Re: [Haskell-cafe] State monad strictness - how?

...how would one know that State is lazy and StateT is strict? I don't see that in the Haddock documentation.

You're right, it is not in the docs. I don't think anyone would have planned it that way. StateT is strict only because there happens to be a line in a do-expression that looks like: (a, s') <- runStateT m s The tuple pattern-match causes the strictness. That appears accidental, so it seems to be just an honest bug. Regards, Yitz