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