Check for global operator<< for GCC 4.7.2, lang 3.1, VC2010, VC8, VC6

InsertionOpDetector.cpp

// http://stackoverflow.com/a/5771273/437272

#include <iosfwd>

namespace detail {
  typedef char no;
  typedef char yes[2];

  struct any_t {
    template<typename T> any_t( T const& );
  };

  no operator<<( std::ostream const&, any_t const& );

  yes& test( std::ostream& );
  no test( no );

  // VC6 requires name to differ from parent class
  template<typename T>
  struct has_insertion_operator_impl {
    static std::ostream &s;
    static T const &t;

    enum { value = sizeof( test(s << t) ) == sizeof( yes ) };
  };
}

template<typename T>
struct has_insertion_operator : detail::has_insertion_operator_impl<T> {};

// --

#include <iostream>

struct S{};
struct X{};
std::ostream & operator << (std::ostream & os, S const & ) { return os;}

int main(void)
{
    std::cout << has_insertion_operator<int>::value << std::endl;
    std::cout << has_insertion_operator< S >::value << std::endl;
    std::cout << has_insertion_operator< X >::value << std::endl;
}

// cl -nologo -EHsc InsertionOpDetector-vc6.cpp && InsertionOpDetector-vc6
// g++ -o InsertionOpDetector-vc6.exe InsertionOpDetector-vc6.cpp && InsertionOpDetector-vc6
// C:\Programs\mingw-clang-3.1\bin\clang++ -o InsertionOpDetector-vc6.exe InsertionOpDetector-vc6.cpp && InsertionOpDetector-vc6

// works with
// GCC 4.7.2
// clang 3.1
// VS2010 (VC10), VS2005 (VC8), VS6 (VC6)