Stream.hs

{-#LANGUAGE MultiParamTypeClasses, FunctionalDependencies, FlexibleInstances #-}
module Text.Parcom.Stream
where

class Stream s t | s -> t where
    peek :: s -> t
    atEnd :: s -> Bool
    consume :: s -> s
    pop :: s -> (t, s)
    consume = snd . pop
    pop s = (peek s, consume s)

instance Stream [a] a where
    peek = head
    atEnd = null
    consume = tail

class Token t where
    isLineDelimiter :: t -> Bool

instance Token Char where
    isLineDelimiter '\n' = True
    isLineDelimiter _ = False

class Listish s t | s -> t where
    toList :: s -> [t]
    fromList :: [t] -> s

instance Listish [a] a where
    toList = id
    fromList = id

class Textish s where
    peekChar :: s -> (Maybe Char, Int)

instance Textish [Char] where
    peekChar [] = (Nothing, 0)
    peekChar (c:[]) = (Just c, 1)