[Haskell-beginners] Seeking some clarification...

Daniel Fischer daniel.is.fischer at googlemail.com
Sun Jun 5 22:06:20 CEST 2011

On Sonntag, 5. Juni 2011, 21:43, Sean Charles wrote:
> I can see that the term 'action' is one I need 
> to use more in my head when thinking about monads...

Well, that doesn't fit all Monads either.
Action is great for IO, but not helpful for [] or Maybe.
There are several widely used pictures illustrating monads, each fits some 
better than others.

The monads-as-containers picture works great for [], Maybe (those really 
*are* containers) and some more or less related monads. It doesn't really 
work well for IO, State, Cont and some more or less related monads.

The monads-as-computations picture works great for Cont, State and some 
related monads, less for [], Maybe, IO (it does work for those too, just 
less well).

The problem is that Monad is a very general and abstract concept, capturing 
widely different things, which need not have anything except the Monad 
structure in common.

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