C语言 14 模拟计算器 版本更迭

//模拟计算器：
void menu()
{
  printf("*****************************************\n");
  printf("************  1.add    2.sub  ***********\n");
  printf("************  3.mul    4.div  ***********\n");
  printf("************      0.exit      ***********\n");
  printf("*****************************************\n");
}
int Add(int x, int y)
{
  return x + y;
}
int Sub(int x, int y)
{
  return x - y;
}
int Mul(int x, int y)
{
  return x * y;
}
int Div(int x, int y)
{
  return x / y;
}
int main()
{
  int input = 0;
  int x = 0;
  int y = 0;
  int ret = 0;
  do
  {
    menu();
    printf("请选择:>\n");
    scanf("%d", &input);
    switch (input)
    {
    case 1:
      printf("请输入两个操作数\n");
      scanf("%d %d",&x, &y);
      ret = Add(x, y);
      printf("ret = %d\n", ret);
      break;
    case 2:
      printf("请输入两个操作数\n");
      scanf("%d %d", &x, &y);
      ret = Sub(x, y);
      printf("ret = %d\n", ret);
      break;
    case 3:
      printf("请输入两个操作数\n");
      scanf("%d %d", &x, &y);
      ret = Mul(x, y);
      printf("ret = %d\n", ret);
      break;
    case 4:
      printf("请输入两个操作数\n");
      scanf("%d %d", &x, &y);
      ret = Div(x, y);
      printf("ret = %d\n", ret);
      break;
    case 0:
      printf("退出计算器\n");
      break;
    default:
      break;
    }
  } while (input); 
  return 0;
}
​

//模拟计算器简单改良版
void menu()
{
  printf("*****************************************\n");
  printf("************  1.add    2.sub  ***********\n");
  printf("************  3.mul    4.div  ***********\n");
  printf("************      0.exit      ***********\n");
  printf("*****************************************\n");
}
int Add(int x, int y)
{
  return x + y;
}
int Sub(int x, int y)
{
  return x - y;
}
int Mul(int x, int y)
{
  return x * y;
}
int Div(int x, int y)
{
  return x / y;
}
int main()
{
  int input = 0;
  int x = 0;
  int y = 0;
  int ret = 0;
  do
  {
    menu();
    printf("请选择:>\n");
    scanf("%d", &input);
    printf("请输入两个操作数\n");
    scanf("%d %d", &x, &y);
    switch (input)
    {
    case 1:
      ret = Add(x, y);
      printf("ret = %d\n", ret);
      break;
    case 2:
      ret = Sub(x, y);
      printf("ret = %d\n", ret);
      break;
    case 3:
      ret = Mul(x, y);
      printf("ret = %d\n", ret);
      break;
    case 4:
      ret = Div(x, y);
      printf("ret = %d\n", ret);
      break;
    case 0:
      printf("退出计算器\n");
      break;
    default:
      break;
    }
  } while (input);
  return 0;
}

//函数指针数组的应用
//case语句越来越长的增强：
void menu()
{
  printf("*****************************************\n");
  printf("************  1.add    2.sub  ***********\n");
  printf("************  3.mul    4.div  ***********\n");
  printf("************      0.exit      ***********\n");
  printf("*****************************************\n");
}
int Add(int x, int y)
{
  return x + y;
}
int Sub(int x, int y)
{
  return x - y;
}
int Mul(int x, int y)
{
  return x * y;
}
int Div(int x, int y)
{
  return x / y;
}
int main()
{
  int input = 0;
  int x = 0;
  int y = 0;
  int ret = 0;
  do
  {
    menu();
    printf("请选择:>\n");
    scanf("%d", &input);
    //创建一个函数指针数组
      //函数指针数组  转移表
    int (*pfArr[])(int, int) = { NULL,Add,Sub,Mul,Div };
    //                            0    1   2   3   4
    if (0 == input)
    {
      printf("退出计算器\n");
    }
    else if (input >= 1 && input <= 4)
    {
      printf("请输入两个操作数\n");
      scanf("%d %d", &x, &y);
      ret = pfArr[input](x, y);
      printf("ret=%d\n", ret);
    }
    else
    {
      printf("选择错误，重新选择!\n");
    }
  } while (input);
  return 0;
}

void menu()
{
  printf("*****************************************\n");
  printf("************  1.add    2.sub  ***********\n");
  printf("************  3.mul    4.div  ***********\n");
  printf("************      0.exit      ***********\n");
  printf("*****************************************\n");
}
int Add(int x, int y)
{
  return x + y;
}
int Sub(int x, int y)
{
  return x - y;
}
int Mul(int x, int y)
{
  return x * y;
}
int Div(int x, int y)
{
  return x / y;
}
void calc(int (*pf)(int, int))//函数指针
{
  int x = 0;
  int y = 0;
  int ret = 0;
  printf("请输入两个操作数\n");//没有直接调用函数，将地址传给这个函数，在这个函数内部调用
  scanf("%d %d", &x, &y);//这里的加减乘除就是回调函数
  ret = pf(x, y);//调用函数并返回
  printf("ret = %d\n", ret);
}
int main()
{
  int input = 0;
  do
  {
    menu();
    printf("请选择:>\n");
    scanf("%d", &input);
    switch (input)
    {
    case 1:
      calc(*Add);
      break;
    case 2:
      calc(*Sub);
      break;
    case 3:
      calc(*Mul);
      break;
    case 4:
      calc(*Div);
      break;
    case 0:
      printf("退出计算器\n");
      break;
    default:
      break;
    }
  } while (input);
  return 0;
}