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I would like a setw to take two parameters and return the largest. Is this possible? How do I go about doing this? Not looking for code just some direction would be fine as I couldn't find a clear answer on-the-line.

Alexander
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  • You cannot overload it directly since it resides in namespace std (and adding custom overloads there is forbidden generally). I think it's possible to use some name lookup tricks to overload it in another namespace; but I don't quite see the advantage over Remy Lebeau's solution. – dyp Sep 08 '14 at 20:22

1 Answers1

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I don't think you can overload it, but you can certainly define your own type with a different name and then define << and >> operators for it. For example:

struct setw_largest
{
    int _value;
    setw_largest(int value1, int value2) : _value(std::max(value1, value2)) {}
};

template<class _Elem, class _Traits, class _Arg>
inline basic_istream<_Elem, _Traits>& operator>>(basic_istream<_Elem, _Traits>& _Istr, const setw_largest& _Manip)
{
    _Istr.width(_Manip._value);
    return _Istr;
}

template<class _Elem, class _Traits, class _Arg>
inline basic_ostream<_Elem, _Traits>& operator<<(basic_ostream<_Elem, _Traits>& _Ostr, const setw_largest& _Manip)
{
    _Ostr.width(_Manip._value);
    return _Ostr;
}


std::cin >> setw_largest(1, 2) >> ...;
std::cout << setw_largest(1, 2) << ...;
Remy Lebeau
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  • The STL consists of mostly header files and inline implementations, so you can simply look at the `setw()` implementation to see what it actually does. – Remy Lebeau Sep 08 '14 at 20:17
  • Underscore + capital letter = reserved identifier, [global.names]. This is intended in an StdLib implementation, but your own extensions shouldn't use them. – dyp Sep 08 '14 at 20:19
  • I will tackle this and give you feedback later. Thanks for the help. – Alexander Sep 08 '14 at 20:20