Text.ParserCombinators.Poly.Text

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

Safe Haskell | Safe
Language | Haskell98

Text.ParserCombinators.Poly.Text

Contents

- The Parser datatype
  - Basic parsers
  - Derived parsers (but implemented more efficiently)
  - Re-parsing
- Re-export all more general combinators

Synopsis

- newtype Parser a = P (Text -> Result Text a)
- data Result z a
  - = Success z a
  - | Failure z String
  - | Committed (Result z a)
- runParser :: Parser a -> Text -> (Either String a, Text)
- next :: Parser Char
- eof :: Parser ()
- satisfy :: (Char -> Bool) -> Parser Char
- onFail :: Parser a -> Parser a -> Parser a
- manySatisfy :: (Char -> Bool) -> Parser Text
- many1Satisfy :: (Char -> Bool) -> Parser Text
- reparse :: Text -> Parser ()
- module Text.ParserCombinators.Poly.Base
- module Control.Applicative

# The Parser datatype

newtype Parser a

This `Parser` datatype is a specialised parsing monad with error reporting. Whereas the standard version can be used for arbitrary token types, this version is specialised to Text input only.

Constructors

P (Text -> Result Text a) |

Instances

Monad Parser |
Functor Parser |
Applicative Parser |
Alternative Parser |
PolyParse Parser |
Commitment Parser |

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) |

runParser :: Parser a -> Text -> (Either String a, Text)

Apply a parser to an input token sequence.

## Basic parsers

next :: Parser Char

Simply return the next token in the input tokenstream.

eof :: Parser ()

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

satisfy :: (Char -> Bool) -> Parser Char

Return the next token if it satisfies the given predicate.

onFail :: Parser a -> Parser a -> Parser 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.

## Derived parsers (but implemented more efficiently)

manySatisfy :: (Char -> Bool) -> Parser Text

`manySatisfy p` is a more efficient fused version of `many (satisfy p)`

many1Satisfy :: (Char -> Bool) -> Parser Text

`many1Satisfy p` is a more efficient fused version of `many1 (satisfy p)`

## Re-parsing

reparse :: Text -> Parser ()

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