Generators

A minimal generator facility: range_gen produces a lazy sequence and next advances it, mirroring Python's range iterator.

#include "abscom/abs.h"

Function	Description
var range_gen(long start, long stop, long step)	A generator yielding start, start+step, ... while below stop (above for negative step).
var next(var gen)	The next value, or None once the generator is exhausted.

range_gen returns an ABS_GENERATOR object. A step of 0 returns an error; negative steps count down. Calling next on a non-generator returns an error.

var g = range_gen(0, 5, 2);
var n;
while ((n = next(g)) != NULL && !is_none(n)) {
    print(n);        /* 0  2  4 */
}

Generators pair naturally with the foreach macro:

var item;
foreach (item, range_gen(10, 0, -3)) {
    print(item);     /* 10  7  4  1 */
}

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