add 'is_even' metafunction

[SVN r16418]

include/boost/mpl/math/is_even.hpp

@@ -0,0 +1,44 @@
+//-----------------------------------------------------------------------------
+// boost/mpl/is_even.hpp header file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2000-01
+// Aleksey Gurtovoy
+//
+// Permission to use, copy, modify, distribute and sell this software
+// and its documentation for any purpose is hereby granted without fee, 
+// provided that the above copyright notice appears in all copies and 
+// that both the copyright notice and this permission notice appear in 
+// supporting documentation. No representations are made about the 
+// suitability of this software for any purpose. It is provided "as is" 
+// without express or implied warranty.
+
+#ifndef BOOST_MPL_MATH_IS_EVEN_HPP_INCLUDED
+#define BOOST_MPL_MATH_IS_EVEN_HPP_INCLUDED
+
+#include "boost/mpl/bool_c.hpp"
+#include "boost/mpl/aux_/void_spec.hpp"
+#include "boost/mpl/aux_/lambda_support.hpp"
+#include "boost/mpl/aux_/config/eti.hpp"
+
+namespace boost { namespace mpl {
+
+namespace math {
+
+template<
+      typename BOOST_MPL_AUX_VOID_SPEC_PARAM(N)
+    >
+struct is_even
+    : bool_c<((N::value % 2) == 0)>
+{
+    BOOST_MPL_AUX_LAMBDA_SUPPORT(1,is_even,(N))
+};
+
+} // namespace math
+
+BOOST_MPL_AUX_VOID_SPEC(1, math::is_even)
+
+}} // namespace boost::mpl
+
+#endif // BOOST_MPL_MATH_IS_EVEN_HPP_INCLUDED