[Haskell-cafe] Stacked return

Dmitry Bogatov KAction at gnu.org
Sat Nov 23 17:30:23 UTC 2013

> Perhaps you just want monad transformers [1, 2]. If you're not familiar
> with them, you should probably read [3].
> With transformers you'd be able to do this (and more):
> $ return 2 :: IO Int
> $ return 2 :: ListT Maybe Int   -- this works like Maybe [Int]
> $ return 2 :: MaybeT [] Int     -- this works like [Maybe Int]

In fact, I read and used transformers a bit. If I understand correctly,
I can only do such things for monads, supported by transformers. So,

I cant get (return 2) :: MyWierdMonad (MyAnotherMonad 2)

Yes, I know, it have little practical use, but I am insterested about
teoretical part of question, magic of ghc.

Best regards, Dmitry Bogatov <KAction at gnu.org>,
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