tag `Type' and associated data
%% `Data'.
%%
%% This function and the related {@link is_tree/1} and
%% {@link data/1} provide a uniform way to extend the set of
%% `erl_parse' node types. The associated data is any term,
%% whose format may depend on the type tag.
%%
%% === Notes: ===
%% <ul>
%%  <li>Any nodes created outside of this module must have type tags
%%      distinct from those currently defined by this module; see
%%      {@link type/1} for a complete list.</li>
%%  <li>The type tag of a syntax tree node may also be used
%%      as a primary tag by the `erl_parse' representation;
%%      in that case, the selector functions for that node type
%%      <em>must</em> handle both the abstract syntax tree and the
%%      `erl_parse' form. The function `type(T)'
%%      should return the correct type tag regardless of the
%%      representation of `T', so that the user sees no
%%      difference between `erl_syntax' and
%%      `erl_parse' nodes.</li>
%% </ul>
%%
%% @see is_tree/1
%% @see data/1
%% @see type/1

-doc """
_For special purposes only_. Creates an abstract syntax tree node with type tag
`Type` and associated data `Data`.

This function and the related `is_tree/1` and `data/1` provide a uniform way to
extend the set of `erl_parse` node types. The associated data is any term, whose
format may depend on the type tag.

#### Notes:

- Any nodes created outside of this module must have type tags distinct from
  those currently defined by this module; see `type/1` for a complete list.
- The type tag of a syntax tree node may also be used as a primary tag by the
  `erl_parse` representation; in that case, the selector functions for that node
  type _must_ handle both the abstract syntax tree and the `erl_parse` form. The
  function [`type(T)`](`type/1`) should return the correct type tag regardless
  of the representation of `T`, so that the user sees no difference between
  `erl_syntax` and `erl_parse` nodes.

_See also: _`data/1`, `is_tree/1`, `type/1`.
""".
-spec tree(atom(), term()) -> tree().

tree(Type, Data) ->
    #tree{type = Type, data = Data}.


%% =====================================================================
%% @doc <em>For special purposes only</em>. Returns `true' if
%% `Tree' is an abstract syntax tree and `false'
%% otherwise.
%%
%% <em>Note</em>: this function yields `false' for all
%% "old-style" `erl_parse'-compatible "parse trees".
%%
%% @see tree/2

-doc """
_For special purposes only_. Returns `true` if `Tree` is an abstract syntax tree
and `false` otherwise.

_Note_: this function yields `false` for all "old-style" `erl_parse`\-compatible
"parse trees".

_See also: _`tree/2`.
""".
-spec is_tree(syntaxTree()) -> boolean().

is_tree(#tree{}) ->
    true;
is_tree(_) ->
    false.


%% =====================================================================
%% @doc <em>For special purposes only</em>. Returns the associated data
%% of a syntax tree node. Evaluation fails with reason
%% `badarg' if `is_tree(Node)' does not yield
%% `true'.
%%
%% @see tree/2

-doc """
_For special purposes only_. Returns the associated data of a syntax tree node.
Evaluation fails with reason `badarg` if [`is_tree(Node)`](`is_tree/1`) does not
yield `true`.

_See also: _`tree/2`.
""".
-spec data(syntaxTree()) -> term().

data(#tree{data = D}) -> D;
data(T) -> erlang:error({badarg, T}).


%% =====================================================================
%% Primitives for backwards compatibility; for internal use only
%% =====================================================================


%% =====================================================================
%% @doc Creates a wrapper structure around an `erl_parse'
%% "parse tree".
%%
%% This function and the related {@link unwrap/1} and
%% {@link is_wrapper/1} provide a uniform way to attach arbitrary
%% information to an `erl_parse' tree. Some information about
%% the encapsuled tree may be cached in the wrapper, such as the node
%% type. All functions on syntax trees must behave so that the user sees
%% no difference between wrapped and non-wrapped `erl_parse'
%% trees. <em>Attaching a wrapper onto another wrapper structure is an
%% error</em>.

-doc """
Creates a wrapper structure around an `erl_parse` "parse tree".

This function and the related `unwrap/1` and `is_wrapper/1` provide a uniform
way to attach arbitrary information to an `erl_parse` tree. Some information
about the encapsuled tree may be cached in the wrapper, such as the node type.
All functions on syntax trees must behave so that the user sees no difference
between wrapped and non-wrapped `erl_parse` trees. _Attaching a wrapper onto
another wrapper structure is an error_.
""".
-spec wrap(erl_parse()) -> wrapper().

wrap(Node) ->
    %% We assume that Node is an old-school `erl_parse' tree.
    #wrapper{type = type(Node), attr = #attr{pos = get_pos(Node)},
	     tree = Node}.


%% =====================================================================
%% @doc Removes any wrapper structure, if present. If `Node'
%% is a wrapper structure, this function returns the wrapped
%% `erl_parse' tree; otherwise it returns `Node'
%% itself.

-doc """
Removes any wrapper structure, if present. If `Node` is a wrapper structure,
this function returns the wrapped `erl_parse` tree; otherwise it returns `Node`
itself.
""".
-spec unwrap(syntaxTree()) -> tree() | erl_parse().

unwrap(#wrapper{tree = Node}) -> Node;
unwrap(Node) -> Node.	 % This could also be a new-form node.


%% =====================================================================
%% @doc Returns `true' if the argument is a wrapper
%% structure, otherwise `false'.

-ifndef(NO_UNUSED).
-spec is_wrapper(term()) -> boolean().

is_wrapper(#wrapper{}) ->
    true;
is_wrapper(_) ->
    false.
-endif.


%% =====================================================================
%% General utility functions for internal use
%% =====================================================================

-doc """
is_printable(S)

Returns `true` if the argument is a wrapper structure, otherwise `false`.
""".
is_printable(S) ->
    io_lib:printable_list(S).

%% Support functions for transforming lists of function names
%% specified as `arity_qualifier' nodes.

unfold_function_names(Ns, Pos) ->
    F = fun ({Atom, Arity}) ->
		N = arity_qualifier(atom(Atom), integer(Arity)),
		set_pos(N, Pos)
	end,
    [F(N) || N <- Ns].

fold_function_names(Ns) ->
    [fold_function_name(N) || N <- Ns].

fold_function_name(N) ->
    Name = arity_qualifier_body(N),
    Arity = arity_qualifier_argument(N),
    true = ((type(Name) =:= atom) and (type(Arity) =:= integer)),
    {concrete(Name), concrete(Arity)}.

fold_variable_names(Vs) ->
    [variable_name(V) || V <- Vs].

unfold_variable_names(Vs, Pos) ->
    [set_pos(variable(V), Pos) || V <- Vs].


%% Support functions for transforming lists of record field definitions.
%%
%% There is no unique representation for field definitions in the
%% standard form. There, they may only occur in the "fields" part of a
%% record expression or declaration, and are represented as
%% `{record_field, Pos, Name, Value}', or as `{record_field, Pos, Name}'
%% if the value part is left out. However, these cannot be distinguished
%% out of context from the representation of record field access
%% expressions (see `record_access').

fold_record_fields(Fs) ->
    [fold_record_field(F) || F <- Fs].

fold_record_field(F) ->
    case type(F) of
        typed_record_field ->
            Field = fold_record_field_1(typed_record_field_body(F)),
            Type = typed_record_field_type(F),
            {typed_record_field, Field, Type};
        record_field ->
            fold_record_field_1(F)
    end.

fold_record_field_1(F) ->
    Pos = get_pos(F),
    Name = record_field_name(F),
    case record_field_value(F) of
	none ->
	    {record_field, Pos, Name};
	Value ->
	    {record_field, Pos, Name, Value}
    end.

unfold_record_fields(Fs) ->
    [unfold_record_field(F) || F <- Fs].

unfold_record_field({typed_record_field, Field, Type}) ->
    F = unfold_record_field_1(Field),
    set_pos(typed_record_field(F, Type), get_pos(F));
unfold_record_field(Field) ->
    unfold_record_field_1(Field).

unfold_record_field_1({record_field, Pos, Name}) ->
    set_pos(record_field(Name), Pos);
unfold_record_field_1({record_field, Pos, Name, Value}) ->
    set_pos(record_field(Name, Value), Pos).

fold_binary_field_types(Ts) ->
    [fold_binary_field_type(T) || T <- Ts].

fold_binary_field_type(Node) ->
    case type(Node) of
	size_qualifier ->
	    {concrete(size_qualifier_body(Node)),
	     concrete(size_qualifier_argument(Node))};
	_ ->
	    concrete(Node)
    end.

unfold_binary_field_types(Ts, Pos) ->
    [unfold_binary_field_type(T, Pos) || T <- Ts].

unfold_binary_field_type({Type, Size}, Pos) ->
    set_pos(size_qualifier(atom(Type), integer(Size)), Pos);
unfold_binary_field_type(Type, Pos) ->
    set_pos(atom(Type), Pos).

%% =====================================================================
