Data.Attoparsec.ByteString.Lazy

attoparsec-0.14.4: Fast combinator parsing for bytestrings and text

Copyright | Bryan O'Sullivan 2007-2015
License | BSD3
Maintainer | bos@serpentine.com
Stability | experimental
Portability | unknown
Safe Haskell | Trustworthy
Language | Haskell2010

Data.Attoparsec.ByteString.Lazy

Contents

- Running parsers
  - Result conversion

Description

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
- takeWhile :: (Word8 -> Bool) -> Parser ByteString
- take :: Int -> Parser ByteString
- satisfy :: (Word8 -> Bool) -> Parser Word8
- string :: ByteString -> Parser ByteString
- choice :: Alternative f => [f a] -> f a
- count :: Monad m => Int -> m a -> m [a]
- option :: Alternative f => a -> f a -> f a
- many1 :: Alternative f => f a -> f [a]
- skipMany :: Alternative f => f a -> f ()
- skipMany1 :: Alternative f => f a -> f ()
- sepBy :: Alternative f => f a -> f s -> f [a]
- sepBy1 :: Alternative f => f a -> f s -> f [a]
- manyTill :: Alternative f => f a -> f b -> f [a]
- try :: Parser i a -> Parser i a
- skip :: (Word8 -> Bool) -> Parser ()
- word8 :: Word8 -> Parser Word8
- match :: Parser a -> Parser (ByteString, a)
- type Parser = Parser ByteString
- compareResults :: (Eq i, Eq r) => IResult i r -> IResult i r -> Maybe Bool
- feed :: Monoid i => IResult i r -> i -> IResult i r
- anyWord8 :: Parser Word8
- notWord8 :: Word8 -> Parser Word8
- satisfyWith :: (Word8 -> a) -> (a -> Bool) -> Parser a
- peekWord8 :: Parser (Maybe Word8)
- peekWord8' :: Parser Word8
- inClass :: String -> Word8 -> Bool
- notInClass :: String -> Word8 -> Bool
- skipWhile :: (Word8 -> Bool) -> Parser ()
- scan :: s -> (s -> Word8 -> Maybe s) -> Parser ByteString
- runScanner :: s -> (s -> Word8 -> Maybe s) -> Parser (ByteString, s)
- takeWhile1 :: (Word8 -> Bool) -> Parser ByteString
- takeWhileIncluding :: (Word8 -> Bool) -> Parser ByteString
- takeTill :: (Word8 -> Bool) -> Parser ByteString
- getChunk :: Parser (Maybe ByteString)
- takeByteString :: Parser ByteString
- takeLazyByteString :: Parser ByteString
- (<?>) :: Parser i a -> String -> Parser i a
- many' :: MonadPlus m => m a -> m [a]
- many1' :: MonadPlus m => m a -> m [a]
- manyTill' :: MonadPlus m => m a -> m b -> m [a]
- sepBy' :: MonadPlus m => m a -> m s -> m [a]
- sepBy1' :: MonadPlus m => m a -> m s -> m [a]
- eitherP :: Alternative f => f a -> f b -> f (Either a b)
- endOfInput :: Chunk t => Parser t ()
- atEnd :: Chunk t => Parser t Bool
- parse :: Parser a -> ByteString -> Result a
- parseOnly :: Parser a -> ByteString -> Either String a
- parseTest :: Show a => Parser a -> ByteString -> IO ()
- maybeResult :: Result r -> Maybe r
- eitherResult :: Result r -> Either String r

# Documentation

data Result r #

The result of a parse.

Constructors

Fail ByteString [String] String | The parse failed. The `ByteString` is the input that had not yet been consumed when the failure occurred. The `[``String``]` is a list of contexts in which the error occurred. The `String` is the message describing the error, if any.
Done ByteString r | The parse succeeded. The `ByteString` is the input that had not yet been consumed (if any) when the parse succeeded.

#### Instances

Instances details

Functor Result # |
Instance details Defined in Data.Attoparsec.ByteString.Lazy Methods fmap :: (a -> b) -> Result a -> Result b # (<$) :: a -> Result b -> Result a #
NFData r => NFData (Result r) # |
Instance details Defined in Data.Attoparsec.ByteString.Lazy Methods rnf :: Result r -> () #
Show r => Show (Result r) # |
Instance details Defined in Data.Attoparsec.ByteString.Lazy Methods showsPrec :: Int -> Result r -> ShowS # show :: Result r -> String # showList :: [Result r] -> ShowS #

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.

take :: Int -> Parser ByteString #

Consume exactly `n` bytes of input.

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

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.

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)

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

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.

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 ',')

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 ',')

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.)

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.

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

word8 :: Word8 -> Parser Word8 #

Match a specific byte.

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.

type Parser = Parser ByteString #

compareResults :: (Eq i, Eq r) => IResult i r -> IResult i r -> Maybe Bool #

Compare two `IResult` values for equality.

If both `IResult`s are `Partial`, the result will be `Nothing`, as they are incomplete and hence their equality cannot be known. (This is why there is no `Eq` instance for `IResult`.)

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

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

anyWord8 :: Parser Word8 #

Match any byte.

notWord8 :: Word8 -> Parser Word8 #

Match any byte except the given one.

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.

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.

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.

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

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

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 #

Consume input as long as the predicate returns `True`, and return the consumed input.

This parser requires the predicate to succeed on at least one byte of input: it will fail if the predicate never returns `True` or if there is no input left.

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

Consume input until immediately after the predicate returns `True`, and return the consumed input.

This parser will consume at least one `Word8` or fail.

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.

getChunk :: Parser (Maybe ByteString) #

Return the rest of the current chunk without consuming anything.

If the current chunk is empty, then ask for more input. If there is no more input, then return `Nothing`

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.

(<?>) infix 0 #

Arguments

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

Name the parser, in case failure occurs.

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' :: 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' :: 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' :: 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' :: 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 ',')

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

Combine two alternatives.

endOfInput :: 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.

# Running parsers

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

Run a parser and return its result.

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)

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

Run a parser and print its result to standard output.

## Result conversion

maybeResult :: Result r -> Maybe r #

Convert a `Result` value to a `Maybe` value.

eitherResult :: Result r -> Either String r #

Convert a `Result` value to an `Either` value.