Safe Haskell	Safe-Inferred
Language	Haskell2010

Text.LambdaOptions.Parseable

Synopsis

Documentation

class Parseable a where Source

Class describing parseable values. Much like the Read class.

Methods

parse :: [String] -> (Maybe a, Int) Source

Given a sequence of strings, parse returns Nothing and the number of strings consumed if the parse failed. Otherwise, parse returns Just the parsed value and the number of strings consumed.

Element-wise, an entire string must be parsed in the sequence to be considered a successful parse.

Instances

Parseable Char	Parses a single character string.
Parseable Float	Parses a `Float` using its `Read` instance.
Parseable Int	Parses an `Int` using its `ReadBounded` instance.
Parseable Integer	Parses an `Integer` using its `Read` instance.
Parseable Word	Parses a `Word` using its `ReadBounded` instance.
Parseable String	Identity parser. Ex: @parse "abc" == (Just "abc", 1)
Parseable ()
Parseable a => Parseable (Maybe a)	Greedily parses a single argument or no argument. Never fails.
Parseable a => Parseable (List a)	Greedily parses arguments item-wise. Never fails. Example: `parse (words "5 67 NaN") == (Just (List [5,67]), 2)`
(Parseable a, Parseable b) => Parseable (a, b)
(Parseable a, Parseable b, Parseable c) => Parseable (a, b, c)

simpleParse :: (String -> Maybe a) -> [String] -> (Maybe a, Int) Source

Turns a parser of a single string into a parser suitable for a Parseable instance.

Useful for implementing a Parseable for a type with a Read instance by supplying readMaybe to this function.

Note: The string is not tokenized in any way before being passed into the input parser.

repeatedParse :: Parseable a => Int -> [String] -> (Maybe [a], Int) Source

Repeatedly applies parse the given number of times, accumulating the results.

Useful for implementing new parsers.

Example:

data Point = Point Float Float Float

instance Parseable Point where
    parse strs = case repeatedParse 3 strs of
        (Just [x,y,z], n) -> (Just (Point x y z), n)`
        (Nothing, n) -> (Nothing, n)