C 中的 Python 风格迭代器

Question

python 中的“yield”语句允许从过程中进行简单的迭代，这也意味着不需要预先计算序列并将其存储在“任意”大小的数组中。

是否有类似的方法从 C 程序迭代(使用 yield)？

Answer 1

下面是 self 回答的社区维基副本，可以将其选为“the”答案。请直接对实际的 self 回答投赞成票/反对票

这是我找到的方法:

    /* Example calculates the sum of the prime factors of the first 32 Fibonacci numbers */
#include <stdio.h>

typedef enum{false=0, true=1}bool;

/* the following line is the only time I have ever required "auto" */
#define FOR(i,iterator) auto bool lambda(i); yield_init = (void *)&lambda; iterator; bool lambda(i)
#define DO {
#define     YIELD(x) if(!yield(x))return
#define     BREAK return false
#define     CONTINUE return true
#define OD CONTINUE; }
/* Warning: _Most_ FOR(,){ } loops _must_ have a CONTINUE as the last statement. 
 *  *   Otherwise the lambda will return random value from stack, and may terminate early */

typedef void iterator; /* hint at procedure purpose */
static volatile void *yield_init;
#define YIELDS(type) bool (*yield)(type) = yield_init

iterator fibonacci(int n){
   YIELDS(int);
   int i;
   int pair[2] = {0,1};
   YIELD(0); YIELD(1);
   for(i=2; i<n; i++){
      pair[i%2] = pair[0] + pair[1];
      YIELD(pair[i%2]);
   }
}

iterator factors(int n){
  YIELDS(int); 
  int i;
  for(i=2; i*i<=n; i++){
    while(n%i == 0 ){
      YIELD(i);
      n/=i;
    }
  }
  YIELD(n);
}

main(){
    FOR(int i, fibonacci(32)){
        printf("%d:", i);
        int sum = 0;
        FOR(int factor, factors(i)){
            sum += factor;
            printf(" %d",factor);
            CONTINUE;
        }
        printf(" - sum of factors: %d\n", sum);
        CONTINUE;
    }
}

灵感来自 http://rosettacode.org/wiki/Prime_decomposition#ALGOL_68 - 但它在 C 中读起来更好