Exiting a loop using a specific character.

[rythmicillusion]

I'm trying to write a little program that allows you to enter a couple integer values, print them to the screen, and continue indefinitely. To exit the program, I'd just like to be able to press a specific character ("x", for example) and hit enter.

Here is my code thus far...

***

int main()
{
int a=0;
int b=0;
cout<<"Please enter two integer values. To exit, press 'x', then press enter.\n";
while (a>=0, b>=0){
cin>>a>>b;
cout<<a<<"\t"<<b<<"\n";
if (a="x")
break;}
keep_window_open();}

***

Currently, I am allowed to enter one set of the two integer values and have them print. But after they print, the "Please enter a character to exit" message comes up. I am using Visual C++ 2008 Express on a Windows XP machine.

Thanks in advance!

[jsmith]

while( a>=0, b>=0 )

Does not do what you think, and besides, it isn't even what you want.

if( a="x" )

is triply wrong, first because it is an assignment not a comparison, second because it is assigning (or at least attempting to compare) an integer to a const char* (C string), and thirdly because an integer can never hold a non-integral value.

[joeriMJ]

a while loop is executed as long as its condition is true. So all you need to do is make sure the condition isn't met.
I don't know what the comma in your while condition means, but I usually use && or || depending on the situation. Could you tell me what it means?

2 things though, if(a="x")
the = operator is an assignment operator not a comparison operator. Never use it in a conditional statement like this.
If you were trying to compare a with "x", this would not be possible since a is declared as an integer and "x" is a const char *

[rythmicillusion]

Thanks you both for the input. I think I'm starting to see how to tweak the code.

I am unfamiliar with how to reassign "a" from an integer to a character in the loop.

joeriMJ: to answer your question, I believe that the comma in the while condition simply allows for more arguments to be added. I am *very* new to C++ and programming in general, so even talking about coding and calling everything by the proper label is still difficult.

[ragnamanga]

you can try this code:

include<iostream>
using namespace std;

int main()
{
char x, y;
while(1)
{
cout<<"enter 2 numbers";
cin>>x>>y>>;
cout<<x<<" "<<y;
if(x=='x'||y=='x')break;
}
}

i'm not sure though but i have tried it many times.
characters can also hold integers but with a very limited range.

[joeriMJ]

char can hold an integer, but only its integer value which you can find out using an ascii table.
For example the character '0' (zero) has ascii-code 43, the character '1' has ascii-code 44.
These may vary, since I don't know the table by heart :-)

This can be very usefull but keep in mind that the other way around (integers holding chars) is never possible.

Rythmicillusion: Do you know if seperating two conditions in a while using a comma will provide 'true' if both the conditions are met or if just one condition is met ?

Still I think it's always best to use && or ||
That's my experience from other programming languages and I can't seem to find that comma seperator anywhere in my C++ books.

[Duthomhas]

I always prefer to avoid "signal" characters. When the user is done, make it easy. Here's something I wrote a while ago to demonstrate the point.

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

int main() {
  vector<int> ints;
  string line;

  cout << "Please enter the elements of the array.\n"
       << "Press ENTER after each element.\n"
       << "Press ENTER on a blank line to stop."
       << endl;
  while (true) {
    getline( cin, line );
    if (line.empty()) break;

    stringstream ss( line );
    int value;
    ss >> value;

    ints.push_back( value );
    }

  cout << "Thank you. The array you entered is: ";
  for (unsigned i = 0; i < ints.size(); i++) cout << ints[ i ] << ' ';
  cout << endl;

  return 0;
  }

Again, this is a simple example. It could use a few improvements. But you can easily modify it to suit your needs.

Hope this helps.