testfunc = do r <- newSTRef ('x',0) foo r bar r (c,n) <- readSTRef r return n
Jorge Adriano
Yeap, I could do it like this myself :) The whole problem is with passing the 'r' as a parameter, which is precisly what I'm trying to avoid.
I agree with you. My work-around is then to define foo and bar locally to testfunc, in the scope of r: testfunc = do r <- newSTRef ('x',0) let foo = do (c,n) <- readSTRef r writeSTRef r ('a', n+1) bar = do (c,n) <- readSTRef r writeSTRef r (c,n+2) foo bar (c,n) <- readSTRef r return n But if this looks like unsatisfactory (it does to me, too), perhaps you have to go back to DIY monads. DIY monads are good when: you fix the state variables, you don't want to mention them in subprogram parameters. The ST monad is good when: you create more state variables on the fly, you use mutable arrays, you don't want to write your own monad and put/get commands.