Re: operator<< for std::map

From:
Alex Shulgin <alex.shulgin@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Sat, 20 Oct 2007 12:59:07 CST
Message-ID:
<1192888799.638211.298210@v29g2000prd.googlegroups.com>
On Oct 20, 1:28 am, mojmir <svobod...@gmail.com> wrote:

hello,

i am trying to dump whole map container to ostream like this:

template<typename T, typename U>
inline
std::ostream & operator<< (std::ostream & s, std::pair<T,U> const & p)
{
     s << "<" << p.first << "," << p.second << ">";
     return s;

}


Hm... I've just noticed that putting the above definition into
namespace std { ... } helps, so the problem might be somehow related
to ADL.

Tried to boil it down to the following, however "unsuccessfully"--it
still compiles:

namespace abc
{

     class stream
     {
     };

     template< typename T >
     void
     output(stream& s, T const& t)
     {
         s << t;
     }

     template< typename U, typename S >
     class pair
     {
     };

}

template< typename U, typename S >
void operator<<(abc::stream&, abc::pair< U, S > const&)
{
}

int
main()
{
     abc::stream stream;
     abc::pair< char, int > p;
     abc::output(stream, p);
}

--
Cheers,
Alex

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