Text.ParserCombinators.Poly.Lazy

polyparse-1.12: A variety of alternative parser combinator libraries.

Safe Haskell | None
Language | Haskell98

Text.ParserCombinators.Poly.Lazy

Contents

- The Parser datatype
  - Basic parsers
  - Re-parsing
- Re-export all more general combinators

Synopsis

- newtype Parser t a = P (Parser t a)
- data Result z a
  - = Success z a
  - | Failure z String
  - | Committed (Result z a)
- runParser :: Parser t a -> [t] -> (a, [t])
- next :: Parser t t
- eof :: Parser t ()
- satisfy :: (t -> Bool) -> Parser t t
- satisfyMsg :: Show t => (t -> Bool) -> String -> Parser t t
- onFail :: Parser t a -> Parser t a -> Parser t a
- reparse :: [t] -> Parser t ()
- module Text.ParserCombinators.Poly.Base
- module Control.Applicative

# The Parser datatype

newtype Parser t a #

The only differences between a Plain and a Lazy parser are the instance of Applicative, and the type (and implementation) of runParser. We therefore need to newtype the original Parser type, to allow it to have a different instance.

Constructors

P (Parser t a) |

Instances

Monad (Parser t) # |
Methods (>>=) :: Parser t a -> (a -> Parser t b) -> Parser t b # (>>) :: Parser t a -> Parser t b -> Parser t b # return :: a -> Parser t a # fail :: String -> Parser t a #
Functor (Parser t) # |
Methods fmap :: (a -> b) -> Parser t a -> Parser t b # (<$) :: a -> Parser t b -> Parser t a #
Applicative (Parser t) # |
Methods pure :: a -> Parser t a # (<*>) :: Parser t (a -> b) -> Parser t a -> Parser t b # (*>) :: Parser t a -> Parser t b -> Parser t b # (<*) :: Parser t a -> Parser t b -> Parser t a #
Alternative (Parser t) # |
Methods empty :: Parser t a # (<|>) :: Parser t a -> Parser t a -> Parser t a # some :: Parser t a -> Parser t [a] # many :: Parser t a -> Parser t [a] #
PolyParse (Parser t) # |
Commitment (Parser t) # |
Methods commit :: Parser t a -> Parser t a # adjustErr :: Parser t a -> (String -> String) -> Parser t a # oneOf' :: [(String, Parser t a)] -> Parser t a #

data Result z a #

A return type like Either, that distinguishes not only between right and wrong answers, but also has commitment, so that a failure cannot be undone. This should only be used for writing very primitive parsers - really it is an internal detail of the library. The z type is the remaining unconsumed input.

Constructors

Success z a |
Failure z String |
Committed (Result z a) |

Instances

Functor (Result z) # |
Methods fmap :: (a -> b) -> Result z a -> Result z b # (<$) :: a -> Result z b -> Result z a #

runParser :: Parser t a -> [t] -> (a, [t]) #

Apply a parser to an input token sequence.

## Basic parsers

next :: Parser t t #

Simply return the next token in the input tokenstream.

eof :: Parser t () #

Succeed if the end of file/input has been reached, fail otherwise.

satisfy :: (t -> Bool) -> Parser t t #

Return the next token if it satisfies the given predicate.

satisfyMsg :: Show t => (t -> Bool) -> String -> Parser t t #

Return the next token if it satisfies the given predicate. The String argument describes the predicate for better error messages.

onFail :: Parser t a -> Parser t a -> Parser t a #

`p `onFail` q` means parse p, unless p fails, in which case parse q instead. Can be chained together to give multiple attempts to parse something. (Note that q could itself be a failing parser, e.g. to change the error message from that defined in p to something different.) However, a severe failure in p cannot be ignored.

## Re-parsing

reparse :: [t] -> Parser t () #

Push some tokens back onto the front of the input stream and reparse. This is useful e.g. for recursively expanding macros. When the user-parser recognises a macro use, it can lookup the macro expansion from the parse state, lex it, and then stuff the lexed expansion back down into the parser.

# Re-export all more general combinators

module Text.ParserCombinators.Poly.Base

module Control.Applicative