Question

I was wondering, how would I be able to compare a variable which is supposed to hold integer values, to times when it is passed a char value:
For example:

int i;
cin >> i;
if(i == integer)
          execute a command;
else (if i == char)
          do something else here;

Since x can’t hold a character value, would it just fail when someone tries to input a character value in i?

Answer 1

Get input into a string, then try to convert it to an integer (you have a myriad of options here, boost::lexical_cast, std::istringstream, std::stoi, etc…). If the conversion succeeds, you have an integer, if it fails, you don’t. Here’s an example using istringstream:

std::string input;
std::cin >> input;
std::istringstream iss(input);
int x;
if (iss >> x)
{
    // success
}
else
{
    // failure
}

If you don’t care what the input was in the case that it wasn’t an integer, you can just check for failure directly on input into an int:

int x;
if (cin >> x)
{
    // success
}
else
{
    // get cin out of the error state
    cin.clear();
}