Haskell Polymorphism

Question

data Set a = Set [a]

-- Example 1
instance (Eq a, Ord a)  => Eq (Set a) where 
  (Set xs) == (Set ys) = (sort xs) == (sort ys) 

-- Example 2 
instance (Eq a, Ord a)  => Eq (Set a) where   
  (==) = eqSet

eqSet (Set xs) (Set ys) = (sort xs) == (sort ys)

Example 1 and 2 are different ways of overriding the '==' for equality testing for the Set datatype. I'd like to know which way is preferable and why?

Thanks.

Answer 1

There is no difference aside from the existence of the eqSet identifier and inlining concerns which can be solved with an {-# INLINE eqSet #-} pragma. My personal preference would be to use the inlined version since the separate definition doesn't provide any value, but I don't think it matters much.