module Control.Shortcut where
import Control.Applicative
import Data.Maybe
class Shortcutable s where
shortcut :: [s a] -> ([Maybe a] -> Bool) -> s [Maybe a]
shortcut_ :: (Functor s, Shortcutable s) => [s a] -> ([a] -> Bool) -> s [a]
shortcut_ as f = catMaybes <$> shortcut as (f . catMaybes)
shortcut2 :: (Functor s, Monad s, Shortcutable s) => [s a] -> [s b] -> ([Maybe a] -> [Maybe b] -> Bool) -> s ([Maybe a], [Maybe b])
shortcut2 as bs f = do
let stripEitherFst aes = map (fromLeft <$>) $ take (length as) aes
let stripEitherLst bes = map (fromRight <$>) $ drop (length as) bes
let f' abs = f (stripEitherFst abs) (stripEitherLst abs)
mabs <- shortcut ((map (Left <$>) as) ++ (map (Right <$>) bs)) f'
return (stripEitherFst mabs, stripEitherLst mabs)
shortcut2b :: (Functor s, Monad s, Shortcutable s) => [s a] -> s b -> ([Maybe a] -> Bool -> Bool) -> s ([Maybe a], Bool)
shortcut2b as b f = do
let f' as bs = f as (isJust $ head bs)
(as, bs) <- shortcut2 as [b] f'
return (as, isJust $ head bs)
fromLeft :: Either a b -> a
fromLeft (Right _) = error "Argument takes form 'Right _'"
fromLeft (Left x) = x
fromRight :: Either a b -> b
fromRight (Left _) = error "Argument takes form 'Left _'"
fromRight (Right x) = x