C 函数指针

形式如下： 

int (*POINTER_NAME)(int a, int b)

int (*tester)(int a, int b) = sorted_order;
printf("TEST: %d is same as %d\n", tester(2, 3), sorted_order(2, 3));

 使用typedef可以给其它更复杂的类型起个新的名字。你需要记住的事情是，将typedef添加到相同的指针语法之前，然后你就可以将那个名字用作类型了。

#include <stdio.h>
#include <stdlib.h>


typedef int (*compare_cb)(int a, int b);

/**
 * A classic bubble sort function that uses the
 * compare_cb to do the sorting.
 */

int *bubble_sort(int *numbers, int count, compare_cb cmp)
{
    int temp = 0;
    int i = 0;
    int j = 0;
    int *target = malloc(count * sizeof(int));

    memcpy(target, numbers, count * sizeof(int));

    for(i = 0; i < count; i++) {
        for(j = 0; j < count - 1; j++) {
            if(cmp(target[j], target[j+1]) > 0) {
                temp = target[j+1];
                target[j+1] = target[j];
                target[j] = temp;
            }
        }
    }

    return target;
}

int sorted_order(int a, int b)
{
    return a - b;
}

int reverse_order(int a, int b)
{
    return b - a;
}


void test_sorting(int *numbers, int count, compare_cb cmp)
{
    int i = 0;
    int *sorted = bubble_sort(numbers, count, cmp);
    for(i = 0; i < count; i++) {
        printf("%d ", sorted[i]);
    }
    printf("\n");

    free(sorted);
}