#include <stdio.h>
 
#define DECLARE() int state = 0
 
#define BEGIN switch (state) { \
                      case 0:
 
#define YIELD(val) do { \
                        state = __LINE__;   \
                        return val;         \
                      case __LINE__:        \
                        ;                   \
                      } while (0)
 
#define END }
 
int next()
{
    static DECLARE();
    static int i=1;
    BEGIN;
        YIELD(++i);
        YIELD(++i);
    END;
    return 0;
}
int main()
{
    int num;
    while (num = next()) {
        printf("%d\n", num);
    }
    printf("done\n");
    return 0;
}

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