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.Text.Lazy

Contents

- Running parsers
  - Result conversion

Description

Simple, efficient combinator parsing that can consume lazy `Text` strings, loosely based on the Parsec library.

This is essentially the same code as in the `Text` module, only with a `parse` function that can consume a lazy `Text` 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 `Text` parameters, and return strict `Text` results. Behind the scenes, strict `Text` values are still used internally to store parser input and manipulate it efficiently.

Synopsis

- data Result r
  - = Fail Text [String] String
  - | Done Text r
- scientific :: Parser Scientific
- data Number
  - = I !Integer
  - | D !Double
- takeWhile :: (Char -> Bool) -> Parser Text
- take :: Int -> Parser Text
- satisfy :: (Char -> Bool) -> Parser Char
- char :: Char -> Parser Char
- string :: Text -> Parser Text
- 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 :: (Char -> Bool) -> Parser ()
- match :: Parser a -> Parser (Text, a)
- space :: Parser Char
- double :: Parser Double
- rational :: Fractional a => Parser a
- decimal :: Integral a => Parser a
- hexadecimal :: (Integral a, Bits a) => Parser a
- signed :: Num a => Parser a -> Parser a
- type Parser = Parser Text
- compareResults :: (Eq i, Eq r) => IResult i r -> IResult i r -> Maybe Bool
- feed :: Monoid i => IResult i r -> i -> IResult i r
- satisfyWith :: (Char -> a) -> (a -> Bool) -> Parser a
- inClass :: String -> Char -> Bool
- notInClass :: String -> Char -> Bool
- skipWhile :: (Char -> Bool) -> Parser ()
- scan :: s -> (s -> Char -> Maybe s) -> Parser Text
- runScanner :: s -> (s -> Char -> Maybe s) -> Parser (Text, s)
- takeWhile1 :: (Char -> Bool) -> Parser Text
- takeTill :: (Char -> Bool) -> Parser Text
- (<?>) :: 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
- anyChar :: Parser Char
- notChar :: Char -> Parser Char
- peekChar :: Parser (Maybe Char)
- peekChar' :: Parser Char
- digit :: Parser Char
- stringCI :: Text -> Parser Text
- skipSpace :: Parser ()
- (.*>) :: Text -> Parser a -> Parser a
- (<*.) :: Parser a -> Text -> Parser a
- endOfLine :: Parser ()
- isEndOfLine :: Char -> Bool
- isHorizontalSpace :: Char -> Bool
- number :: Parser Number
- letter :: Parser Char
- asciiCI :: Text -> Parser Text
- takeText :: Parser Text
- takeLazyText :: Parser Text
- parse :: Parser a -> Text -> Result a
- parseOnly :: Parser a -> Text -> Either String a
- parseTest :: Show a => Parser a -> Text -> IO ()
- maybeResult :: Result r -> Maybe r
- eitherResult :: Result r -> Either String r

# Documentation

data Result r #

The result of a parse.

Constructors

Fail Text [String] String | The parse failed. The `Text` 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 Text r | The parse succeeded. The `Text` 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.Text.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.Text.Lazy Methods rnf :: Result r -> () #
Show r => Show (Result r) # |
Instance details Defined in Data.Attoparsec.Text.Lazy Methods showsPrec :: Int -> Result r -> ShowS # show :: Result r -> String # showList :: [Result r] -> ShowS #

scientific :: Parser Scientific #

Parse a scientific number.

The syntax accepted by this parser is the same as for `double`.

data Number #

A numeric type that can represent integers accurately, and floating point numbers to the precision of a `Double`.

Note: this type is deprecated, and will be removed in the next major release. Use the `Scientific` type instead.

Constructors

I !Integer |
D !Double |

#### Instances

Instances details

NFData Number # |
Instance details Defined in Data.Attoparsec.Number Methods rnf :: Number -> () #
Data Number # |
Instance details Defined in Data.Attoparsec.Number Methods gfoldl :: (forall d b. Data d => c (d -> b) -> d -> c b) -> (forall g. g -> c g) -> Number -> c Number # gunfold :: (forall b r. Data b => c (b -> r) -> c r) -> (forall r. r -> c r) -> Constr -> c Number # toConstr :: Number -> Constr # dataTypeOf :: Number -> DataType # dataCast1 :: Typeable t => (forall d. Data d => c (t d)) -> Maybe (c Number) # dataCast2 :: Typeable t => (forall d e. (Data d, Data e) => c (t d e)) -> Maybe (c Number) # gmapT :: (forall b. Data b => b -> b) -> Number -> Number # gmapQl :: (r -> r' -> r) -> r -> (forall d. Data d => d -> r') -> Number -> r # gmapQr :: forall r r'. (r' -> r -> r) -> r -> (forall d. Data d => d -> r') -> Number -> r # gmapQ :: (forall d. Data d => d -> u) -> Number -> [u] # gmapQi :: Int -> (forall d. Data d => d -> u) -> Number -> u # gmapM :: Monad m => (forall d. Data d => d -> m d) -> Number -> m Number # gmapMp :: MonadPlus m => (forall d. Data d => d -> m d) -> Number -> m Number # gmapMo :: MonadPlus m => (forall d. Data d => d -> m d) -> Number -> m Number #
Num Number # |
Instance details Defined in Data.Attoparsec.Number Methods (+) :: Number -> Number -> Number # (-) :: Number -> Number -> Number # (*) :: Number -> Number -> Number # negate :: Number -> Number # abs :: Number -> Number # signum :: Number -> Number # fromInteger :: Integer -> Number #
Fractional Number # |
Instance details Defined in Data.Attoparsec.Number Methods (/) :: Number -> Number -> Number # recip :: Number -> Number # fromRational :: Rational -> Number #
Real Number # |
Instance details Defined in Data.Attoparsec.Number Methods toRational :: Number -> Rational #
RealFrac Number # |
Instance details Defined in Data.Attoparsec.Number Methods properFraction :: Integral b => Number -> (b, Number) # truncate :: Integral b => Number -> b # round :: Integral b => Number -> b # ceiling :: Integral b => Number -> b # floor :: Integral b => Number -> b #
Show Number # |
Instance details Defined in Data.Attoparsec.Number Methods showsPrec :: Int -> Number -> ShowS # show :: Number -> String # showList :: [Number] -> ShowS #
Eq Number # |
Instance details Defined in Data.Attoparsec.Number Methods (==) :: Number -> Number -> Bool # (/=) :: Number -> Number -> Bool #
Ord Number # |
Instance details Defined in Data.Attoparsec.Number Methods compare :: Number -> Number -> Ordering # (<) :: Number -> Number -> Bool # (<=) :: Number -> Number -> Bool # (>) :: Number -> Number -> Bool # (>=) :: Number -> Number -> Bool # max :: Number -> Number -> Number # min :: Number -> Number -> Number #

takeWhile :: (Char -> Bool) -> Parser Text #

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 character 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 Text #

Consume exactly `n` characters of input.

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

The parser `satisfy p` succeeds for any character for which the predicate `p` returns `True`. Returns the character that is actually parsed.

    digit = satisfy isDigit
        where isDigit c = c >= '0' && c <= '9'

char :: Char -> Parser Char #

Match a specific character.

string :: Text -> Parser Text #

`string s` parses a sequence of characters 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 :: (Char -> Bool) -> Parser () #

The parser `skip p` succeeds for any character for which the predicate `p` returns `True`.

    skipDigit = skip isDigit
        where isDigit c = c >= '0' && c <= '9'

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

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

space :: Parser Char #

Parse a space character, as recognised by `isSpace`.

double :: Parser Double #

Parse a `Double`.

This parser accepts an optional leading sign character, followed by at most one decimal digit. The syntax is similar to that accepted by the `read` function, with the exception that a trailing `'.'` is consumed.

### Examples

These examples use this helper:

    r :: Parser a -> Text -> Result a
    r p s = feed (parse p s) mempty

Examples with behaviour identical to `read`, if you feed an empty continuation to the first result:

    r double "3"     == Done "" 3.0
    r double "3.1"   == Done "" 3.1
    r double "3e4"   == Done "" 30000.0
    r double "3.1e4" == Done "" 31000.0
    r double "3e"    == Done "e" 3.0

Examples with behaviour identical to `read`:

    r double ".3"    == Fail ".3" _ _
    r double "e3"    == Fail "e3" _ _

Example of difference from `read`:

    r double "3.foo" == Done "foo" 3.0

This function does not accept string representations of "NaN" or "Infinity".

rational :: Fractional a => Parser a #

Parse a rational number.

The syntax accepted by this parser is the same as for `double`.

Note: this parser is not safe for use with inputs from untrusted sources. An input with a suitably large exponent such as `"1e1000000000"` will cause a huge `Integer` to be allocated, resulting in what is effectively a denial-of-service attack.

In most cases, it is better to use `double` or `scientific` instead.

decimal :: Integral a => Parser a #

Parse and decode an unsigned decimal number.

hexadecimal :: (Integral a, Bits a) => Parser a #

Parse and decode an unsigned hexadecimal number. The hex digits `'a'` through `'f'` may be upper or lower case.

This parser does not accept a leading `"0x"` string.

signed :: Num a => Parser a -> Parser a #

Parse a number with an optional leading `'+'` or `'-'` sign character.

type Parser = Parser Text #

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.

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

The parser `satisfyWith f p` transforms a character, and succeeds if the predicate `p` returns `True` on the transformed value. The parser returns the transformed character that was parsed.

inClass :: String -> Char -> Bool #

Match any character 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 -> Char -> Bool #

Match any character not in a set.

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

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

scan :: s -> (s -> Char -> Maybe s) -> Parser Text #

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 character 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 character 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 -> Char -> Maybe s) -> Parser (Text, s) #

Like `scan`, but generalized to return the final state of the scanner.

takeWhile1 :: (Char -> Bool) -> Parser Text #

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 character of input: it will fail if the predicate never returns `True` or if there is no input left.

takeTill :: (Char -> Bool) -> Parser Text #

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 character 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.

(<?>) 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.

anyChar :: Parser Char #

Match any character.

notChar :: Char -> Parser Char #

Match any character except the given one.

peekChar :: Parser (Maybe Char) #

Match any character, 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.

peekChar' :: Parser Char #

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

digit :: Parser Char #

Parse a single digit, as recognised by `isDigit`.

stringCI :: Text -> Parser Text #

Deprecated: this is very inefficient, use asciiCI instead

Satisfy a literal string, ignoring case.

Note: this function is currently quite inefficient. Unicode case folding can change the length of a string ("ß" becomes "ss"), which makes a simple, efficient implementation tricky. We have (for now) chosen simplicity over efficiency.

skipSpace :: Parser () #

Skip over white space.

(.*>) :: Text -> Parser a -> Parser a #

Deprecated: This is no longer necessary, and will be removed. Use `*>` instead.

Obsolete. A type-specialized version of `*>` for `Text`. Use `*>` instead.

(<*.) :: Parser a -> Text -> Parser a #

Deprecated: This is no longer necessary, and will be removed. Use `<*` instead.

Obsolete. A type-specialized version of `<*` for `Text`. Use `*>` instead.

endOfLine :: Parser () #

Match either a single newline character `'\n'`, or a carriage return followed by a newline character `"\r\n"`.

isEndOfLine :: Char -> Bool #

A predicate that matches either a carriage return `'\r'` or newline `'\n'` character.

isHorizontalSpace :: Char -> Bool #

A predicate that matches either a space `' '` or horizontal tab `'\t'` character.

number :: Parser Number #

Deprecated: Use `scientific` instead.

Parse a number, attempting to preserve both speed and precision.

The syntax accepted by this parser is the same as for `double`.

This function does not accept string representations of "NaN" or "Infinity".

letter :: Parser Char #

Parse a letter, as recognised by `isAlpha`.

asciiCI :: Text -> Parser Text #

Satisfy a literal string, ignoring case for characters in the ASCII range.

takeText :: Parser Text #

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

takeLazyText :: Parser Text #

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

# Running parsers

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

Run a parser and return its result.

parseOnly :: Parser a -> Text -> 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 -> Text -> 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.