A question about while loop

This is a discussion on A question about while loop within the C++ Programming forums, part of the General Programming Boards category; I thought I understood while and for loops quite well. However, recently I saw a program which had a while ...

  1. #1
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    A question about while loop

    I thought I understood while and for loops quite well. However, recently I saw a program which had a while loop which only contained:

    while (1)
    Can anyone please help me understand as to what condition is being tested here for being false of true? Thanks a lot.

    Arooj
    Last edited by Arooj; 02-16-2003 at 08:36 PM.

  2. #2
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    while(1) == while(true)

    I have barely used it, actually come to think of it, I don't think I ever have. But it could be used to show infinite loops.

    1 == true

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    Thanks Alpha, if it is an infinite loop, then how does the program terminate. Actually I had to write a program which keeps on taking input until it encounters 2 successive instances of zeros. This is how I wrote it. Tell me if this is the correc way.

    void ()
    {
    int num1, num2;
    cout << "Enter a digit: ";
    cin >> num1;
    cout << "Enter a digit: ";
    cin >> num2;
    while (1) {
    if (num1 == 0 && num2 == 0)
    break;
    cout << "Enter a digit: ";
    cin >> num1;
    if (num1 == 0 && num2 == 0)
    break;
    cout << "Enter a digit: ";
    cin >> num2;
    }

    }

    Can I instead write:
    while (num1 != 0 && num2 != 0)
    instead? I hope I made my problem clear. Thanks
    arj

  4. #4
    samurai warrior nextus's Avatar
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    then it will loop while num1 and num2 does not equal 0...so it will loop forever until num1 and num2 equal to zero...

  5. #5
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    Code:
        int num1,num2;
        cin >> num1 >> num2;
        while(num1!=0 && num2!=0) {
            num1 = num2;
            cin >> num2;
            if(!cin.good()) {
                cerr << "invalid input (expecting digit)" << endl;
                break; // or throw something
            }
    //      do something with num1 & num2
        }
    The previous code would fail on 5 0 0, assuming you wanted to stop on those consecutive zeros.

  6. #6
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    Thanks a lot. Actually program only checks 2 separate inputs to make sure both are not zeros. Thanks again.
    Arooj
    arj

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