“Pattern matching” of algebraic type data constructors

Question

Let\'s consider a data type with many constructors:

data T = Alpha Int | Beta Int | Gamma Int Int | Delta Int

I want to write a function to che

Answer 1

Another possible way:

sameK x y = f x == f y
  where f (Alpha _)   = 0
        f (Beta _)    = 1
        f (Gamma _ _) = 2
        -- runtime error when Delta value encountered

A runtime error is not ideal, but better than silently giving the wrong answer.