Static operator overloads are possible why?

[Bill Baxter]

Just a couple of quick comments about your post:
1) It looks like you're reinventing std.signals.
2) The usual operator for adding another handler onto a list is ~= 
(opCatAssign) not +=.

--bb



Giles Bathgate wrote:
> Dear Mr Bright;
> 
> I have been playing with D and have come across what I believe to be a bug/feature idea.
> 
> It all started when I tried to emulate C# Style events, (Dont worry this is not a request to add events to the language) 
> I was really impressed by the power of the D language and found that I could make what microsoft call Multicast delegates
> So in my opinion there is no need to add them.
> 
> However,
> 
> the way I add handlers to the multicast delegate is using the following syntax:
> 
> this.add_Paint = new PaintEventHandler(&Form1_Paint);
> 
> as opposed to microsofts syntax of
> 
> this.Paint += new PaintEventHandler(Form1_Paint);
> 
> So I started investigating using opAddAssign overloads.
> 
> Ok Introduction over Let me get to the point.
> 
> Consider the following code:
> 
> 
> public class Test
> {
> 	public char[] Name;
> 
> 	public Test opAddAssign(Test value)
> 	{
> 		writefln(value.Name);
> 		//TODO...
> 	}
> } 
> 
> int Main()
> {
> 	Test t;
> 	Test b = new Test();
> 
> 	t += b; //Runtime exception because t is null
> 
> }
> 
> This code obviously has a runtime exception because t was not assigned and the translation of the code t += b; becomes 
> t.opAddAssign(b); 'ok I thought', I shall make the operator overload static...'er no wait can I do that?'
> 
> half expecting a compile error I tried anyway
> 
> 
> public class Test
> {
> 	public char[] Name;
> 
> 	public static Test opAddAssign(Test value)
> 	{
> 		writefln(value.Name);
> 		//TODO...
> 	}
> } 
> 
> int Main()
> {
> 	Test t;
> 	Test b = new Test();
> 	b.Name = "foo"
> 
> 	t += b; // Translates to:   Test.opAddAssign(b);
> 
> }
> 
> output: foo
> 
> The code compiles, and runs, and opAddAssign actually gets called, 
> 
> but wait surely t += b; translates to Test.opAddAssign(b);    
> 
> So how is that in anyway usefull? we have no reference to t, within our operator overload call. 
> (In the first example the reference to t could have been referenced by this)
> 
> So my question; 'should static operator overloads even be allowed?'
> and if they were to be allowed should they not have two arguments?
> 
> thus:
> 
> static Test opAddAssign(Test t, Test value){...}
> 
> 
> then 
> 
> t += b;
> 
> becomes
> 
> Test.opAddAssign(t,b);
> 
> Static operator overloads would be useful to me for this one particular application.
> Whats you view?
> 
> Regards
> 
> Mr _Bathgate;