Add boost::variant

boost/variant/recursive_wrapper_fwd.hpp

@@ -0,0 +1,103 @@
+//-----------------------------------------------------------------------------
+// boost variant/recursive_wrapper_fwd.hpp header file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2002
+// Eric Friedman, Itay Maman
+//
+// Portions Copyright (C) 2002 David Abrahams
+//
+// 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_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
+#define BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP
+
+#include "boost/mpl/aux_/config/ctps.hpp"
+
+#include "boost/mpl/aux_/lambda_support.hpp"
+
+// should be the last #include
+#include "boost/type_traits/detail/bool_trait_def.hpp"
+
+namespace boost {
+
+//////////////////////////////////////////////////////////////////////////
+// class template recursive_wrapper
+//
+// Enables recursive types in templates by breaking cyclic dependencies.
+//
+// For example:
+//
+//   class my;
+//
+//   typedef variant< int, recursive_wrapper<my> > var;
+//
+//   class my {
+//     var var_;
+//     ...
+//   };
+//
+template <typename T> class recursive_wrapper;
+
+///////////////////////////////////////////////////////////////////////////////
+// metafunction is_recursive_wrapper (modeled on code by David Abrahams)
+//
+// True iff specified type matches recursive_wrapper<T>.
+//
+
+namespace detail {
+
+
+template <typename T>
+struct is_recursive_wrapper_impl
+    : mpl::false_
+{
+};
+
+template <typename T>
+struct is_recursive_wrapper_impl< recursive_wrapper<T> >
+    : mpl::true_
+{
+};
+
+
+} // namespace detail
+
+BOOST_TT_AUX_BOOL_TRAIT_DEF1(
+      is_recursive_wrapper
+    , T
+    , (::boost::detail::is_recursive_wrapper_impl<T>::value)
+    )
+
+///////////////////////////////////////////////////////////////////////////////
+// metafunction unwrap_recursive
+//
+// If specified type T matches recursive_wrapper<U>, then U; else T.
+//
+
+
+template <typename T>
+struct unwrap_recursive
+{
+    typedef T type;
+
+    BOOST_MPL_AUX_LAMBDA_SUPPORT(1,unwrap_recursive,(T))
+};
+
+template <typename T>
+struct unwrap_recursive< recursive_wrapper<T> >
+{
+    typedef T type;
+
+    BOOST_MPL_AUX_LAMBDA_SUPPORT_SPEC(1,unwrap_recursive,(T))
+};
+
+
+} // namespace boost
+
+#include "boost/type_traits/detail/bool_trait_undef.hpp"
+
+#endif // BOOST_VARIANT_RECURSIVE_WRAPPER_FWD_HPP