Text.PrettyPrint.Annotated.Leijen

annotated-wl-pprint-0.7.0: The Wadler/Leijen Pretty Printer, with annotation support

Safe Haskell | Safe
Language | Haskell98

Text.PrettyPrint.Annotated.Leijen

Contents

- Documents, parametrized by their annotations
- Basic combinators
- Alignment
- Operators
- List combinators
- Fillers
- Bracketing combinators
- Character documents
- Primitive type documents
- Pretty class
- Semantic annotations
- Rendering
- Undocumented

Synopsis

- data Doc a
- putDoc :: Doc a -> IO ()
- hPutDoc :: Handle -> Doc a -> IO ()
- empty :: Doc a
- char :: Char -> Doc a
- text :: String -> Doc a
- (<>) :: Doc a -> Doc a -> Doc a
- nest :: Int -> Doc a -> Doc a
- line :: Doc a
- linebreak :: Doc a
- group :: Doc a -> Doc a
- softline :: Doc a
- softbreak :: Doc a
- align :: Doc a -> Doc a
- hang :: Int -> Doc a -> Doc a
- indent :: Int -> Doc a -> Doc a
- encloseSep :: Doc a -> Doc a -> Doc a -> [Doc a] -> Doc a
- list :: [Doc a] -> Doc a
- tupled :: [Doc a] -> Doc a
- semiBraces :: [Doc a] -> Doc a
- (<+>) :: Doc a -> Doc a -> Doc a
- (<$>) :: Doc a -> Doc a -> Doc a
- (</>) :: Doc a -> Doc a -> Doc a
- (<$$>) :: Doc a -> Doc a -> Doc a
- (<//>) :: Doc a -> Doc a -> Doc a
- hsep :: [Doc a] -> Doc a
- vsep :: [Doc a] -> Doc a
- fillSep :: [Doc a] -> Doc a
- sep :: [Doc a] -> Doc a
- hcat :: [Doc a] -> Doc a
- vcat :: [Doc a] -> Doc a
- fillCat :: [Doc a] -> Doc a
- cat :: [Doc a] -> Doc a
- punctuate :: Doc a -> [Doc a] -> [Doc a]
- fill :: Int -> Doc a -> Doc a
- fillBreak :: Int -> Doc a -> Doc a
- enclose :: Doc a -> Doc a -> Doc a -> Doc a
- squotes :: Doc a -> Doc a
- dquotes :: Doc a -> Doc a
- parens :: Doc a -> Doc a
- angles :: Doc a -> Doc a
- braces :: Doc a -> Doc a
- brackets :: Doc a -> Doc a
- lparen :: Doc a
- rparen :: Doc a
- langle :: Doc a
- rangle :: Doc a
- lbrace :: Doc a
- rbrace :: Doc a
- lbracket :: Doc a
- rbracket :: Doc a
- squote :: Doc a
- dquote :: Doc a
- semi :: Doc a
- colon :: Doc a
- comma :: Doc a
- space :: Doc a
- dot :: Doc a
- backslash :: Doc a
- equals :: Doc a
- pipe :: Doc a
- string :: String -> Doc a
- int :: Int -> Doc a
- integer :: Integer -> Doc a
- float :: Float -> Doc a
- double :: Double -> Doc a
- rational :: Rational -> Doc a
- bool :: Bool -> Doc a
- annotate :: a -> Doc a -> Doc a
- noAnnotate :: Doc a -> Doc a
- data SimpleDoc a
  - = SEmpty
  - | SChar Char (SimpleDoc a)
  - | SText !Int String (SimpleDoc a)
  - | SLine !Int (SimpleDoc a)
  - | SAnnotStart a (SimpleDoc a)
  - | SAnnotStop (SimpleDoc a)
- renderPretty :: Float -> Int -> Doc a -> SimpleDoc a
- renderCompact :: Doc a -> SimpleDoc a
- displayDecorated :: (a -> String -> String) -> SimpleDoc a -> String
- displayDecoratedA :: (Applicative f, Monoid b) => (String -> f b) -> (a -> f b) -> (a -> f b) -> SimpleDoc a -> f b
- display :: SimpleDoc a -> String
- displayS :: SimpleDoc a -> ShowS
- displayIO :: Handle -> SimpleDoc a -> IO ()
- type SpanList a = [(Int, Int, a)]
- displaySpans :: SimpleDoc a -> (String, SpanList a)
- column :: (Int -> Doc a) -> Doc a
- nesting :: (Int -> Doc a) -> Doc a
- width :: Doc a -> (Int -> Doc a) -> Doc a

# Documents, parametrized by their annotations

data Doc a

The abstract data type `Doc a` represents pretty documents.

`Doc a` is an instance of the `Show` class. `(show doc)` pretty prints document `doc` with a page width of 100 characters and a ribbon width of 40 characters.

    show (text "hello" <$> text "world")

Which would return the string "hello\nworld", i.e.

    hello
    world

Instances

Functor Doc |
Show (Doc a) |
IsString (Doc a) |

putDoc :: Doc a -> IO ()

The action `(putDoc doc)` pretty prints document `doc` to the standard output, with a page width of 100 characters and a ribbon width of 40 characters.

    main :: IO ()
    main = do{ putDoc (text "hello" <+> text "world") }

Which would output

    hello world

hPutDoc :: Handle -> Doc a -> IO ()

`(hPutDoc handle doc)` pretty prints document `doc` to the file handle `handle` with a page width of 100 characters and a ribbon width of 40 characters.

    main = do{ handle <- openFile "MyFile" WriteMode
             ; hPutDoc handle (vcat (map text
                               ["vertical","text"]))
             ; hClose handle
             }

# Basic combinators

empty :: Doc a

The empty document is, indeed, empty. Although `empty` has no content, it does have a 'height' of 1 and behaves exactly like `(text "")` (and is therefore not a unit of `<$>`).

char :: Char -> Doc a

The document `(char c)` contains the literal character `c`. The character shouldn't be a newline (`'\n'`), the function `line` should be used for line breaks.

text :: String -> Doc a

The document `(text s)` contains the literal string `s`. The string shouldn't contain any newline (`'\n'`) characters. If the string contains newline characters, the function `string` should be used.

(<>) :: Doc a -> Doc a -> Doc a infixr 6

The document `(x <> y)` concatenates document `x` and document `y`. It is an associative operation having `empty` as a left and right unit. (infixr 6)

nest :: Int -> Doc a -> Doc a

The document `(nest i x)` renders document `x` with the current indentation level increased by i (See also `hang`, `align` and `indent`).

    nest 2 (text "hello" <$> text "world") <$> text "!"

outputs as:

    hello
      world
    !

line :: Doc a

The `line` document advances to the next line and indents to the current nesting level. Doc aument `line` behaves like `(text " ")` if the line break is undone by `group`.

linebreak :: Doc a

The `linebreak` document advances to the next line and indents to the current nesting level. Document `linebreak` behaves like `empty` if the line break is undone by `group`.

group :: Doc a -> Doc a

The `group` combinator is used to specify alternative layouts. The document `(group x)` undoes all line breaks in document `x`. The resulting line is added to the current line if that fits the page. Otherwise, the document `x` is rendered without any changes.

softline :: Doc a

The document `softline` behaves like `space` if the resulting output fits the page, otherwise it behaves like `line`.

    softline = group line

softbreak :: Doc a

The document `softbreak` behaves like `empty` if the resulting output fits the page, otherwise it behaves like `line`.

    softbreak  = group linebreak

# Alignment

align :: Doc a -> Doc a

The document `(align x)` renders document `x` with the nesting level set to the current column. It is used for example to implement `hang`.

As an example, we will put a document right above another one, regardless of the current nesting level:

    x $$ y  = align (x <$> y)

    test    = text "hi" <+> (text "nice" $$ text "world")

which will be layed out as:

    hi nice
       world

hang :: Int -> Doc a -> Doc a

The hang combinator implements hanging indentation. The document `(hang i x)` renders document `x` with a nesting level set to the current column plus `i`. The following example uses hanging indentation for some text:

    test  = hang 4 (fillSep (map text
            (words "the hang combinator indents these words !")))

Which lays out on a page with a width of 20 characters as:

    the hang combinator
        indents these
        words !

The `hang` combinator is implemented as:

    hang i x  = align (nest i x)

indent :: Int -> Doc a -> Doc a

The document `(indent i x)` indents document `x` with `i` spaces.

    test  = indent 4 (fillSep (map text
            (words "the indent combinator indents these words !")))

Which lays out with a page width of 20 as:

        the indent
        combinator
        indents these
        words !

encloseSep :: Doc a -> Doc a -> Doc a -> [Doc a] -> Doc a

The document `(encloseSep l r sep xs)` concatenates the documents `xs` separated by `sep` and encloses the resulting document by `l` and `r`. The documents are rendered horizontally if that fits the page. Otherwise they are aligned vertically. All separators are put in front of the elements. For example, the combinator `list` can be defined with `encloseSep`:

    list xs = encloseSep lbracket rbracket comma xs
    test    = text "list" <+> (list (map int [10,200,3000]))

Which is layed out with a page width of 20 as:

    list [10,200,3000]

But when the page width is 15, it is layed out as:

    list [10
         ,200
         ,3000]

list :: [Doc a] -> Doc a

The document `(list xs)` comma separates the documents `xs` and encloses them in square brackets. The documents are rendered horizontally if that fits the page. Otherwise they are aligned vertically. All comma separators are put in front of the elements.

tupled :: [Doc a] -> Doc a

The document `(tupled xs)` comma separates the documents `xs` and encloses them in parenthesis. The documents are rendered horizontally if that fits the page. Otherwise they are aligned vertically. All comma separators are put in front of the elements.

semiBraces :: [Doc a] -> Doc a

The document `(semiBraces xs)` separates the documents `xs` with semi colons and encloses them in braces. The documents are rendered horizontally if that fits the page. Otherwise they are aligned vertically. All semi colons are put in front of the elements.

# Operators

(<+>) :: Doc a -> Doc a -> Doc a infixr 6

The document `(x <+> y)` concatenates document `x` and `y` with a `space` in between. (infixr 6)

(<$>) :: Doc a -> Doc a -> Doc a infixr 5

The document `(x <$> y)` concatenates document `x` and `y` with a `line` in between. (infixr 5)

(</>) :: Doc a -> Doc a -> Doc a infixr 5

The document `(x </> y)` concatenates document `x` and `y` with a `softline` in between. This effectively puts `x` and `y` either next to each other (with a `space` in between) or underneath each other. (infixr 5)

(<$$>) :: Doc a -> Doc a -> Doc a infixr 5

The document `(x <$$> y)` concatenates document `x` and `y` with a `linebreak` in between. (infixr 5)

(<//>) :: Doc a -> Doc a -> Doc a infixr 5

The document `(x <//> y)` concatenates document `x` and `y` with a `softbreak` in between. This effectively puts `x` and `y` either right next to each other or underneath each other. (infixr 5)

# List combinators

hsep :: [Doc a] -> Doc a

The document `(hsep xs)` concatenates all documents `xs` horizontally with (`<+>`).

vsep :: [Doc a] -> Doc a

The document `(vsep xs)` concatenates all documents `xs` vertically with `(<$>)`. If a `group` undoes the line breaks inserted by `vsep`, all documents are separated with a space.

    someText = map text (words ("text to lay out"))

    test     = text "some" <+> vsep someText

This is layed out as:

    some text
    to
    lay
    out

The `align` combinator can be used to align the documents under their first element

    test     = text "some" <+> align (vsep someText)

Which is printed as:

    some text
         to
         lay
         out

fillSep :: [Doc a] -> Doc a

The document `(fillSep xs)` concatenates documents `xs` horizontally with `(<+>)` as long as its fits the page, than inserts a `line` and continues doing that for all documents in `xs`.

    fillSep xs  = foldr (</>) empty xs

sep :: [Doc a] -> Doc a

The document `(sep xs)` concatenates all documents `xs` either horizontally with `(<+>)`, if it fits the page, or vertically with `(<$>)`.

    sep xs  = group (vsep xs)

hcat :: [Doc a] -> Doc a

The document `(hcat xs)` concatenates all documents `xs` horizontally with `(<>)`.

vcat :: [Doc a] -> Doc a

The document `(vcat xs)` concatenates all documents `xs` vertically with `(<$$>)`. If a `group` undoes the line breaks inserted by `vcat`, all documents are directly concatenated.

fillCat :: [Doc a] -> Doc a

The document `(fillCat xs)` concatenates documents `xs` horizontally with `(<>)` as long as its fits the page, than inserts a `linebreak` and continues doing that for all documents in `xs`.

    fillCat xs  = foldr (\<\/\/\>) empty xs

cat :: [Doc a] -> Doc a

The document `(cat xs)` concatenates all documents `xs` either horizontally with `(<>)`, if it fits the page, or vertically with `(<$$>)`.

    cat xs  = group (vcat xs)

punctuate :: Doc a -> [Doc a] -> [Doc a]

`(punctuate p xs)` concatenates all documents in `xs` with document `p` except for the last document.

    someText = map text ["words","in","a","tuple"]
    test     = parens (align (cat (punctuate comma someText)))

This is layed out on a page width of 20 as:

    (words,in,a,tuple)

But when the page width is 15, it is layed out as:

    (words,
     in,
     a,
     tuple)

(If you want put the commas in front of their elements instead of at the end, you should use `tupled` or, in general, `encloseSep`.)

# Fillers

fill :: Int -> Doc a -> Doc a

The document `(fill i x)` renders document `x`. It than appends `space`s until the width is equal to `i`. If the width of `x` is already larger, nothing is appended. This combinator is quite useful in practice to output a list of bindings. The following example demonstrates this.

    types  = [("empty","Doc a")
             ,("nest","Int -> Doc a -> Doc a")
             ,("linebreak","Doc a")]

    ptype (name,tp)
           = fill 6 (text name) <+> text "::" <+> text tp

    test   = text "let" <+> align (vcat (map ptype types))

Which is layed out as:

    let empty  :: Doc a
        nest   :: Int -> Doc a -> Doc a
        linebreak :: Doc a

fillBreak :: Int -> Doc a -> Doc a

The document `(fillBreak i x)` first renders document `x`. It than appends `space`s until the width is equal to `i`. If the width of `x` is already larger than `i`, the nesting level is increased by `i` and a `line` is appended. When we redefine `ptype` in the previous example to use `fillBreak`, we get a useful variation of the previous output:

    ptype (name,tp)
           = fillBreak 6 (text name) <+> text "::" <+> text tp

The output will now be:

    let empty  :: Doc a
        nest   :: Int -> Doc a -> Doc a
        linebreak
               :: Doc a

# Bracketing combinators

enclose :: Doc a -> Doc a -> Doc a -> Doc a

The document `(enclose l r x)` encloses document `x` between documents `l` and `r` using `(<>)`.

    enclose l r x   = l <> x <> r

squotes :: Doc a -> Doc a

Document `(squotes x)` encloses document `x` with single quotes "'".

dquotes :: Doc a -> Doc a

Document `(dquotes x)` encloses document `x` with double quotes '"'.

parens :: Doc a -> Doc a

Document `(parens x)` encloses document `x` in parenthesis, "(" and ")".

angles :: Doc a -> Doc a

Document `(angles x)` encloses document `x` in angles, "<" and ">".

braces :: Doc a -> Doc a

Document `(braces x)` encloses document `x` in braces, "{" and "}".

brackets :: Doc a -> Doc a

Document `(brackets x)` encloses document `x` in square brackets, "[" and "]".

# Character documents

lparen :: Doc a

The document `lparen` contains a left parenthesis, "(".

rparen :: Doc a

The document `rparen` contains a right parenthesis, ")".

langle :: Doc a

The document `langle` contains a left angle, "<".

rangle :: Doc a

The document `rangle` contains a right angle, ">".

lbrace :: Doc a

The document `lbrace` contains a left brace, "{".

rbrace :: Doc a

The document `rbrace` contains a right brace, "}".

lbracket :: Doc a

The document `lbracket` contains a left square bracket, "[".

rbracket :: Doc a

The document `rbracket` contains a right square bracket, "]".

squote :: Doc a

The document `squote` contains a single quote, "'".

dquote :: Doc a

The document `dquote` contains a double quote, '"'.

semi :: Doc a

The document `semi` contains a semi colon, ";".

colon :: Doc a

The document `colon` contains a colon, ":".

comma :: Doc a

The document `comma` contains a comma, ",".

space :: Doc a

The document `space` contains a single space, " ".

    x <+> y   = x <> space <> y

dot :: Doc a

The document `dot` contains a single dot, ".".

backslash :: Doc a

The document `backslash` contains a back slash, "\".

equals :: Doc a

The document `equals` contains an equal sign, "=".

pipe :: Doc a

The document `pipe` contains a pipe character, "|".

# Primitive type documents

string :: String -> Doc a

The document `(string s)` concatenates all characters in `s` using `line` for newline characters and `char` for all other characters. It is used instead of `text` whenever the text contains newline characters.

int :: Int -> Doc a

The document `(int i)` shows the literal integer `i` using `text`.

integer :: Integer -> Doc a

The document `(integer i)` shows the literal integer `i` using `text`.

float :: Float -> Doc a

The document `(float f)` shows the literal float `f` using `text`.

double :: Double -> Doc a

The document `(double d)` shows the literal double `d` using `text`.

rational :: Rational -> Doc a

The document `(rational r)` shows the literal rational `r` using `text`.

bool :: Bool -> Doc a

The document `(bool b)` is `text True` when `b` is true, and `text False` otherwise.

# Pretty class

# Semantic annotations

annotate :: a -> Doc a -> Doc a

noAnnotate :: Doc a -> Doc a

Strip annotations from a document. This is useful for re-using the textual formatting of some sub-document, but applying a different high-level annotation.

# Rendering

data SimpleDoc a

The data type `SimpleDoc a` represents rendered documents and is used by the display functions.

The `Int` in `SText` contains the length of the string. The `Int` in `SLine` contains the indentation for that line. The library provides two default display functions `displayS` and `displayIO`. You can provide your own display function by writing a function from a `SimpleDoc a` to your own output format.

Constructors

SEmpty |
SChar Char (SimpleDoc a) |
SText !Int String (SimpleDoc a) |
SLine !Int (SimpleDoc a) |
SAnnotStart a (SimpleDoc a) |
SAnnotStop (SimpleDoc a) |

Instances

Functor SimpleDoc |

renderPretty :: Float -> Int -> Doc a -> SimpleDoc a

This is the default pretty printer which is used by `show`, `putDoc` and `hPutDoc`. `(renderPretty ribbonfrac width x)` renders document `x` with a page width of `width` and a ribbon width of `(ribbonfrac * width)` characters. The ribbon width is the maximal amount of non-indentation characters on a line. The parameter `ribbonfrac` should be between `0.0` and `1.0`. If it is lower or higher, the ribbon width will be 0 or `width` respectively.

renderCompact :: Doc a -> SimpleDoc a

`(renderCompact x)` renders document `x` without adding any indentation. Since no 'pretty' printing is involved, this renderer is very fast. The resulting output contains fewer characters than a pretty printed version and can be used for output that is read by other programs.

displayDecorated :: (a -> String -> String) -> SimpleDoc a -> String

Render a string, where annotated regions are decorated by a user-provided function.

displayDecoratedA :: (Applicative f, Monoid b) => (String -> f b) -> (a -> f b) -> (a -> f b) -> SimpleDoc a -> f b

display :: SimpleDoc a -> String

`(display simpleDoc)` transforms the `simpleDoc` to a `String`.

displayS :: SimpleDoc a -> ShowS

`(displayS simpleDoc a)` takes the output `simpleDoc a` from a rendering function and transforms it to a `ShowS` type (for use in the `Show` class).

    showWidth :: Int -> Doc a -> String
    showWidth w x   = displayS (renderPretty 0.4 w x) ""

displayIO :: Handle -> SimpleDoc a -> IO ()

`(displayIO handle simpleDoc a)` writes `simpleDoc a` to the file handle `handle`. This function is used for example by 'hPutDoc a':

    hPutDoc a handle doc  = displayIO handle (renderPretty 0.4 100 doc)

type SpanList a = [(Int, Int, a)]

displaySpans :: SimpleDoc a -> (String, SpanList a)

Generate a pair of a string and a list of source span/annotation pairs

# Undocumented

column :: (Int -> Doc a) -> Doc a

nesting :: (Int -> Doc a) -> Doc a

width :: Doc a -> (Int -> Doc a) -> Doc a