Monads in mercury

:- module monad.

:- interface.

:- type monad(M, T) ---> monad(M, T).

:- typeclass monad(M) where [

    % (>>=) :: m a -> (a -> m b) -> m b
    func bind(
        monad(M, T1),
        func(T1) = monad(M, T2)
    ) = monad(M, T2),

    % return :: a -> Maybe a
    func return(T) = monad(M, T)

].