第三章3-5

#include<stdio.h>
int main(void)
{
 double value1,value2;
 char op;
 printf("Type in an expression:");
 scanf("%lf%c%lf",&value1,&op,&value2);

 if(op=='+')
  printf("=%.2f\n",value1+value2);
 else if(op=='-')
  printf("=%.2f\n",value1-value2);
 else if(op=='*')
  printf("=%.2f\n",value1*value2);
 else if(op=='/')
  printf("=%.2f\n",value1/value2);
 else
  printf("Unknown operator\n");

 return 0;
}