Example of a coroutine/generator in C

iterate.c

#include <stdio.h>
#include "coroutine.h"

typedef struct
{
    int max_x;
    int max_y;
    int state;
    int x;
    int y;
} iter;

int
iterate(iter *i)
{
    start(i->state);
    for(i->x = 0; i->x < i->max_x; i->x++)
    {
        for(i->y = 0; i->y < i->max_y; i->y++)
        {
            yield(i->state, 1);
        }
    }
    finish;

    return 0;
}

int
main(void)
{
    iter i = {2, 2};
    while(iterate(&i))
    {
        printf("%d %d\n", i.x, i.y);
    }

    return 0;
}

coroutine.h defined in https://gist.github.com/laindir/6369535