I doubt it's an issue of being too stupid. If you come from more
traditional languages, then Haskell requires that to rewire your brain
to think in Haskell. It's very different. It appears hard because
there is a lot of work to re-learning things you thought you knew.
As for combining two state monads, is there a reason you cannot
combine them into one large state?
It looks what you are doing is:
importantFunction initialFoo initialBar =
let foo = execState modifiesFoo initialFoo
in (foo, execState (modifiesBar foo) initialBar)
Which would have the type signature you are expecting and wouldn't
need to be monadic.
Drew Haven
drew.haven@gmail.com
On Wed, Jun 23, 2010 at 2:10 PM, Jordan Cooper
I have two pieces of state I'm managing: type FooState = State Foo Foo type BarState = State Bar Bar
There is a bit of interplay between them, and I want a function that does something like: importantFunction :: Foo -> Bar -> (Foo, Bar)
The problem is, >>= only works when I'm chaining all of the same type of state. So I can't do: modifiesFoo >>= \foo -> modifiesBar foo >>= \bar -> return (foo, bar)
So how do I get the results of both modifications back? I hope that makes sense. Programming in Haskell is proving to be very difficult; I once again fear I'm too stupid. _______________________________________________ Beginners mailing list Beginners@haskell.org http://www.haskell.org/mailman/listinfo/beginners