NoEq.hs

module NoEq where

If you want to derive Eq for some big datatype that contains something that does not allow equality, you can wrap it in NoEq. For example you can use NoEq (Int->Int) instead of (Int->Int) as an argument to a constructor.

newtype NoEq a = N a

instance Eq  (NoEq a) where _ == _ = True
instance Ord (NoEq a) where compare _ _ = EQ

instance Show a => Show (NoEq a) where showsPrec n (N x) = showsPrec n x