Does C have a "foreach" loop construct?

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)

And can be used like

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

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)

And can be used like

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

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

Here is a full program example of a for-each macro in C99:

#include <stdio.h>typedef struct list_node list_node;struct list_node {    list_node *next;    void *data;};#define FOR_EACH(item, list) \    for (list_node *(item) = (list); (item); (item) = (item)->next)intmain(int argc, char *argv[]){    list_node list[] = {        { .next = &list[1], .data = "test 1" },        { .next = &list[2], .data = "test 2" },        { .next = NULL,     .data = "test 3" }    };    FOR_EACH(item, list)        puts((char *) item->data);    return 0;}

As you probably already know, there's no "foreach"-style loop in C.

Although there are already tons of great macros provided here to work around this, maybe you'll find this macro useful:

// "length" is the length of the array.   #define each(item, array, length) \(typeof(*(array)) *p = (array), (item) = *p; p < &((array)[length]); p++, (item) = *p)

...which can be used with for (as in for each (...)).

Advantages of this approach:

• item is declared and incremented within the for statement (just likein Python!).
• Seems to work on any 1-dimensional array
• All variables created in macro (p, item), aren't visible outside thescope of the loop (since they're declared in the for loop header).

Disadvantages:

• Doesn't work for multi-dimensional arrays
• Relies on typeof(), which is a GNU extension, not part of standard C
• Since it declares variables in the for loop header, it only works in C11 or later.

Just to save you some time, here's how you could test it:

typedef struct {    double x;    double y;} Point;int main(void) {    double some_nums[] = {4.2, 4.32, -9.9, 7.0};    for each (element, some_nums, 4)        printf("element = %lf\n", element);    int numbers[] = {4, 2, 99, -3, 54};    // Just demonstrating it can be used like a normal for loop    for each (number, numbers, 5) {         printf("number = %d\n", number);        if (number % 2 == 0)                printf("%d is even.\n", number);    }    char* dictionary[] = {"Hello", "World"};    for each (word, dictionary, 2)        printf("word = '%s'\n", word);    Point points[] = {{3.4, 4.2}, {9.9, 6.7}, {-9.8, 7.0}};    for each (point, points, 3)        printf("point = (%lf, %lf)\n", point.x, point.y);    // Neither p, element, number or word are visible outside the scope of    // their respective for loops. Try to see if these printfs work    // (they shouldn't):    // printf("*p = %s", *p);    // printf("word = %s", word);    return 0;}

Seems to work on gcc and clang by default; haven't tested other compilers.