| > class PO a where | > (|=3D) :: a -> a -> Bool | > | > class Num a =3D> SemiRing a | > | > class SemiRing a =3D> CSemiRing a | > | > instance (Bounded a, Enum a, SemiRing a) =3D> PO a where | > a |=3D b | > =3D or [ a + c =3D=3D b | c <- boundedEnumFrom minBound ] | > | > instance CSemiRing a =3D> PO a where | > a |=3D b =3D a + b =3D=3D b Perhaps this means that SemiRing and CSemiRing should be types: class PO a where (|=) :: a -> a -> Bool data Num a => SemiRing a = SemiRing a data Num a => CSemiRing a = CSemiRing a instance (Bounded a,Enum a) => PO (SemiRing a) where (SemiRing a) |= (SemiRing b) = SemiRing ( or [ a + c == b | c <- boundedEnumFrom minBound ] ) instance PO (CSemiRing a) where (CSemiRing a) |= (CSemiRing b) = CSemiRing ( a + b == b ) Regards, Keean