例3-9 四则运算

程序核心——switch循环语句

程序

#include<stdio.h>
int main()
{
    double value1,value2;
    char op;
    
    printf("Type in an expression:");
    scanf("%lf%c%lf",&value1,&op,&value2);
    switch(op)
    {
        case'+':printf("=%.2f",value1+value2);
                break;
        case'-':printf("=%.2f",value1-value2);
                break;
        case'*':printf("=%.2f",value1*value2);
                break;
        case'/':printf("=%.2f",value1/value2);
                break;
        default:printf("Unknown operator\n");
                break;
    }
    return 0;   
 } 

结果

Type in an expression:9.9+0.01
=9.91
--------------------------------
Process exited after 14.53 seconds with return value 0
请按任意键继续. . .

分析

重点：switch语句判断的是一个常量