attoparsec-0.13.0.1: Fast combinator parsing for bytestrings and text

Copyright | Daan Leijen 1999-2001, Bryan O'Sullivan 2007-2015
License | BSD3
Maintainer | bos@serpentine.com
Stability | experimental
Portability | portable
Safe Haskell | Trustworthy
Language | Haskell98

Data.Attoparsec.Combinator

Contents

- Combinators

Description

Useful parser combinators, similar to those provided by Parsec.

Synopsis

- try :: Parser i a -> Parser i a
- (<?>) :: Parser i a -> String -> Parser i a
- choice :: Alternative f => [f a] -> f a
- count :: Monad m => Int -> m a -> m [a]
- option :: Alternative f => a -> f a -> f a
- many' :: MonadPlus m => m a -> m [a]
- many1 :: Alternative f => f a -> f [a]
- many1' :: MonadPlus m => m a -> m [a]
- manyTill :: Alternative f => f a -> f b -> f [a]
- manyTill' :: MonadPlus m => m a -> m b -> m [a]
- sepBy :: Alternative f => f a -> f s -> f [a]
- sepBy' :: MonadPlus m => m a -> m s -> m [a]
- sepBy1 :: Alternative f => f a -> f s -> f [a]
- sepBy1' :: MonadPlus m => m a -> m s -> m [a]
- skipMany :: Alternative f => f a -> f ()
- skipMany1 :: Alternative f => f a -> f ()
- eitherP :: Alternative f => f a -> f b -> f (Either a b)
- feed :: Monoid i => IResult i r -> i -> IResult i r
- satisfyElem :: forall t. Chunk t => (ChunkElem t -> Bool) -> Parser t (ChunkElem t)
- endOfInput :: forall t. Chunk t => Parser t ()
- atEnd :: Chunk t => Parser t Bool
- lookAhead :: Parser i a -> Parser i a

# Combinators

try :: Parser i a -> Parser i a

Attempt a parse, and if it fails, rewind the input so that no input appears to have been consumed.

This combinator is provided for compatibility with Parsec. attoparsec parsers always backtrack on failure.

(<?>) infix 0

Arguments

:: Parser i a |
-> String | the name to use if parsing fails
-> Parser i a |

Name the parser, in case failure occurs.

choice :: Alternative f => [f a] -> f a

`choice ps` tries to apply the actions in the list `ps` in order, until one of them succeeds. Returns the value of the succeeding action.

count :: Monad m => Int -> m a -> m [a]

Apply the given action repeatedly, returning every result.

option :: Alternative f => a -> f a -> f a

`option x p` tries to apply action `p`. If `p` fails without consuming input, it returns the value `x`, otherwise the value returned by `p`.

    priority  = option 0 (digitToInt <$> digit)

many' :: MonadPlus m => m a -> m [a]

`many' p` applies the action `p` zero or more times. Returns a list of the returned values of `p`. The value returned by `p` is forced to WHNF.

     word  = many' letter

many1 :: Alternative f => f a -> f [a]

`many1 p` applies the action `p` one or more times. Returns a list of the returned values of `p`.

     word  = many1 letter

many1' :: MonadPlus m => m a -> m [a]

`many1' p` applies the action `p` one or more times. Returns a list of the returned values of `p`. The value returned by `p` is forced to WHNF.

     word  = many1' letter

manyTill :: Alternative f => f a -> f b -> f [a]

`manyTill p end` applies action `p` zero or more times until action `end` succeeds, and returns the list of values returned by `p`. This can be used to scan comments:

     simpleComment   = string "<!--" *> manyTill anyChar (string "-->")

(Note the overlapping parsers `anyChar` and `string "-->"`. While this will work, it is not very efficient, as it will cause a lot of backtracking.)

manyTill' :: MonadPlus m => m a -> m b -> m [a]

`manyTill' p end` applies action `p` zero or more times until action `end` succeeds, and returns the list of values returned by `p`. This can be used to scan comments:

     simpleComment   = string "<!--" *> manyTill' anyChar (string "-->")

(Note the overlapping parsers `anyChar` and `string "-->"`. While this will work, it is not very efficient, as it will cause a lot of backtracking.)

The value returned by `p` is forced to WHNF.

sepBy :: Alternative f => f a -> f s -> f [a]

`sepBy p sep` applies zero or more occurrences of `p`, separated by `sep`. Returns a list of the values returned by `p`.

    commaSep p  = p `sepBy` (char ',')

sepBy' :: MonadPlus m => m a -> m s -> m [a]

`sepBy' p sep` applies zero or more occurrences of `p`, separated by `sep`. Returns a list of the values returned by `p`. The value returned by `p` is forced to WHNF.

    commaSep p  = p `sepBy'` (char ',')

sepBy1 :: Alternative f => f a -> f s -> f [a]

`sepBy1 p sep` applies one or more occurrences of `p`, separated by `sep`. Returns a list of the values returned by `p`.

    commaSep p  = p `sepBy1` (char ',')

sepBy1' :: MonadPlus m => m a -> m s -> m [a]

`sepBy1' p sep` applies one or more occurrences of `p`, separated by `sep`. Returns a list of the values returned by `p`. The value returned by `p` is forced to WHNF.

    commaSep p  = p `sepBy1'` (char ',')

skipMany :: Alternative f => f a -> f ()

Skip zero or more instances of an action.

skipMany1 :: Alternative f => f a -> f ()

Skip one or more instances of an action.

eitherP :: Alternative f => f a -> f b -> f (Either a b)

Combine two alternatives.

feed :: Monoid i => IResult i r -> i -> IResult i r

If a parser has returned a `Partial` result, supply it with more input.

satisfyElem :: forall t. Chunk t => (ChunkElem t -> Bool) -> Parser t (ChunkElem t)

The parser `satisfyElem p` succeeds for any chunk element for which the predicate `p` returns `True`. Returns the element that is actually parsed.

endOfInput :: forall t. Chunk t => Parser t ()

Match only if all input has been consumed.

atEnd :: Chunk t => Parser t Bool

Return an indication of whether the end of input has been reached.

lookAhead :: Parser i a -> Parser i a

Apply a parser without consuming any input.