Imported Upstream version 1.49.0upstream/1.49.0

1 files changed, 61 insertions, 0 deletions

diff --git a/boost/phoenix/core/nothing.hpp b/boost/phoenix/core/nothing.hpp
new file mode 100644
index 0000000000..c63c43aba0
--- /dev/null
+++ b/boost/phoenix/core/nothing.hpp
@@ -0,0 +1,61 @@
+/*==============================================================================
+    Copyright (c) 2005-2010 Joel de Guzman
+
+    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_PHOENIX_CORE_NOTHING_HPP
+#define BOOST_PHOENIX_CORE_NOTHING_HPP
+
+#include <boost/phoenix/core/limits.hpp>
+#include <boost/mpl/void.hpp>
+#include <boost/phoenix/core/actor.hpp>
+#include <boost/phoenix/core/call.hpp>
+#include <boost/phoenix/core/expression.hpp>
+#include <boost/phoenix/core/value.hpp>
+
+namespace boost { namespace phoenix
+{
+    /////////////////////////////////////////////////////////////////////////////
+    //
+    //  null_actor
+    //
+    //      An actor that does nothing (a "bum", if you will :-).
+    //
+    /////////////////////////////////////////////////////////////////////////////
+    
+    namespace detail
+    {
+        struct nothing {};
+    }
+    
+    namespace expression
+    {
+        struct null
+            : expression::value<detail::nothing>
+        {};
+    }
+    
+    template<typename Dummy>
+    struct is_custom_terminal<detail::nothing, Dummy>
+      : mpl::true_
+    {};
+
+    template<typename Dummy>
+    struct custom_terminal<detail::nothing, Dummy>
+    {
+        typedef void result_type;
+
+        template <typename Context>
+        void operator()(detail::nothing, Context &) const
+        {
+        }
+    };
+
+    typedef expression::null::type nothing_type;
+#ifndef BOOST_PHOENIX_NO_PREDEFINED_TERMINALS
+    nothing_type const nothing = {{{}}};
+#endif
+}}
+
+#endif