Turn struct with opApply into ranages

rangeapply.d

struct applyRange(T, ElemType) {
	import core.thread;
	private {
		class rangeFiber : Fiber {
			ElemType *tmp = null;
			T r;
			this(T r) {
				this.r = r;
				super(&work);
			}
			int dg(ref ElemType x) {
				tmp = &x;
				f.yield();
				return 0;
			}
			void work() {
				r.opApply(&dg);
				tmp = null;
			}
		}
		rangeFiber f;
	}
	this(T r) {
		f = new rangeFiber(r);
		f.call();
	}
	ref ElemType front() {
		return *f.tmp;
	}
	void popFront() {
		f.call();
	}
	bool empty() {
		return f.tmp is null;
	}
}
struct Iter {
	int opApply(int delegate(ref int x) dg) {
		foreach(i; 0..10)
			dg(i);
		return 0;
	}
}
void main() {
	import std.stdio;
	Iter i;
	auto x = applyRange!(Iter, int)(i);
	foreach(y; x)
		writeln(y);
}