cout << oct << -12 << endl; ?

This is a discussion on cout << oct << -12 << endl; ? within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> #include <iomanip> using namespace std; int main() { int num; while (true) { cout << "N: "; ...

  1. #1
    Banned
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    Nov 2007
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    cout << oct << -12 << endl; ?

    Code:
    #include <iostream>
    #include <iomanip>
    
    using namespace std;
    
    int main()
    {
        int num;
        while (true)
        {
            cout << "N: ";
            cin >> num;
            if (! num) break;
            cout << hex << num << " " << dec << num << " " << oct << num << endl;
        }
        
        return 0;
    }
    output:
    N: 12
    c 12 14
    N: -12
    fffffff4 -12 37777777764
    N:0

    Question: Why negative numbers get strange values in hex and oct?
    Actually I feel the hex value is natural, since that's how a negative number is internally. But why oct output is garbage?

  2. #2
    Kernel hacker
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    Location
    Farncombe, Surrey, England
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    15,677
    Because hex and octal are defaulting to unsigned int instead of signed, it would appear.

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    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
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