【C语言】 模拟计算器

#include <stdio.h>
#include <stdlib.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)
{
if (b == 0)
{
printf("除数位0\n");
}
return a / b;
}

void menu()
{
printf("*************************\n");
printf("**** 1.add   2.sub   ****\n");
printf("**** 3.mul   4.div   ****\n");
printf("******** 0.exit *********\n");
printf("*************************\n");
}

int main()
{
int input = 1;
int num1 = 0;
int num2 = 0;
int ret = 0;
while (input)
{
menu();
printf("请选择>:");
scanf("%d", &input);
printf("请输入两个整数操作数>:");
scanf("%d%d", &num1, &num2);
switch (input)
{
case 1:
ret = _add(num1, num2);
break;
case 2:
ret = _sub(num1, num2);
break;
case 3:
ret = _mul(num1, num2);
break;
case 4:
ret = _div(num1, num2);
break;
case 0:
exit(EXIT_FAILURE);
break;
default:
printf("选择错误,请重新选择.\n");
break;
}
printf("ret = %d\n", ret);
}
return 0;
}

此外，也可以用枚举结构（enum）实现：

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

enum OP
{
EXIT,
ADD,
SUB,
MUL,
DIV
};
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)
{
if (b == 0)
{
printf("除数位0\n");
}
return a / b;
}

void menu()
{
printf("*************************\n");
printf("**** 1.add   2.sub   ****\n");
printf("**** 3.mul   4.div   ****\n");
printf("******** 0.exit *********\n");
printf("*************************\n");
}

int(*pfun[5])(int, int) = {0, _add, _sub, _mul, _div};

int main()
{
int input = 1;
int num1 = 0;
int num2 = 0;
int ret = 0;
while (input)
{
menu();
printf("请选择>:");
scanf("%d", &input);
printf("请输入两个整数操作数>:");
scanf("%d%d", &num1, &num2);
if (input >= 1 && input <= 4)
{
ret = pfun[input](num1, num2);
}
else if (input == 0)
{
exit(EXIT_FAILURE);
}
else
{
printf("选择错误\n");
}
printf("ret = %d\n", ret);
}
return 0;
}