On Mar 19, 2012 11:40 AM, "Ozgur Akgun" <ozgurakgun@gmail.com> wrote:
> {-# LANGUAGE FlexibleInstances #-}
>
> instance Num a => Num (a -> a) where

You don't want (a -> a) there.  You want (b -> a).  There is nothing about this that requires functions to come from a numeric type, much less the same one.

--
Chris Smith