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How to combine values from enumeration types in F#? I playing around with programming Windows Forms in F#, and I need to set control anchor styles. In C# or C++ it is done like this:

button1.Anchor = (AnchorStyles.Bottom | AnchorStyles.Right);

How to set this up in F#? Is there an operator defined to combine enum values?

Use Enum.combine, e.g. fom a different example exercising the .NET reflection library:

open System.Reflection
let callStaticMethod (ty:Type) name args =
  ty.InvokeMember(name,
    Enum.combine
     [ BindingFlags.InvokeMethod;
       BindingFlags.Static;
       BindingFlags.Public;
       BindingFlags.NonPublic ], null, null, args)

Cheers!

Don

What you need is "Enum.combine", see below link for more details:

http://research.microsoft.com/fsharp/manual/mllib/Microsoft.FSharp.MLLib.Enum.html

---

Robert Pickering
http://strangelights.com

And how about such code:

enum RuleTarget {

   Class = 0x0001, Delegate = 0x0002, Enum = 0x0004, Struct = 0x0008, 

   AllTypes = Class | Delegate | Enum | Struct,

}

?

Nemerle provides such ability in that way:

enum RuleTarget {

   | Class = 0x0001 | Delegate = 0x0002 | Enum = 0x0004 | Struct = 0x0008

   | AllTypes = Class %| Delegate %| Enum %| Struct

}

In F# enums can be create using the following syntax (note you must explicitly give the members a value to distinguish it from a union type):

[<System.Flags>]
type RuleTarget =
   | Class = 0x0001
   | Delegate = 0x0002
   | Enum = 0x0004
   | Struct = 0x0008

It's seems for the moment you can't reference enum members from there definition so you can't create a value "AllTypes" as a member (unless you work out its value). As a work around you can create a sperate value for all types:

let AllTypes = RuleTarget.Class ||| RuleTarget.Delegate ||| RuleTarget.Enum ||| RuleTarget.Struct

If this is really important to you send a feature request to the F# team, they've generally been quite good about small feature requests like this.

---

Robert Pickering
http://strangelights.com

Robert:

It's seems for the moment you can't reference enum members from there definition so you can't create a value "AllTypes" as a member (unless you work out its value). As a work around you can create a sperate value for all types:

let AllTypes = RuleTarget.Class ||| RuleTarget.Delegate ||| RuleTarget.Enum ||| RuleTarget.Struct

I think you'll agree that this is not the same. Actually, I don't see any value of AllTypes when it is not an enum's member.

Robert:

If this is really important to you send a feature request to the F# team, they've generally been quite good about small feature requests like this.

Important - is a wrong word for this. But, it is hell of a useful. I'll follow your advice and send a request ;)

ivan.eryshov:

Robert:

It's seems for the moment you can't reference enum members from there definition so you can't create a value "AllTypes" as a member (unless you work out its value). As a work around you can create a sperate value for all types:

let AllTypes = RuleTarget.Class ||| RuleTarget.Delegate ||| RuleTarget.Enum ||| RuleTarget.Struct

I think you'll agree that this is not the same. Actually, I don't see any value of AllTypes when it is not an enum's member.

I don't think I said it was the samething, I said it was a work arround and okay not a very good one ;). A better one is maybe to use F# binary litterals which make it a doodle to work flags:

[<System.Flags>]
type RuleTarget =
   | Class =    0b00000001
   | Delegate = 0b00000010
   | Enum =     0b00000100
   | Struct =   0b00001000
   | AllTypes = 0b00001111

 

---

Robert Pickering
http://strangelights.com

Robert:

A better one is maybe to use F# binary litterals which make it a doodle to work flags:

Yep! That what I'm doing. Thank you Robert!