Receiving integers, but also want to test for char.

Question

Say I am looking to receive a series of numeric values and read them into an int, but I also want to test if the user hit key 'x'.

I am sure I am missing something obvious, and have tried a few things but seem to be stuck.

This is what I have so far...
cout << endl << "Enter key (or 'x' to exit): ";
cin >> key;
if (key == 'x') { cout << "exiting";}
// continue on...

Answer 1

You need to read into a string and then convert that to an integer. In outline:

#include <string>
#include <sstream>
#include <iostream>
using namespace std;

int main() {
  string s;
  cout << endl << "Enter key (or 'x' to exit): ";
  getline( cin, s );
  if ( s == "x" ) {
    // do exit stuff
  }
  else {
     istringstream is( s );
     int n;
     if ( ! is >> n ) {
        // report not an integer
     }
     else {
        // do something with n
     }
  }
}

Answer 2

It depends on how key is declared. If key is an int, you can only test for numbers, of course.

How about the following outline of an algorithm:

int n = 0
bool xentered = false
while (not xentered and there is one more character before EOF)
  if that character is 'x' then xentered = true
  else if it is a digit
     n = 10*n + numeric value of the digit
  else
    error

I leave the task to translate that to the programming language of your choice. :)