例3-5

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

 if(op=='-')   printf("=%.2f\n",valuel+value2);  else if(op=='-')   printf("=%.2f\n",valuel-value2);  else if(op=='*')   printf("=%.2f\n",valuel*value2);  else if(op=='/')   printf("=%.2f\n",valuel/value2);  else   printf("Unknown operator\n");  return 0; }