Indexed foreach on struct?

[Ali Çehreli]

On 01/23/2012 01:16 PM, H. S. Teoh wrote:
 > On Mon, Jan 23, 2012 at 03:32:07PM -0500, Matt Soucy wrote:
 >> So I was messing around with some code I've been writing recently,
 >> and I wanted to use a foreach on a struct as if it were an
 >> associative array. The problem is, I can't find any information on
 >> how to do that.
 > [...]
 >> I don't see any sort of opApply or similar to do this, and the
 >> foreach section of dlang.org doesn't help. Is there a way to do it,
 >> or do I need to do a workaround?
 > [...]
 >
 > You can use opApply.

And potentially more than one overload to match the foreach loop variables.

 > Sample test program:
 >
 > 	struct Test {
 > 		int opApply(int delegate(ref int) dg) {
 > 			auto ret = 0;
 > 			for (auto i=0; ret==0&&  i<5; i++) {
 > 				ret = dg(i);

Add:

     if (ret) {
        break;
     }

ret is non-zero if the foreach body contains a break statement.

 > 			}
 > 			return ret;
 > 		}
 > 	}
 >
 > 	import std.stdio;
 > 	void main() {
 > 		Test t;
 >
 > 		foreach (n; t) {
 > 			writeln(n);
 > 		}
 > 	}
 >
 > Program prints:
 >
 > 	0
 > 	1
 > 	2
 > 	3
 > 	4
 >
 > Hope that helps.
 >
 >
 > T
 >

Ali