IFPHの12章のプログラムの動かし方 ref: http://qiita.com/nnabeyang/items/f01103bc4487a5cc202c

file0.txt

ghci> :l Examples
ghci> ex6

MyParseLib.lhs

> import Data.Char

> instance Functor Parser where
>   -- map f p = MkP g
>   fmap f p = MkP g
>             where g s = [(f x, s') | (x,s') <- papply p s]

> alphanum :: Parser Char
> -- alphanum = sat isAlphaum
> alphanum = sat isAlphaNum

Utilities.lhs

> partitions :: Int -> [a] -> [[[a]]]
> partitions 0 []     = [[]]
> partitions n []     = []
> partitions 0 _      = []
> partitions n (x:xs) = [[x]:yss | yss <- partitions (n-1) xs] ++
>      [(x:ys):yss | ys:yss <- partitions n xs]