例3-9

#include<stdio.h>
int main(void)
{
    double value1,value2;
    char op;

    printf("Type in an expression:");
    scanf("%lf%c%lf",&value1,&op,&value2);
    switch(op){
        case'+':
            printf("=%.2f\n",value1+value2);
            break;
        case'-':
            printf("=%.2f\n",value1-value2);
            break;
        case'*':
            printf("=%.2f\n",value1*value2);
            break;
        case'/':
            printf("=%.2f\n",value1+value2);
            break;
        default:
            printf("Unknown operator\n");
            break;
    }


    return 0;

}