Re: Can Class do this?

[Saswat Anand]

Thanks a lot. It works great with Hugs.   But it has a small problem. I also want to be able to write   4 \+ fc :: CF fc \+ 4 :: CF ic \+ 4 :: IF 4 \+ fc \+ ic :: CIF   Well for that I did this, instance (Rational a) => Plus a CF CF where     --to support 4.0 \+ fc        f \+ g = \c -> (realToFrac f) \+ (g c)   I did not do :  instance Plus Float CF CF where ..  so that I don't have to write    (4::Float) \+ fc.   But it complains because, it violates functional dependency a b -> c. Is there any other way to avoid writing (4::Float) in this case.   Well I tried this:   (\+) :: (Lift a c, Lift b c) => a -> b -> (c -> Float) f \+ g = \x -> (lift f) x + (lift f) x   class Lift a b where  lift :: a -> (b -> Float)   instance Lift CF Char where  lift = id   instance Lift CF (Char,Integer) where  lift f = \(c,i) -> f c   instance Lift IF Integer where  lift = id   instance Lift IF (Char,Integer) where  lift f = \(c,i) -> f i   instance Lift CIF (Char,Integer) where  lift = id   But it does not take following: x :: CF x = cf \+ cf \+ cf Cannot justify constraints in explicitly typed binding *****Expresssion : x *****Type : CF *****Given Context : () *****Constraints : (Lift (a -> Float) Char, Lift (Char -> FLoat) a)   Thanks, Saswat