[Haskell-cafe] Join a transformer

[Daniel Díaz Casanueva]

+1 on adding this to transformers.

2018-04-09 14:45 GMT+02:00 Ross Paterson <R.Paterson at city.ac.uk>:

> On Thu, Mar 14, 2013 at 05:24:23AM +0200, Michael Snoyman wrote:
> >    I'm wondering if this pattern exists and has a name. We have the
> >    concept of joining a Monad:
> >    join :: Monad m => m (m a) -> ma
> >    How about joining a monad transformer?
> >    joinT :: (Monad m, MonadTrans t) => t (t m) a -> t m a
>
> This is a monad in the category of monads.  Moggi discusses them in
> "An Abstract View of Programming Languages", including which transformers
> have joinT.  I was thinking of adding the class to the transformers
> package.
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