C++ switch statement Models calculator

#include <iostream>
using namespace std;
int main()//from   w ww. j a  v a  2  s. c om
{
   double n1, n2, ans;
   char oper, ch;
   do {
      cout << "\nEnter first number, operator, second number: ";
      cin >> n1 >> oper >> n2;
      switch(oper)
      {
         case '+':  ans = n1 + n2;  break;
         case '-':  ans = n1 - n2;  break;
         case '*':  ans = n1 * n2;  break;
         case '/':  ans = n1 / n2;  break;
         default:   ans = 0;
      }
      cout << "Answer = " << ans;
      cout << "\nDo another (Enter 'y' or 'n')? ";
      cin >> ch;
   } while( ch != 'n' );
   return 0;
}