#include<iostream> #include <stdlib.h> using namespace std; int main () { char c,flag; double a,b; while (1) { cin>>a>>c>>b; flag=1; switch(c) { case '+':a+=b;break; case '-':a-=b;break; case '*':a*=b;break; case '/':if(b==0){cout<<"出错!\n";flag=0;} else a/=b;break; default : cout<<"输入有误!\n";flag=0;return 0; } if(flag) cout<<"="<<a<<endl; } }