C 有“foreach"吗?循环构造? [英] Does C have a "foreach" loop construct?

问题描述

几乎所有语言都有 foreach 循环 或类似的东西.C有吗?你能发布一些示例代码吗?

Almost all languages have a foreach loop or something similar. Does C have one? Can you post some example code?

推荐答案

C 没有 foreach，但经常使用宏来模拟:

C doesn't have a foreach, but macros are frequently used to emulate that:

#define for_each_item(item, list) 
    for(T * item = list->head; item != NULL; item = item->next)

并且可以像这样使用

for_each_item(i, processes) {
    i->wakeup();
}

也可以对数组进行迭代:

Iteration over an array is also possible:

#define foreach(item, array) 
    for(int keep = 1, 
            count = 0,
            size = sizeof (array) / sizeof *(array); 
        keep && count != size; 
        keep = !keep, count++) 
      for(item = (array) + count; keep; keep = !keep)

并且可以像这样使用

int values[] = { 1, 2, 3 };
foreach(int *v, values) {
    printf("value: %d
", *v);
}

如果您也对 C++ 解决方案感兴趣，C++ 有一个原生的 for-each 语法，称为基于范围的 for"

In case you are also interested in C++ solutions, C++ has a native for-each syntax called "range based for"

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