Question

I did the following method as in http://www.parashift.com/c++-faq-lite/input-output.html to validate, but it does not work:

if (!(cin >> hex >>address1))
    {
        cout << "Invalid input.";               
        std::cin.clear();
        std::cin.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
    }   

It keeps carrying the remaining input to the next input, thus making the next input cannot be typed in by user, even the std::cin is cleared and ignored.

Answer 1

I guess I’d do something like this:

std::getline(cin, your_string);

if (your_string.find_first_not_of("0123456789abcdefABCDEF") != std::string::npos)
    error("Non-hexadecimal input");
else {
    std::istringstream is(your_string);
    is >> std::hex >> address1;
}

There are a lot of variations, but the three steps I’d follow would be:

1. read the whole line,
2. validate it
3. convert if good.