#include <iostream>
#include <string>
#include <process.h>
using namespace std;
double eval(double a, double b, char op)
{
double r;
switch(op)
{
case '+':
r = a + b;
break;
case '-':
r = a - b;
break;
case '*':
r = a * b;
break;
case '/':
if (b == 0)
{
cout << "除数不能为 0...." << endl;
return 0;
}
r = a / b;
break;
}
return r;
}
void calc()
{
double a = 0.0, b = 0.0;
char op;
cout << "请输入计算式" << endl;
cin >> a >> op >> b;
cout << eval(a, b, op) << endl;
}