Is it a bad idea to define some, but not all methods of a type class in Haskell? -

Is it a bad idea to define some, but not all methods of a type class in Haskell? -

want this:

data point = point double double instance num point (point ax ay) + (point bx by) = point (ax + bx) (ay + by) negate (point ax ay) = point (negate ax) (negate ay)

syntastic doesn't it. wants me define methods *, abs, frominteger , signum.

what's recommended way me + , - operator defined point without taking on rest?

also, define different kinds of scalar , vector multiplication double * point or point * point in cross-product or dot-product sense. type scheme isn't friend here, right?

and + operator can think of? why not +/? or +.? what's wrong them?

yes, leaving members of class unimplemented bad form.

as lastly resort, define own typeclass this

import prelude hiding ((+)) import qualified prelude ((+)) class plus c (+) :: c -> c -> c instance plus double (+) = prelude.(+) instance plus point point x1 y1 + point x2 y2 = point (x1 + x2) (y1 + y2)

haskell