Magicloud Magiclouds
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?
The Monoid class represents monoids, but it has no inversion function, so you can only express addition with it. Also its member function names are unfortunate for almost anything other than lists. Anyway, whenever your set is at most countably infinite, you can always make sense of the multiplication function. Note that multiplication is not required to be commutative. In the worst case you can leave it undefined: instance Num A where _ * _ = error "Cannot multiply A values" Greets, Ertugrul -- nightmare = unsafePerformIO (getWrongWife >>= sex) http://ertes.de/