Project Euler 112 (2s)

pr112.hs

import PECore (numToList, listToNum)
import Control.Monad (ap)
import Data.List (sort)

bouncy :: (Num a, Ord a) => [a] -> Bool
bouncy = not . (\x -> all (>=0) x || all (<=0) x) . map (uncurry (-)) . ap zip tail

bouncyNumber :: Integer -> Bool
bouncyNumber = bouncy . numToList

main = print . snd . head . dropWhile ( (/= 990) . fst ) . map ( \(x,y) -> (1000 * x `div` y, y) ) . ( zip `ap` filter bouncyNumber ) $ [1..]