例3-9

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

    printf("Type in an expression:");
    scanf("%lf%c%lf",&valuel,&op,&value2);
    switch(op){
    case'+':
        printf("=%.2f\n",valuel+value2);
        break;
    case'-':
        printf("=%.2f\n",valuel-value2);
        break;
    case'*':
        printf("=%.2f\n",valuel*value2);
        break;
    case'/':
        printf("=%.2f\n",valuel/value2);
        break;
    default:
        printf("Unknown operator\n");
        break;
    }
    return 0;
}