TJ said:

In the wikibook article here: http://en.wikibooks.org/wiki/Haskell/Understanding_monads, which really does an excellent job explaining things (nuclear waste woohoo!), I am stuck at the following code snippet:

container >>= fn = \st -> let (a, st2) = container st container2 = fn a in container2 st2

What stumps me is that (>>=) is supposed to return a container, but if we return (container2 st2) as in the code, then what we're really returning is the contents of the container!

Note the lambda abstraction (\st -> ...) at the beginning of the definition. This means that (container >>= fn) returns a *function* that maps an input state to the result of (container2 st2). It doesn't return the result of (container st2) directly.

So what would happen if we do this:

nuclearWasteInContainer >>= processTheWaste >>= thoroughProcessTheWaste

It seems to me that the second (>>=) in the above expression would have the arguments (nuclearWaste) and (nuclearWasteProcessor), when what it really expects are (Container nuclearWaste) and (nuclearWasteProcessor). So isn't something wrong with the definition of (>>=) above? Or am I missing something?

(I know the article says that the type for their supposed State monad at that point is not actually correct, and will be clarified further on, but that seems to be irrelevant to my question.)

TJ the forever noobie.