Thread: Int, Char mix up

cin goes into an error state if that happens, which means it will ignore all further read requests. You can test this state with the fail() or good() methods, or just direct bool conversion:

Code:

if(cin) {
  // cin is fine
}
if(!cin) {
  // cin is not fine, either in error state or at end of file
}

You can call clear() to reset cin, but you also need to call ignore() to get rid of the invalid characters in the input buffer.

P.S: What's a "fourm rebel"?

It is easy to use a while loop to check for the int and prompt the user to try again if it is not a vali integer.

Code:

int value = 0;
// Prompt for input
while (!(std::cin >> value))
{
  std::cin.clear();
  std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
  // Tell the user they typed in bad input here and prompt again.
}

This is simple and works in most every case. One case where it might not work is if you want it to error out when the user types extra characters within or after the number (e.g. 1234abc or 123r5). To test for that, simply change the while loop to:

Code:

int value = 0;
// Prompt for input
while (!(std::cin >> value) || std::cin.get() != '\n')
{
  std::cin.clear();
  std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
  // Tell the user they typed in bad input here and prompt again.
}

Note that you have to #include <limits> to use numeric_limits. You can also just use a large number there.

Code:

while (!(std::cin >> value) && std::cin.get() != '\n')

I believe you must use || instead of && here.