(持续更新中!!~)13、原来可以这样理解C语言_理解指针(6/6)转移表

目录

 6. 转移表

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 6. 转移表

        函数指针数组的⽤途：转移表

        举例：计算器的⼀般实现：

#include <stdio.h>

int add(int a, int b)
{
 return a + b;
}

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

int mul(int a, int b)
{
 return a * b;
}

int div(int a, int b)
{
 return a / b;
}

int main()
{
 int x, y;
 int input = 1;
 int ret = 0;
 do

 {
 printf("*************************\n");
 printf(" 1:add 2:sub \n");
printf(" 3:mul 4:div \n");
 printf(" 0:exit \n");
 printf("*************************\n");
 printf("请选择：");
 scanf("%d", &input);
 switch (input)
 {
 case 1:
 printf("输⼊操作数：");
 scanf("%d %d", &x, &y);
 ret = add(x, y);
 printf("ret = %d\n", ret);
 break;
 case 2:
 printf("输⼊操作数：");
 scanf("%d %d", &x, &y);
 ret = sub(x, y);
 printf("ret = %d\n", ret);
 break;
 case 3:
 printf("输⼊操作数：");
 scanf("%d %d", &x, &y);
 ret = mul(x, y);
 printf("ret = %d\n", ret);
 break;
 case 4:
 printf("输⼊操作数：");
 scanf("%d %d", &x, &y);
 ret = div(x, y);
 printf("ret = %d\n", ret);
 break;
 case 0:
 printf("退出程序\n");
 break;
 default:
 printf("选择错误\n");
 break;
 }
 } while (input);
 return 0;
}

        使⽤函数指针数组的实现：

#include <stdio.h>

int add(int a, int b)
{
 return a + b;
}

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

int mul(int a, int b)
{
 return a*b;
}

int div(int a, int b)
{
 return a / b;
}

int main()
{
 int x, y;
 int input = 1;
 int ret = 0;
 int(*p[5])(int x, int y) = { 0, add, sub, mul, div }; //转移表 
 do

 {
 printf("*************************\n");
 printf(" 1:add 2:sub \n");
 printf(" 3:mul 4:div \n");
 printf(" 0:exit \n");
 printf("*************************\n");
 printf( "请选择：" );
 scanf("%d", &input);
 if ((input <= 4 && input >= 1))
 {
 printf( "输⼊操作数：" );
 scanf( "%d %d", &x, &y);
 ret = (*p[input])(x, y);
 printf( "ret = %d\n", ret);
 }
 else if(input == 0)
 {
 printf("退出计算器\n");
 }
 else

 {
 printf( "输⼊有误\n" ); 
 }
}while (input);
 return 0;
}