+data Tetrahedron =
+ Tetrahedron { fv :: FunctionValues,
+ v0 :: Point,
+ v1 :: Point,
+ v2 :: Point,
+ v3 :: Point,
+ precomputed_volume :: Double,
+
+ -- | Between 0 and 23; used to quickly determine which
+ -- tetrahedron I am in the parent 'Cube' without
+ -- having to compare them all.
+ number :: Int
+ }
+ deriving (Eq)
+
+
+instance Arbitrary Tetrahedron where
+ arbitrary = do
+ rnd_v0 <- arbitrary :: Gen Point
+ rnd_v1 <- arbitrary :: Gen Point
+ rnd_v2 <- arbitrary :: Gen Point
+ rnd_v3 <- arbitrary :: Gen Point
+ rnd_fv <- arbitrary :: Gen FunctionValues
+ rnd_no <- choose (0,23)
+
+ -- We can't assign an incorrect precomputed volume,
+ -- so we have to calculate the correct one here.
+ let t' = Tetrahedron rnd_fv rnd_v0 rnd_v1 rnd_v2 rnd_v3 0 rnd_no
+ let vol = volume t'
+ return (Tetrahedron rnd_fv rnd_v0 rnd_v1 rnd_v2 rnd_v3 vol rnd_no)
+