Haskell Enum Comparison

Question

I defined the enumeration:

data Direction = Clockwise | CounterClockwise deriving (Enum)

The variable 'direction' is of type 'Direction'. When performing the following comparison:

direction == Clockwise

I get this error:

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

Answer 1

It's as simple as it gets: add the instance Eqto the list of derived instances:

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