Hi all, A simple question for advanced Haskellers, but I still have some problems bending my mind over it. Example: I have some function, that can return multiple results. Currently I need only the first one, but in the spirit of NotJustMaybe, I try to be as general as possible. If I code it like this: reduction :: (MonadPlus m) => [Rule] -> Expr -> m Expr reduction expr = do rule <- rules reduction rule expr Variable m gets unified with []. But I want m to stay as general as possible here. This version works, but I somehow do not like the "smell" of it reduction expr = do let listmonad = do rule <- rules reduction rule expr msum (map return listmonad) Is there a better way how to "embed" MonadPlus in other "MonadPlus"? -- Gracjan