Text.Appar.String

Simple Applicative parser whose input is String. The usage is the same as parsec.

Parsec 3 provides features which Parsec 2 does not provide:

• Applicative style
• ByteString as input

But Haskell Platform includes Parsec 2, not Parsec 3. Installing Parsec 3 to Haskell Platform environment makes it mess. So, this library was implemented.

Documentation

Parser type

type Parser = MkParser String

Parser synonym for String.

Running parser

parse :: Input inp => MkParser inp a -> inp -> Maybe a

Run a parser.

Char parsers

char :: Input inp => Char -> MkParser inp Char

char c parses a single character c. Returns the parsed character.

anyChar :: Input inp => MkParser inp Char

This parser succeeds for any character. Returns the parsed character.

oneOf :: Input inp => String -> MkParser inp Char

oneOf cs succeeds if the current character is in the supplied list of characters cs. Returns the parsed character.

noneOf :: Input inp => String -> MkParser inp Char

As the dual of oneOf, noneOf cs succeeds if the current character not in the supplied list of characters cs. Returns the parsed character.

alphaNum :: Input inp => MkParser inp Char

Parses a letter or digit (a character between '0' and '9'). Returns the parsed character.

digit :: Input inp => MkParser inp Char

Parses a digit. Returns the parsed character.

hexDigit :: Input inp => MkParser inp Char

Parses a hexadecimal digit (a digit or a letter between 'a' and 'f' or 'A' and 'F'). Returns the parsed character.

space :: Input inp => MkParser inp Char

Parses a white space character (any character which satisfies isSpace) Returns the parsed character.

String parser

string :: Input inp => String -> MkParser inp String

string s parses a sequence of characters given by s. Returns the parsed string

Parser combinators

try :: MkParser inp a -> MkParser inp a

The parser try p behaves like parser p, except that it pretends that it hasn't consumed any input when an error occurs.

choice :: [MkParser inp a] -> MkParser inp a

choice ps tries to apply the parsers in the list ps in order, until one of them succeeds. Returns the value of the succeeding parser.

option :: a -> MkParser inp a -> MkParser inp a

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

skipMany :: MkParser inp a -> MkParser inp ()

skipMany p applies the parser p zero or more times, skipping its result.

skipSome :: MkParser inp a -> MkParser inp ()

skipSome p applies the parser p one or more times, skipping its result.

sepBy1 :: MkParser inp a -> MkParser inp b -> MkParser inp [a]

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

manyTill :: MkParser inp a -> MkParser inp b -> MkParser inp [a]

manyTill p end applies parser p zero or more times until parser end succeeds. Returns the list of values returned by p.

Applicative parser combinators

(<$>) :: Functor f => (a -> b) -> f a -> f b infixl 4

An infix synonym for fmap.

The name of this operator is an allusion to $. Note the similarities between their types:

 ($)  ::              (a -> b) ->   a ->   b
(<$>) :: Functor f => (a -> b) -> f a -> f b

Whereas $ is function application, <$> is function application lifted over a Functor.

Examples

Convert from a Maybe Int to a Maybe String using show:

>>> show <$> Nothing
Nothing
>>> show <$> Just 3
Just "3"

Convert from an Either Int Int to an Either Int String using show:

>>> show <$> Left 17
Left 17
>>> show <$> Right 17
Right "17"

Double each element of a list:

>>> (*2) <$> [1,2,3]
[2,4,6]

Apply even to the second element of a pair:

>>> even <$> (2,2)
(2,True)

(<$) :: Functor f => a -> f b -> f a infixl 4

Replace all locations in the input with the same value. The default definition is fmap . const, but this may be overridden with a more efficient version.

(<*>) :: Applicative f => f (a -> b) -> f a -> f b infixl 4

Sequential application.

A few functors support an implementation of <*> that is more efficient than the default one.

(*>) :: Applicative f => f a -> f b -> f b infixl 4

Sequence actions, discarding the value of the first argument.

(<*) :: Applicative f => f a -> f b -> f a infixl 4

Sequence actions, discarding the value of the second argument.

(<**>) :: Applicative f => f a -> f (a -> b) -> f b infixl 4

A variant of <*> with the arguments reversed.

(<|>) :: Alternative f => f a -> f a -> f a infixl 3

An associative binary operation

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

One or more.

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

Zero or more.

pure :: Applicative f => a -> f a

Lift a value.

Internals

data MkParser inp a

Constructors

P

Fields

• runParser :: inp -> (Maybe a, inp)

  Getting the internal parser.

Instances

Monad (MkParser inp)

Defined in Text.Appar.Parser

Methods

(>>=) :: MkParser inp a -> (a -> MkParser inp b) -> MkParser inp b

(>>) :: MkParser inp a -> MkParser inp b -> MkParser inp b

return :: a -> MkParser inp a

fail :: String -> MkParser inp a

Functor (MkParser inp)

Defined in Text.Appar.Parser

Methods

fmap :: (a -> b) -> MkParser inp a -> MkParser inp b

(<$) :: a -> MkParser inp b -> MkParser inp a

MonadFail (MkParser inp)

Defined in Text.Appar.Parser

Methods

fail :: String -> MkParser inp a

Applicative (MkParser inp)

Defined in Text.Appar.Parser

Methods

pure :: a -> MkParser inp a

(<*>) :: MkParser inp (a -> b) -> MkParser inp a -> MkParser inp b

liftA2 :: (a -> b -> c) -> MkParser inp a -> MkParser inp b -> MkParser inp c

(*>) :: MkParser inp a -> MkParser inp b -> MkParser inp b

(<*) :: MkParser inp a -> MkParser inp b -> MkParser inp a

Alternative (MkParser inp)

Defined in Text.Appar.Parser

Methods

empty :: MkParser inp a

(<|>) :: MkParser inp a -> MkParser inp a -> MkParser inp a

some :: MkParser inp a -> MkParser inp [a]

many :: MkParser inp a -> MkParser inp [a]

MonadPlus (MkParser inp)

Defined in Text.Appar.Parser

Methods

mzero :: MkParser inp a

mplus :: MkParser inp a -> MkParser inp a -> MkParser inp a

class Eq inp => Input inp where

The class for parser input.

Methods

car :: inp -> Char

The head function for input

cdr :: inp -> inp

The tail function for input

nil :: inp

The end of input

isNil :: inp -> Bool

The function to check the end of input

Instances

Input String

Defined in Text.Appar.Input

Methods

car :: String -> Char

cdr :: String -> String

nil :: String

isNil :: String -> Bool

Input ByteString

Defined in Text.Appar.Input

Methods

car :: ByteString -> Char

cdr :: ByteString -> ByteString

nil :: ByteString

isNil :: ByteString -> Bool

Input ByteString

Defined in Text.Appar.Input

Methods

car :: ByteString -> Char

cdr :: ByteString -> ByteString

nil :: ByteString

isNil :: ByteString -> Bool

satisfy :: Input inp => (Char -> Bool) -> MkParser inp Char

The parser satisfy f succeeds for any character for which the supplied function f returns True. Returns the character that is actually parsed.