pipe dream haxe

gistfile1.hx

typedef Monad<M> = {
    static function bind<A,B>(a:M<A>, f:A->M<B>):M<B>;
    static function ret<A>(a:A):M<A>;
}

enum MaybeImpl<A> {
    mJust(a:A);
    mNothing);
}

abstract Maybe(MaybeImpl) from MaybeImpl to MaybeImpl {
    static function bind<A,B>(a:Maybe<A>, f:A->Maybe<B>):Maybe<B> {
        return switch (a) { case mJust(a): f(a); default: mNothing; };
    }
    static function ret<A>(a:A):Maybe<A> return mJust(a);
}

class Func {
    static function liftM<M:Monad<M>,A,B>(f:A->B):M<A>->M<B> {
        return function (m1:M<A>):M<B> {
            return M.bind(m1, function (a:A):M<B> return M.ret(f(a)));
        };
    }
}

class Main {
    static function main() {
        var add1 = function (a) return a+1;
        trace(liftM(add1)(mJust(10)); // mJust(11)
        trace(liftM(add1)(mNothing)); // mNothing       
    }
}