[Haskell] Top-level <-

John Meacham wrote:

Now, my mdo proposal as written would have "hello" outputed exactly once at module start up time no matter what, whether x is demanded or not. it is equivalant to a program transformation that collects all the top level initializers and declarations, puts them all in a mdo block and runs it with the semantics explained in the fixIO paper. (with a deterministic, but partially undefined order)

What happens if you write the following? y <- f x <- .... let f = something depending on x Will it know to evaluate x before y, or is this not allowed? What about if the assignments to y and x occur in different modules? Will the RTS have to analyse the dependencies to work out which order to run the assignments in?`