Re: [Haskell-cafe] Join a transformer

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.