I don't quite get foreach ref

[Steven Schveighoffer]

On Sun, 08 Aug 2010 06:01:20 -0400, Tomek Sowiński <just at ask.me> wrote:

> struct DumbRange {
>     int front() { return 5; }             // rvalue
>     void popFront() { --counter; }
>     bool empty() { return counter > 0; }
>     uint counter = 10;
> }
>
> void clear(ref int a) { a = 0; }
>
> void main() {
>     auto r = DumbRange();
>
>     // Doesn't compile (and good): r.front() is not an lvalue
>     clear(r.front);
>
>     // Confusingly has no effect. Yet, compiles -- should it?
>     foreach(ref a; r) a = 0;
> }
>
> I don't know what to make of it, the D page says nothing on foreach ref  
> on rvalues.

Historically, when using opApply to implement foreach, opApply's delegate  
must take all ref arguments.  This is a source of pain because if you  
don't want to ref your data, you had to make temporary copies.

I don't know why ranges have propagated this silliness.

You should file a bug.  Also vote for mine:  
http://d.puremagic.com/issues/show_bug.cgi?id=2443

-Steve