Copyright | Bryan O'Sullivan 2007-2015 |
---|---|

License | BSD3 |

Maintainer | bos@serpentine.com |

Stability | experimental |

Portability | unknown |

Safe Haskell | Trustworthy |

Language | Haskell98 |

Simple, efficient combinator parsing that can consume lazy
`ByteString`

strings, loosely based on the Parsec library.

This is essentially the same code as in the `Attoparsec`

module, only with a `parse`

function that can consume a lazy
`ByteString`

incrementally, and a `Result`

type that does not allow
more input to be fed in. Think of this as suitable for use with a
lazily read file, e.g. via `readFile`

or `hGetContents`

.

*Note:* The various parser functions and combinators such as
`string`

still expect *strict* `ByteString`

parameters, and
return strict `ByteString`

results. Behind the scenes, strict
`ByteString`

values are still used internally to store parser
input and manipulate it efficiently.

## Synopsis

- data Result r
- = Fail ByteString [String] String
- | Done ByteString r

- compareResults :: (Eq i, Eq r) => IResult i r -> IResult i r -> Maybe Bool
- endOfInput :: forall t. Chunk t => Parser t ()
- atEnd :: Chunk t => Parser t Bool
- try :: Parser i a -> Parser i a
- (<?>) :: Parser i a -> String -> Parser i a
- choice :: Alternative f => [f a] -> f 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]
- 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]
- manyTill :: Alternative f => f a -> f b -> f [a]
- manyTill' :: MonadPlus m => m a -> m b -> m [a]
- skipMany :: Alternative f => f a -> f ()
- skipMany1 :: Alternative f => f a -> f ()
- count :: Monad m => Int -> m a -> m [a]
- eitherP :: Alternative f => f a -> f b -> f (Either a b)
- feed :: Monoid i => IResult i r -> i -> IResult i r
- type Parser = Parser ByteString
- satisfy :: (Word8 -> Bool) -> Parser Word8
- skip :: (Word8 -> Bool) -> Parser ()
- satisfyWith :: (Word8 -> a) -> (a -> Bool) -> Parser a
- take :: Int -> Parser ByteString
- string :: ByteString -> Parser ByteString
- skipWhile :: (Word8 -> Bool) -> Parser ()
- takeTill :: (Word8 -> Bool) -> Parser ByteString
- takeWhile :: (Word8 -> Bool) -> Parser ByteString
- takeByteString :: Parser ByteString
- takeLazyByteString :: Parser ByteString
- scan :: s -> (s -> Word8 -> Maybe s) -> Parser ByteString
- runScanner :: s -> (s -> Word8 -> Maybe s) -> Parser (ByteString, s)
- takeWhile1 :: (Word8 -> Bool) -> Parser ByteString
- inClass :: String -> Word8 -> Bool
- notInClass :: String -> Word8 -> Bool
- anyWord8 :: Parser Word8
- word8 :: Word8 -> Parser Word8
- notWord8 :: Word8 -> Parser Word8
- peekWord8 :: Parser (Maybe Word8)
- peekWord8' :: Parser Word8
- parseOnly :: Parser a -> ByteString -> Either String a
- match :: Parser a -> Parser (ByteString, a)
- parse :: Parser a -> ByteString -> Result a
- parseTest :: Show a => Parser a -> ByteString -> IO ()
- maybeResult :: Result r -> Maybe r
- eitherResult :: Result r -> Either String r

# Documentation

The result of a parse.

Fail ByteString [String] String | The parse failed. The |

Done ByteString r | The parse succeeded. The |

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.

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.

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.

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

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 ',')

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.

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.

type Parser = Parser ByteString #

satisfy :: (Word8 -> Bool) -> Parser Word8 #

The parser `satisfy p`

succeeds for any byte for which the
predicate `p`

returns `True`

. Returns the byte that is actually
parsed.

digit = satisfy isDigit where isDigit w = w >= 48 && w <= 57

skip :: (Word8 -> Bool) -> Parser () #

The parser `skip p`

succeeds for any byte for which the predicate
`p`

returns `True`

.

skipDigit = skip isDigit where isDigit w = w >= 48 && w <= 57

satisfyWith :: (Word8 -> a) -> (a -> Bool) -> Parser a #

The parser `satisfyWith f p`

transforms a byte, and succeeds if
the predicate `p`

returns `True`

on the transformed value. The
parser returns the transformed byte that was parsed.

take :: Int -> Parser ByteString #

Consume exactly `n`

bytes of input.

string :: ByteString -> Parser ByteString #

`string s`

parses a sequence of bytes that identically match
`s`

. Returns the parsed string (i.e. `s`

). This parser consumes no
input if it fails (even if a partial match).

*Note*: The behaviour of this parser is different to that of the
similarly-named parser in Parsec, as this one is all-or-nothing.
To illustrate the difference, the following parser will fail under
Parsec given an input of `"for"`

:

string "foo" <|> string "for"

The reason for its failure is that the first branch is a
partial match, and will consume the letters `'f'`

and `'o'`

before failing. In attoparsec, the above parser will *succeed* on
that input, because the failed first branch will consume nothing.

skipWhile :: (Word8 -> Bool) -> Parser () #

Skip past input for as long as the predicate returns `True`

.

takeTill :: (Word8 -> Bool) -> Parser ByteString #

Consume input as long as the predicate returns `False`

(i.e. until it returns `True`

), and return the consumed input.

This parser does not fail. It will return an empty string if the
predicate returns `True`

on the first byte of input.

*Note*: Because this parser does not fail, do not use it with
combinators such as `many`

, because such
parsers loop until a failure occurs. Careless use will thus result
in an infinite loop.

takeWhile :: (Word8 -> Bool) -> Parser ByteString #

Consume input as long as the predicate returns `True`

, and return
the consumed input.

This parser does not fail. It will return an empty string if the
predicate returns `False`

on the first byte of input.

*Note*: Because this parser does not fail, do not use it with
combinators such as `many`

, because such
parsers loop until a failure occurs. Careless use will thus result
in an infinite loop.

takeByteString :: Parser ByteString #

Consume all remaining input and return it as a single string.

takeLazyByteString :: Parser ByteString #

Consume all remaining input and return it as a single string.

scan :: s -> (s -> Word8 -> Maybe s) -> Parser ByteString #

A stateful scanner. The predicate consumes and transforms a
state argument, and each transformed state is passed to successive
invocations of the predicate on each byte of the input until one
returns `Nothing`

or the input ends.

This parser does not fail. It will return an empty string if the
predicate returns `Nothing`

on the first byte of input.

*Note*: Because this parser does not fail, do not use it with
combinators such as `many`

, because such
parsers loop until a failure occurs. Careless use will thus result
in an infinite loop.

runScanner :: s -> (s -> Word8 -> Maybe s) -> Parser (ByteString, s) #

Like `scan`

, but generalized to return the final state of the
scanner.

takeWhile1 :: (Word8 -> Bool) -> Parser ByteString #

inClass :: String -> Word8 -> Bool #

Match any byte in a set.

vowel = inClass "aeiou"

Range notation is supported.

halfAlphabet = inClass "a-nA-N"

To add a literal `'-'`

to a set, place it at the beginning or end
of the string.

notInClass :: String -> Word8 -> Bool #

Match any byte not in a set.

peekWord8 :: Parser (Maybe Word8) #

Match any byte, to perform lookahead. Returns `Nothing`

if end of
input has been reached. Does not consume any input.

*Note*: Because this parser does not fail, do not use it with
combinators such as `many`

, because such
parsers loop until a failure occurs. Careless use will thus result
in an infinite loop.

peekWord8' :: Parser Word8 #

Match any byte, to perform lookahead. Does not consume any input, but will fail if end of input has been reached.

parseOnly :: Parser a -> ByteString -> Either String a #

Run a parser that cannot be resupplied via a `Partial`

result.

This function does not force a parser to consume all of its input. Instead, any residual input will be discarded. To force a parser to consume all of its input, use something like this:

`parseOnly`

(myParser`<*`

`endOfInput`

)

match :: Parser a -> Parser (ByteString, a) #

Return both the result of a parse and the portion of the input that was consumed while it was being parsed.

# Running parsers

parse :: Parser a -> ByteString -> Result a #

Run a parser and return its result.

parseTest :: Show a => Parser a -> ByteString -> IO () #

Run a parser and print its result to standard output.