[Haskell-cafe] Monad Imparative Usage Example

[Kaveh Shahbazian]

Thanks All
This is about my tries to understand monads and handling state - as
you perfectly know - is one of them. I have understood a little about
monads but that knowledge does not satidfy me. Again Thankyou

On 8/2/06, Duncan Coutts <duncan.coutts at worc.ox.ac.uk> wrote:
> On Wed, 2006-08-02 at 13:26 +0330, Kaveh Shahbazian wrote:
> > Haskell is the most powerfull and interesting "thing" I'v ever
> > encountered in IT world. But with an imparative background and lack of
> > understanding (because of any thing include that maybe I am not that
> > smart) has brought me problems. I know this is an old issue. But
> > please help it.
> > Question : Could anyone show me a sample of using a monad as a
> > statefull variable?
> > For example see this code in C# :
> > //
> > public class Test
> > {
> >     int var;
> >     static void Fun1() { var = 0; Console.Write(var); }
> >     static void Fun2() { var = var + 4; Console.Write(var); }
> >     static void Main() { Fun1(); Fun2(); var = 10; Console.Write("var
> > = " + var.ToString()); }
> > }
> > //
> > I want to see this code in haskell.
>
> As other people have noted, you probably don't want to to see this code
> in Haskell. It's possible to translate stateful code in a 1-1 style but
> that's not really the point. You'll not get much of the advantages of
> the language if you do that.
>
> You can certainly use console IO etc but for your object containing
> mutable state, well in a functional style you'd simply not do that and
> solve the problem in a different way.
>
> That's why you see the code people have suggested as translations are
> bigger than the code you started with, because the language is not
> naturally imperative.
>
> So the trick is to solve your problem in Haskell, not translate your
> imperative solution to Haskell.
>
> Duncan
>
>