module Checker
where

-- library imports
import GHC.Base
import GHC.Int
import GHC.Float

import Pan

checker :: ImageC
checker (Pt x y) = if even' (floor' x + floor' y) then black else white

effect :: UI DisplayFun
effect = animToDisplayFun $ liftToAnim checker

floor' :: Float -> Int
floor' (F# f) = case ltFloat# f 0.0# of
                 True -> I# ((float2Int# f) -# 1#)
                 _    -> I# (float2Int# f)

even' :: Int -> Bool
even' (I# n) =
  case modInt# n 2#  of
       0# -> True
       _  -> False