Infinite loop with cin when typing string while a number is expected

Question

In the following loop, if we type characters as the cin input instead of numbers which are expected, then it goes into infinite loop. Could anyone please explai

Answer 1

Attention

Please pay attention to the following solution. It is not complete yet to clear the error in your case. You will still get an infinite loop!

if (cin.fail())
{
     cout << "Please enter an integer";
     cin.clear();
}

Complete Solution

The reason is you need clear the failed state of stream, as well as discard unprocessed characters. Otherwise, the bad character is still there and you still get infinite loops. You can simply can std::cin.ignore() to achieve this. For example,

if (cin.fail())
{
         cout << "Please enter an integer";
         // clear error state
         cin.clear();
         // discard 'bad' character(s)
         cin.ignore(std::numeric_limits::max(), '\n');
}

Another Solution

You can also use getline and stringstream to achieve. Here is a brief example.

   string input;
   while (1)
   {
      getline(cin, input);
      stringstream(input) >> x;
      cout << x << endl;
   }