W is equivalent to join, yes. M can't be typed in Haskell (without newtypes), so there's no real equivalent. Of course they're not really useful for programmin

W is equivalent to join, yes. M can't be typed in Haskell (without newtypes), so there's no real equivalent. Of course they're not really useful for programming; they're more interesting as a compilation target, formal reasoning, and some fun puzzles.