On Saturday 03 July 2010 3:57:34 pm Thomas Hartman wrote:
> When I load up Control.Applicative in ghci and try, eg
>
> many [1,2] or many (Just 1) or some [1,2] or some (Just 1)
>
> this never returns.
>
> What are the practical uses of these combinators, or for using the
> Alternative class in general?
import Control.Applicative
import Control.Monad
import Control.Monad.State
type M = StateT [Int] []
pluck :: M Int
pluck = do l <- get
case l of
[] -> empty
x:xs -> put xs *> pure x
{-
*Main> runStateT (many pluck) [1..4]
[([1,2,3,4],[]),([1,2,3],[4]),([1,2],[3,4]),([1],[2,3,4]),([],[1,2,3,4])]
-}
-- Dan
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