[tree_of_item]

> How does not having static typing prevent you from abstracting over monads?

They were probably talking about the way Haskell can figure out which monad you're in through type inference. As an example, `return :: a -> m a` dispatches on the type of the function's return value, which doesn't map cleanly to a dynamically typed implementation. You need to be explicit about the monad you're in if you don't have the compiler helping you out.

[dragonwriter]

That's true (and, heck, its true even of many static languages that support monads; that feature of Haskell is due to its better-than-most type inference, not just having static typing), but I don't see how that limits the capacity for abstraction. Certainly, you may need an additional explicit parameter in some cases rather than effectively implicitly supplying information via type inference, but that doesn't change the level of abstraction.