C语言中函数指针的三种使用方法总结

#include <stdio.h>
int sum(int x, int y){
  return x + y;
}
int reduce(int x, int y){
  return x - y;
}
int multiply(int x, int y){
  return x * y;
}
float divide(int x, int y){
  if(y ==0)
    return 0;
  else
    return x *1.0f/ y;
}

struct Student{
  int age;
  float weight;
  char *name;
  void(*studentP());
}

int main(int argc, const char * argv[])
{

  // 1.定义函数指针
  int (*p)(int x, int y);
  // 2.初始化
  p = sum;
  // 3.赋值
  int s = p(3,2);
  // 4.打印
  printf("%d\n",s);//=5;

  //--------------
  printf("请输入数字1,2,3,4\n");
  int num;
  scanf("%d",&num);

  switch (num) {
    case 1:
      p = sum;
      break;
    case 2:
      p = reduce;
      break;
    case 3:
      p = multiply;
      break;
    case 4:
      p = divide;
      break;

  }
  int result = p(22,2);

  printf("%d\n",result);

  //结构体：
  struct Student stu = (22,88,"tom",studp);
  printf("结构体长度=%d",sizeof(stu));
  //1.
  stu.studp;
  //2.
  struct stu* stp = &stu;
  (*stp).studp;
  //3.
  stp -> studp;

  return 0;
}