Is join useful for every monad?

[Henning Thielemann]

On Mon, 14 Oct 2019, Georgi Lyubenov wrote:

> Other examples (subjectively of course) of such things are (<*>) which 
> allows you to implement liftA{2,3,..} and mfix, which allows you to have 
> recursive bindings in a do block.

Other example: We have

   liftM2 :: (a -> b -> c) -> m a -> m b -> m c

but what can we do, if we need:

   liftM2' :: (a -> b -> m c) -> m a -> m b -> m c

?


We could just do:

   join $ liftM2 f ma mb