dnl Available from the GNU Autoconf Macro Archive at:dnl http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_namespaces.htmldnlAC_DEFUN([AC_CXX_NAMESPACES],[AC_CACHE_CHECK(whether the compiler implements namespaces,ac_cv_cxx_namespaces,[AC_LANG_SAVE AC_LANG_CPLUSPLUS AC_TRY_COMPILE([namespace Outer { namespace Inner { int i = 0; }}],                [using namespace Outer::Inner; return i;], ac_cv_cxx_namespaces=yes, ac_cv_cxx_namespaces=no) AC_LANG_RESTORE])if test "$ac_cv_cxx_namespaces" = yes; then  AC_DEFINE(HAVE_NAMESPACES,,[define if the compiler implements namespaces])fi])