Richard O'Keefe:

    class (Eq a, Show a) => Num a
      where (+) (-) (*) negate abs signum fromInteger

where functions are for good reason not members of Eq or Show.

This is an old song, changed several times. I have no intention to discuss, but please, Richard O'Keefe:
WHICH GOOD REASONS??

Thank you.

Jerzy Karczmarczuk