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Define multiple types
f#

Hello, group

I am newbie to F#. I have a C# type like:

class A { public int Type };

different types can be differed from Type member in the class. How can i define multiple types in F# by using the Type variable in A class? Something like:

type Type0 = A where A.Type==0

type Type1 = A where A.Type==1

Thanks for help.

.

Not quite sure what you're asking, but if you're not familiar with discriminated unions in F# (or algebraic data types in general), check them out.

[link:lorgonblog.spaces.live.com]

By on 3/8/2009 11:32 PM ()

Thanks, guys. I believe I got what I want. Discriminated unions is the problem. :)

By on 3/9/2009 9:37 AM ()

You can use active patterns as in :

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type Foo(v:int) =
  member x.X = v

let (|FooA|FooB|) (x:Foo) = 
  match x.X with 
  | 0 -> FooA "aha" 
  | 1 -> FooB 1234 
  | _ -> invalid_arg "unexpected value" ;;

See the attached pdf at [link:blogs.msdn.com] for more information

By on 3/8/2009 11:15 PM ()

The value of a member of an object is not a part of that object's type. If you want an instance of A with the member Type set to 0, then give A a constructor which allows Type to be initialized, or if it's a public property, you can just initialize the property within the construction expression: 

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new A(Type = 0)

.

By on 3/8/2009 11:11 PM ()

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