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static fields?
f#

In C#, if I'd like to define a static member, I can do the following

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public class C
{
   public static int I;
   static C() { I = 5; }
}

How do I do that in F#? My motivations (hiding a memoization cache in a class) may not be pure, but I also wonder if I am just stumbling on syntax

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type C =
   static val I:int

Isn't happy ("syntax error"), though it appears quite clear from the F# manual that this is not allowed anyway. Why?

.

I don't think that you can use static fields.

But you can use using something like :

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let _hidden = ref 0 //to hide in the signature so that it is not accessible from uotside the module

type my_class () =
  static member run() = 
    incr _hidden 
    !hidden

or in a function :

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let increment =
  let _hidden = ref 0
  fun step -> 
    _hidden := !_hidden + step 
    !_hidden

(an example with collections can be found at :
[link:blogs.msdn.com] )

Hope this helps

By on 9/13/2007 12:06 AM ()

Yes, you currently use a mutable or "ref" in a module.

We agree this is a bit of a pain since it can need to a needless extra module and also recursion problems (sometimes you have to give the field a type involving "obj" to avoid the latter, adding box and unbox). As a result static declarations in classes are planned for inclusion.

Kind regards

don

By on 9/13/2007 2:52 AM ()

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