AC_DEFUN([AC_CXX_USING_OPERATOR],

  [AC_CACHE_CHECK(

      whether compiler supports using ::operator<<,

      ac_cv_cxx_using_operator,

      [AC_LANG_SAVE

       AC_LANG_CPLUSPLUS

       AC_TRY_COMPILE([#include <iostream>

                       std::ostream& operator<<(std::ostream&, struct s);],

                      [using ::operator<<; return 0;],

                      ac_cv_cxx_using_operator=1,

		      ac_cv_cxx_using_operator=0)

      AC_LANG_RESTORE])

  if test "$ac_cv_cxx_using_operator" = 1; then

    AC_DEFINE(HAVE_USING_OPERATOR, 1, [define if the compiler supports using expression for operator])

  fi])