Add boost::optional

boost/detail/reference_content.hpp

@@ -0,0 +1,120 @@
+//-----------------------------------------------------------------------------
+// boost detail/reference_content.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_DETAIL_REFERENCE_CONTENT_HPP
+#define BOOST_DETAIL_REFERENCE_CONTENT_HPP
+
+#include "boost/config.hpp"
+
+#   include "boost/mpl/bool.hpp"
+#   include "boost/type_traits/has_nothrow_copy.hpp"
+
+#include "boost/mpl/void.hpp"
+
+namespace boost {
+
+namespace detail {
+
+///////////////////////////////////////////////////////////////////////////////
+// (detail) class template reference_content
+//
+// Non-Assignable wrapper for references.
+//
+template <typename RefT>
+class reference_content
+{
+private: // representation
+
+    RefT content_;
+
+public: // structors
+
+    ~reference_content()
+    {
+    }
+
+    reference_content(RefT r)
+        : content_( r )
+    {
+    }
+
+    reference_content(const reference_content& operand)
+        : content_( operand.content_ )
+    {
+    }
+
+private: // non-Assignable
+
+    reference_content& operator=(const reference_content&);
+
+public: // queries
+
+    RefT get() const
+    {
+        return content_;
+    }
+
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// (detail) metafunction make_reference_content
+//
+// Wraps with reference_content if specified type is reference.
+//
+
+template <typename T = mpl::void_> struct make_reference_content;
+
+
+template <typename T>
+struct make_reference_content
+{
+    typedef T type;
+};
+
+template <typename T>
+struct make_reference_content< T& >
+{
+    typedef reference_content<T&> type;
+};
+
+
+template <>
+struct make_reference_content< mpl::void_ >
+{
+    template <typename T>
+    struct apply
+        : make_reference_content<T>
+    {
+    };
+
+    typedef mpl::void_ type;
+};
+
+} // namespace detail
+
+///////////////////////////////////////////////////////////////////////////////
+// reference_content<T&> type traits specializations
+//
+
+
+template <typename T>
+struct has_nothrow_copy<
+      ::boost::detail::reference_content< T& >
+    >
+    : mpl::true_
+{
+};
+
+
+} // namespace boost
+
+#endif // BOOST_DETAIL_REFERENCE_CONTENT_HPP