module SwirledChecker
where

import Pan

import GHC.Base
import GHC.Int
import GHC.Float

swirledChecker :: Frac -> ImageC
swirledChecker v = swirl v checker

checker :: ImageC
checker = condR checkerReg blueI redI

checkerReg :: Region
checkerReg (Pt x y) = even' (floor' x + floor' y)

swirledCheckerAnim :: Frac -> ImageC
swirledCheckerAnim v = swirledChecker v

effect :: UI DisplayFun
effect = do
   v <- makeSlider "Radius" (10,100) 30
   imageToDisplayFun $ swirledCheckerAnim v


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