四则运算1

#include<stdio.h>int main()

{

    double a,b;

    char c;

    printf("Enter an expression: a+(-,*,/)b\n");

    scanf("%lf%c%lf",&a,&c,&b);

    while(a<0||b<0)

    {

        printf("输入出错!");

        printf("Enter an expression: a+(-,*,/)b\n");

        scanf("%lf%c%lf",&a,&c,&b);

      }

 

    

    if(c=='+')

        printf("=%lf\n",a+b);

    else if(c=='-')

        printf("=%lf\n",a-b);

    else if(c='*')

        printf("=%lf\n",a*b);

    else if(c='/')

        printf("=%lf\n",a/b);

    else

        printf("error");

    return 0;

}