std::cin doesn't throw an exception on bad input

Question

I am just trying to write a simple program that reads from cin, then validates that the input is an integer. If it does, I will break out of my while loop. If not, I will as

Answer 1

Don't use using namespace std; Instead import what you need.

It's better to do input a line at a time. This makes behavior much more intuitive if you have multiple words on one line, or if you press enter before typing anything.

#include 
#include 
#include 

using std::cerr;
using std::cin;
using std::cout;
using std::endl;
using std::flush;
using std::getline;
using std::istringstream;
using std::string;

int main() {
    int input;
    while (true)
    {
        cout << "Please enter an integral value: " << flush;
        string line;
        if (!getline(cin, line)) {
            cerr << "input failed" << endl;
            return 1;
        }
        istringstream line_stream(line);
        char extra;
        if (line_stream >> input && !(line_stream >> extra))
            break;
    }
    cout << input << endl;
    return 0;
}