Definition of CompassDirection and some operations over it:
data CompassDirection = West | NorthWest | North | NorthEast | East | SouthEast | South | SouthWest | Centre -- instances: Eq, Ord, Ix, Text northOrSouth :: CompassDirection -> Bool eastOrWest :: CompassDirection -> Bool diametricDir :: CompassDirection -> CompassDirection simplifyDir :: CompassDirection -> [CompassDirection]