-- Some tests on floats.

import Test.Prop

-- Property: the addition operator is commutative
addIsCommutative :: Float -> Float -> Prop
addIsCommutative x y = x + y -=- y + x

-- Property: the addition operator is almost associative due to rounding errors
addIsAssociative :: Float -> Float -> Float -> Prop
addIsAssociative x y z = always (almostEqual ((x + y) + z) (x + (y + z)))

almostEqual :: Float -> Float -> Bool
almostEqual x y = absf (x - y) < 0.00001
 where
  absf x = if x < 0 then 0.0 - x else x