appar-0.1.8: A simple applicative parser

Safe Haskell | Safe-Inferred
Language | Haskell98

Text.Appar.String

Contents

- Documentation
  - Parser type

Description

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.

Synopsis

- type Parser = MkParser String
- (<*>) :: Applicative f => f (a -> b) -> f a -> f b
- pure :: Applicative f => a -> f a
- (*>) :: Applicative f => f a -> f b -> f b
- (<*) :: Applicative f => f a -> f b -> f a
- (<|>) :: Alternative f => f a -> f a -> f a
- some :: Alternative f => f a -> f [a]
- many :: Alternative f => f a -> f [a]
- (<$) :: Functor f => a -> f b -> f a
- (<**>) :: Applicative f => f a -> f (a -> b) -> f b
- (<$>) :: Functor f => (a -> b) -> f a -> f b
- satisfy :: Input inp => (Char -> Bool) -> MkParser inp Char
- char :: Input inp => Char -> MkParser inp Char
- string :: Input inp => String -> MkParser inp String
- choice :: [MkParser inp a] -> MkParser inp a
- option :: a -> MkParser inp a -> MkParser inp a
- skipMany :: MkParser inp a -> MkParser inp ()
- sepBy1 :: MkParser inp a -> MkParser inp b -> MkParser inp [a]
- manyTill :: MkParser inp a -> MkParser inp b -> MkParser inp [a]
- try :: MkParser inp a -> MkParser inp a
- data MkParser inp a = P {
  - runParser :: inp -> (Maybe a, inp)
  }
- space :: Input inp => MkParser inp Char
- class Eq inp => Input inp where
  - car :: inp -> Char
  - cdr :: inp -> inp
  - nil :: inp
  - isNil :: inp -> Bool
- parse :: Input inp => MkParser inp a -> inp -> Maybe a
- anyChar :: Input inp => MkParser inp Char
- oneOf :: Input inp => String -> MkParser inp Char
- noneOf :: Input inp => String -> MkParser inp Char
- alphaNum :: Input inp => MkParser inp Char
- digit :: Input inp => MkParser inp Char
- hexDigit :: Input inp => MkParser inp Char
- skipSome :: MkParser inp a -> MkParser inp ()

# Documentation

## Parser type

type Parser = MkParser String Source #

Parser synonym for `String`.

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

Sequential application.

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

#### Example

Expand

Used in combination with ``(<$>)``, ``(<*>)`` can be used to build a record.

    >>> data MyState = MyState {arg1 :: Foo, arg2 :: Bar, arg3 :: Baz}

    >>> produceFoo :: Applicative f => f Foo
    >>> produceBar :: Applicative f => f Bar
    >>> produceBaz :: Applicative f => f Baz

    >>> mkState :: Applicative f => f MyState
    >>> mkState = MyState <$> produceFoo <*> produceBar <*> produceBaz

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

Lift a value into the Structure.

#### Examples

Expand

    >>> pure 1 :: Maybe Int
    Just 1

    >>> pure 'z' :: [Char]
    "z"

    >>> pure (pure ":D") :: Maybe [String]
    Just [":D"]

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

Sequence actions, discarding the value of the first argument.

#### Examples

Expand

If used in conjunction with the Applicative instance for `Maybe`, you can chain Maybe computations, with a possible "early return" in case of `Nothing`.

    >>> Just 2 *> Just 3
    Just 3

    >>> Nothing *> Just 3
    Nothing

Of course a more interesting use case would be to have effectful computations instead of just returning pure values.

    >>> import Data.Char
    >>> import GHC.Internal.Text.ParserCombinators.ReadP
    >>> let p = string "my name is " *> munch1 isAlpha <* eof
    >>> readP_to_S p "my name is Simon"
    [("Simon","")]

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

Sequence actions, discarding the value of the second argument.

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

An associative binary operation

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

One or more.

#### Examples

Expand

    >>> some (putStr "la")
    lalalalalalalalala... * goes on forever *

    >>> some Nothing
    nothing

    >>> take 5 <$> some (Just 1)
    * hangs forever *

Note that this function can be used with Parsers based on Applicatives. In that case `some parser` will attempt to parse `parser` one or more times until it fails.

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

Zero or more.

#### Examples

Expand

    >>> many (putStr "la")
    lalalalalalalalala... * goes on forever *

    >>> many Nothing
    Just []

    >>> take 5 <$> many (Just 1)
    * hangs forever *

Note that this function can be used with Parsers based on Applicatives. In that case `many parser` will attempt to parse `parser` zero or more times until it fails.

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

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.

#### Examples

Expand

Perform a computation with `Maybe` and replace the result with a constant value if it is `Just`:

    >>> 'a' <$ Just 2
    Just 'a'
    >>> 'a' <$ Nothing
    Nothing

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

A variant of `<*>` with the types of the arguments reversed. It differs from ``flip` `(<*>)`` in that the effects are resolved in the order the arguments are presented.

#### Examples

Expand

    >>> (<**>) (print 1) (id <$ print 2)
    1
    2

    >>> flip (<*>) (print 1) (id <$ print 2)
    2
    1

    >>> ZipList [4, 5, 6] <**> ZipList [(+1), (*2), (/3)]
    ZipList {getZipList = [5.0,10.0,2.0]}

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

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

Expand

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)

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

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

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

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

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

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

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

`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 Source #

`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 () Source #

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

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

`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] Source #

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

try :: MkParser inp a -> MkParser inp a Source #

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

data MkParser inp a Source #

Constructors

P |

Fields

- runParser :: inp -> (Maybe a, inp)

  Getting the internal parser.

#### Instances

Instances details

Alternative (MkParser inp) Source # |
Instance details Defined in Text.Appar.Parser Methods empty :: MkParser inp a Source # (<|>) :: MkParser inp a -> MkParser inp a -> MkParser inp a Source # some :: MkParser inp a -> MkParser inp [a] Source # many :: MkParser inp a -> MkParser inp [a] Source #
Applicative (MkParser inp) Source # |
Instance details Defined in Text.Appar.Parser Methods pure :: a -> MkParser inp a Source # (<*>) :: MkParser inp (a -> b) -> MkParser inp a -> MkParser inp b Source # liftA2 :: (a -> b -> c) -> MkParser inp a -> MkParser inp b -> MkParser inp c Source # (*>) :: MkParser inp a -> MkParser inp b -> MkParser inp b Source # (<*) :: MkParser inp a -> MkParser inp b -> MkParser inp a Source #
Functor (MkParser inp) Source # |
Instance details Defined in Text.Appar.Parser Methods fmap :: (a -> b) -> MkParser inp a -> MkParser inp b Source # (<$) :: a -> MkParser inp b -> MkParser inp a Source #
Monad (MkParser inp) Source # |
Instance details Defined in Text.Appar.Parser Methods (>>=) :: MkParser inp a -> (a -> MkParser inp b) -> MkParser inp b Source # (>>) :: MkParser inp a -> MkParser inp b -> MkParser inp b Source # return :: a -> MkParser inp a Source #
MonadPlus (MkParser inp) Source # |
Instance details Defined in Text.Appar.Parser Methods mzero :: MkParser inp a Source # mplus :: MkParser inp a -> MkParser inp a -> MkParser inp a Source #
MonadFail (MkParser inp) Source # |
Instance details Defined in Text.Appar.Parser Methods fail :: String -> MkParser inp a Source #

space :: Input inp => MkParser inp Char Source #

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

class Eq inp => Input inp where Source #

The class for parser input.

Methods

car :: inp -> Char Source #

The head function for input

cdr :: inp -> inp Source #

The tail function for input

nil :: inp Source #

The end of input

isNil :: inp -> Bool Source #

The function to check the end of input

#### Instances

Instances details

Input ByteString Source # |
Instance details Defined in Text.Appar.Input Methods car :: ByteString -> Char Source # cdr :: ByteString -> ByteString Source # nil :: ByteString Source # isNil :: ByteString -> Bool Source #
Input ByteString Source # |
Instance details Defined in Text.Appar.Input Methods car :: ByteString -> Char Source # cdr :: ByteString -> ByteString Source # nil :: ByteString Source # isNil :: ByteString -> Bool Source #
Input String Source # |
Instance details Defined in Text.Appar.Input Methods car :: String -> Char Source # cdr :: String -> String Source # nil :: String Source # isNil :: String -> Bool Source #

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

Run a parser.

anyChar :: Input inp => MkParser inp Char Source #

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

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

`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 Source #

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 Source #

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

digit :: Input inp => MkParser inp Char Source #

Parses a digit. Returns the parsed character.

hexDigit :: Input inp => MkParser inp Char Source #

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

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

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