Sure, you can define your own type class like that: import Prelude hiding ((+), (-)) -- usual (+) and (-) shouldn't be here... import qualified Prelude as P -- but they still are accessible with a prefix class Group a where (+) :: a -> a -> a (-) :: a -> a -> a instance Group Integer where (+) = (P.+) (-) = (P.-) instance Group A where (+) a b = A (elem1 a + elem1 b) (elem2 a + elem2 b) -- works for elem1 and elem2 being of class Group - say, Integer's (-) a b = ... 22.11.2010 9:48, Magicloud Magiclouds пишет:
Hi, For example, I have a data A defined. Then I want to add (+) and (-) operators to it, as a sugar (compared to addA/minusA). But * or other stuff defined in class Num is meanless to A. So I just do: (+) :: A -> A -> A (+) a b = A (elem1 a + elem1 b) (elem2 a + elem2 b) -- I got errors here, for the (+) is ambiguous.
So, just wondering, does this way work in Haskell?