Parameter Make2.X

Multi parameter monad. The second parameter gets unified across all the computation. This is used to encode monads working on a multi parameter data structure like (('a,'b) result).

The following identities ought to hold (for some value of =):

• return x >>= f = f x
• t >>= fun x -> return x = t
• (t >>= f) >>= g = t >>= fun x -> (f x >>= g)

Note: >>= is the infix notation for bind)