Operators overloading in D2

[Steven Schveighoffer]

On Mon, 17 May 2010 16:38:49 -0400, Larry Luther <larry.luther at dolby.com>  
wrote:

> Hi, Dan used the following method for his vector class:
>
>   void opOpAssign (string op:"+=")(ref Vector3 other) {...}
>
> Why the "ref"?  As I understand it, objects of class vector
> would already be passed as references.
>
>   Larry

Yes, ref is redundant in this case.  However, you can ref a class  
reference, meaning you can change the passed-in class reference.

An example:

class C
{
   int x;
}

void foo(ref C xyz)
{
    xyz.x = 5
    xyz = new C;
    xyz.x = 6;
}

void bar(C xyz)
{
    xyz.x = 7;
    xyz = new C;
    xyz.x = 8;
}

void baz()
{
    C c = new C;
    c.x = 1;
    C c2 = c;
    foo(c);
    // foo changed the x member of the object c and c2 pointed to, and then
    // actually changed the object c points to.
    assert(c.x == 6 && c2.x == 5 && c !is c2);

    c2 = c;
    c.x = 1;
    bar(c);

    // bar changed the x member of the object c and c2 pointed to, and then
    // created a local C which did not affect the class reference passed in.
    assert(c.x == 7 && c2.x == 7 && c is c2);
}

-Steve