Haskell Enum Comparison

Question

I've defined an enum:

data Direction = Clockwise | CounterClockwise deriving (Enum)

Variable 'direction' has type 'Direction'. When doing the following comparison:

direction == Clockwise

I'm getting this error:

  No instance for (Eq OrbitDirection) arising from a use of `=='
  In the expression: direction == Clockwise

Answer 1

This is as simple as it gets: add the Eq instance to the derived instances list:

data Direction = Clockwise | CounterClockwise deriving (Enum, Eq)