# Check for hash_set extension.  This is modified from
# http://www.gnu.org/software/ac-archive/htmldoc/ac_cxx_have_ext_hash_set.html
AC_DEFUN([AC_CXX_HAVE_STD_EXT_HASH_SET],
[AC_CACHE_CHECK([whether the compiler has <ext/hash_set> defining template class std::hash_set],
 ac_cv_cxx_have_std_ext_hash_set,
 [AC_REQUIRE([AC_CXX_NAMESPACES])
  AC_LANG_SAVE
  AC_LANG_CPLUSPLUS
  AC_TRY_COMPILE([#include <ext/hash_set>
#ifdef HAVE_NAMESPACES
using namespace std;
#endif],[hash_set<int> t; ],
  [ac_cv_cxx_have_std_ext_hash_set=yes], [ac_cv_cxx_have_std_ext_hash_set=no])
  AC_LANG_RESTORE])
 HAVE_STD_EXT_HASH_SET=0
 if test "$ac_cv_cxx_have_std_ext_hash_set" = yes
 then
   HAVE_STD_EXT_HASH_SET=1
 fi
 AC_SUBST(HAVE_STD_EXT_HASH_SET)])

AC_DEFUN([AC_CXX_HAVE_GNU_EXT_HASH_SET],
[AC_CACHE_CHECK(
 [whether the compiler has <ext/hash_set> defining template class __gnu_cxx::hash_set],
 ac_cv_cxx_have_gnu_ext_hash_set,
 [AC_REQUIRE([AC_CXX_NAMESPACES])
  AC_LANG_SAVE
  AC_LANG_CPLUSPLUS
  AC_TRY_COMPILE([#include <ext/hash_set>
#ifdef HAVE_NAMESPACES
using namespace __gnu_cxx;
#endif],[hash_set<int> t; ],
  [ac_cv_cxx_have_gnu_ext_hash_set=yes], [ac_cv_cxx_have_gnu_ext_hash_set=no])
  AC_LANG_RESTORE])
 HAVE_GNU_EXT_HASH_SET=0
 if test "$ac_cv_cxx_have_gnu_ext_hash_set" = yes
 then
   HAVE_GNU_EXT_HASH_SET=1
 fi
 AC_SUBST(HAVE_GNU_EXT_HASH_SET)])

AC_DEFUN([AC_CXX_HAVE_GLOBAL_HASH_SET],
[AC_CACHE_CHECK([whether the compiler has <hash_set> defining template class ::hash_set],
 ac_cv_cxx_have_global_hash_set,
 [AC_REQUIRE([AC_CXX_NAMESPACES])
  AC_LANG_SAVE
  AC_LANG_CPLUSPLUS
  AC_TRY_COMPILE([#include <hash_set>],[hash_set<int> t; return 0;],
  [ac_cv_cxx_have_global_hash_set=yes], [ac_cv_cxx_have_global_hash_set=no])
  AC_LANG_RESTORE])
 HAVE_GLOBAL_HASH_SET=0
 if test "$ac_cv_cxx_have_global_hash_set" = yes
 then
   HAVE_GLOBAL_HASH_SET=1
 fi
 AC_SUBST(HAVE_GLOBAL_HASH_SET)])

AC_DEFUN([AC_CXX_HAVE_HASH_SET],
[AC_CXX_HAVE_STD_EXT_HASH_SET
 AC_CXX_HAVE_GNU_EXT_HASH_SET
 AC_CXX_HAVE_GLOBAL_HASH_SET])