[jpfed]

Other replies talk about how Promises can be implemented as monads. Aside from that, you can come up with your own, too.

One monad that I occasionally use is something I'll call "Tracked". For "return" (when we make a new instance of the monad) we store a pair (initialValue, initialValue). For "bind" (when we act on what's in the monad) we only ever touch the second value in the pair, returning (initialValue, transformedValue).

That way, you can know where this piece of data came from. I've gotten a lot of mileage out of Tracked<Result<T>>: when one of your Results is an exception, then you can check what piece of data ended up triggering that exception. Yes, you could do this without the Tracked monad, but doing it monadically means that most of your functions don't need to know or care about tracking the initial data; you can just Apply those simpler functions and the Tracked instance will do it for you.