A subthread of the "Impressed" thread revolved around D's lack of
a yield mechanism for iteration.
Nick Sabalausky mentioned his earlier attempt to create a library
based yield which unfortunately was too slow to compete with
explicit opApply/ranges [1].
I took a shot at it. It's fast. The resulting code is reasonably
pretty. But it doesn't provide a range interface, just opApply.
---
module yielder;
import core.thread;
/**
Examples:
---
import yielder;
import std.stdio;
auto y = new class Yielder!int {
final void yielding() {
yield(0);
yield(13);
yield(42);
}
};
foreach(x; y) {
writeln(x);
}
---
*/
class Yielder(E) {
abstract void yielding();
this() {
this.fiber = new Fiber(&yielding);
}
private {
Fiber fiber;
int result;
int delegate(ref E) callback;
}
final int opApply(int delegate(ref E) cb) {
callback = cb;
result = 0;
fiber.reset();
fiber.call();
return result;
}
final void yield(ref E value) {
result = callback(value);
if(result != 0) {
Fiber.yield();
}
}
final void yield(E value) {
yield(value);
}
}
---
[1]
https://semitwist.com/articles/article/view/combine-coroutines-and-input-ranges-for-dead-simple-d-iteration
