Project Euler 206 (1 s)

pr206.hs

import Data.List (find)
import Control.Monad (replicateM)
import Data.Maybe (fromJust)
import Numeric (showFFloat)

isSquare :: Integer -> Bool
isSquare x = x'*x' == x
    where x' = truncate $ sqrt (fromIntegral x :: Double)

sew :: [Integer] -> Integer
sew = foldl1 ((+).(*10)) . (++ [9,0,0]) . concatMap (uncurry ((. return) . (:))) . zip [1..]

main = print $ showFFloat (Just 0) (sqrt . fromIntegral . fromJust . find isSquare . map sew $ replicateM 8 [9,8..0]) ""