Add boost::variant

boost/blank.hpp

@@ -0,0 +1,106 @@
+//-----------------------------------------------------------------------------
+// boost blank.hpp header file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2003
+// Eric Friedman
+//
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+
+#ifndef BOOST_BLANK_HPP
+#define BOOST_BLANK_HPP
+
+#include "boost/blank_fwd.hpp"
+
+#if !defined(BOOST_NO_IOSTREAM)
+#include <iosfwd> // for std::basic_ostream forward declare
+#include "boost/detail/templated_streams.hpp"
+#endif // BOOST_NO_IOSTREAM
+
+#include "boost/mpl/bool.hpp"
+#include "boost/type_traits/is_empty.hpp"
+#include "boost/type_traits/is_pod.hpp"
+#include "boost/type_traits/is_stateless.hpp"
+
+namespace boost {
+
+struct blank
+{
+};
+
+// type traits specializations
+//
+
+template <>
+struct is_pod< blank >
+    : mpl::true_
+{
+};
+
+template <>
+struct is_empty< blank >
+    : mpl::true_
+{
+};
+
+template <>
+struct is_stateless< blank >
+    : mpl::true_
+{
+};
+
+// relational operators
+//
+
+inline bool operator==(const blank&, const blank&)
+{
+    return true;
+}
+
+inline bool operator<=(const blank&, const blank&)
+{
+    return true;
+}
+
+inline bool operator>=(const blank&, const blank&)
+{
+    return true;
+}
+
+inline bool operator!=(const blank&, const blank&)
+{
+    return false;
+}
+
+inline bool operator<(const blank&, const blank&)
+{
+    return false;
+}
+
+inline bool operator>(const blank&, const blank&)
+{
+    return false;
+}
+
+// streaming support
+//
+#if !defined(BOOST_NO_IOSTREAM)
+
+BOOST_TEMPLATED_STREAM_TEMPLATE(E,T)
+inline BOOST_TEMPLATED_STREAM(ostream, E,T)& operator<<(
+      BOOST_TEMPLATED_STREAM(ostream, E,T)& out
+    , const blank&
+    )
+{
+    // (output nothing)
+    return out;
+}
+
+#endif // BOOST_NO_IOSTREAM
+
+} // namespace boost
+
+#endif // BOOST_BLANK_HPP