Re: operator<< for std::map

From:

Carl Barron <cbarron413@adelphia.net>

Newsgroups:

comp.lang.c++.moderated

Date:

Tue, 30 Oct 2007 06:27:32 CST

Message-ID:

<291020071725402461%cbarron413@adelphia.net>

In article <1193658704.103141.69050@o38g2000hse.googlegroups.com>,
Daniel Kr?gler <daniel.kruegler@googlemail.com> wrote:

The following works due to ADL rules:

#include <utility>
#include <iostream>
#include <ostream>

namespace My {
  template <typename T>
  struct Writable{};

  template<typename T>
  std::ostream & operator<< (std::ostream & s,
   Writable<T> const &) {
      return s;
  }

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

int main() {
  std::pair<My::Writable<int>, double> pwi;
  std::cout << pwi;
}

  Does it really??
   std::pair<T1,T2> is in namespace std.
   std::basic_ostream<C,T> is in namespace std.
so search only namespace std.

  further all pwi will write if op << were found is
   comma, p->second. p->first writes nothing.

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