函数指针

形式：void (*fun_type) (int* a)

//例1，一个简单例子

void f(int *a){
  *a = 2333;
}


int main(){
  void (*pf)(int *a) = &f;


  int a = 5;
  f(&a);
  //下面两种调用方法结果一致，因为编译器使用函数名时总是会将其转换为函数指针，第二种的操作多余
  int b = 6;
  pf(&b);
  int c = 7;
  (*pf)(&c);


  int tt = 0;
  return 0;
}

//例2，函数类型定义后使用函数指针

typedef void (*fun_type) (int* a);


void fun(int *a){
  *a = 2333;
}


int main(){
  fun_type fun_instance = fun;


  //下面两种调用方法结果一致，因为编译器使用函数名时总是会将其转换为函数指针，第二种的操作多余
  int a = 5;
  fun(&a);


  int b = 6;
  (*fun)(&b);


  int tt = 0;
  return 0;
}

//例3，回调函数，查找链表节点

struct Node{
  int the_value;
  Node *node_next;
};


int compare_ints(void const *a, void const *b){
  if (*(int *)a == *(int *)b) //强制类型转换
    return 0;
  return 1;
}


Node *search_list(Node *node, void const *the_value, int (*compare)(void const *a, void const *b)){
  while (node != NULL){
    if (compare(&node->the_value, the_value) == 0)
      break;
    node = node->node_next;
  }
  return node;
}


int main(){
  Node *first = new Node;
  Node *second = new Node;
  Node *third = new Node;


  first->the_value = 1;
  first->node_next = second;
  second->the_value = 2;
  second->node_next = third;
  third->the_value = 3;
  third->node_next = NULL;


  int desired_value = 2;
  Node *desired_node = search_list(first, &desired_value, compare_ints);


  int tt = 0;
  return 0;
}