Automatic opApply iteration counter

[Steven Schveighoffer]

bearophile Wrote:

> I have not written this as enhancement request on Bugzilla because while I have a clear (small) problem, I think my possible solution is bad (see at the bottom).
> 
[snip]
> To allow both the foreach version with and without index I have to duplicate the body of the opApply, but this code duplication is bad:

No.  This is how I do it in dcollections (for optional keys in map containers):


> import std.stdio: writeln;
> struct Xfibonacci {
>     long max;
>     this(long inmax) { max = inmax; }
>     int opApply(int delegate(ref long) dg) {
           int _dg(ref int i, ref long l) { return dg(l); }
           return opApply(&_dg);
>     }
>     int opApply(int delegate(ref int, ref long) dg) {
>         int result, index;
>         long a=0, b=1;
>         while (a < max) {
>             result = dg(index, b);
>             if (result) break;
>             index++;
>             a += b;
>             result = dg(index, a);
>             if (result) break;
>             b += a;
>             index++;
>         }
>         return result;
>     }
> }

Don't forget, opApply is just a function, you can use it as such :)