-- Orion, Haskell variant, parallel - MPradella, MMXII

-- other excercise (or other step of the same):
-- parallelize applySF1 and applySF2 defined in orion.hs

import Control.Parallel


data SafeFloat = SF Float Float Float deriving Show

valid :: SafeFloat -> SafeFloat
valid (SF x y z) | x == y = SF x x x
valid (SF x y z) | y == z = SF y y y
valid (SF x y z) | x == z = SF z z z
valid _ = error "unsafe"


instance Eq SafeFloat where 
  x == y = let SF vx _ _ = valid x
               SF vy _ _ = valid y
           in vx == vy

parapplySF1 f (SF x y z) = 
  let x' = f x
      y' = f y
      z' = f z
  in x' `par` y' `par` 
     (z' `pseq` valid (SF x' y' z'))
  
parapplySF2 f (SF x y z) (SF x' y' z') =
  let x'' = f x x'
      y'' = f y y'
      z'' = f z z'
  in x'' `par` y'' `par` 
     (z'' `pseq` valid (SF x'' y'' z''))


instance Num SafeFloat where 
  (+) = parapplySF2 (+)
  (-) = parapplySF2 (+)
  (*) = parapplySF2 (*)
  negate = parapplySF1 negate
  abs = parapplySF1 abs
  signum = parapplySF1 signum
  fromInteger x = let x' = fromInteger x
                  in SF x' x' x'