unused entries in zip

[SVN r37150]

include/boost/fusion/support/unused.hpp

@@ -0,0 +1,62 @@
+/*=============================================================================
+    Copyright (c) 2001-2006 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)
+==============================================================================*/
+#if !defined(BOOST_FUSION_SUPPORT_UNUSED_20070305_1038)
+#define BOOST_FUSION_SUPPORT_UNUSED_20070305_1038
+
+#include <boost/config.hpp>
+#if defined(BOOST_MSVC)
+# pragma warning(push)
+# pragma warning(disable: 4522) // multiple assignment operators specified warning
+#endif
+
+namespace boost { namespace fusion {
+    struct unused_type
+    {
+        unused_type()
+        {
+        }
+
+        template <typename T>
+        unused_type(T const&)
+        {
+        }
+
+        template <typename T>
+        unused_type const&
+        operator=(T const&) const
+        {
+            return *this;
+        }
+
+        template <typename T>
+        unused_type&
+        operator=(T const&)
+        {
+            return *this;
+        }
+
+        unused_type const&
+        operator=(unused_type const&) const
+        {
+            return *this;
+        }
+
+        unused_type&
+        operator=(unused_type const&)
+        {
+            return *this;
+        }
+    };
+
+    unused_type const unused = unused_type();
+}}
+
+#if defined(BOOST_MSVC)
+# pragma warning(pop)
+#endif
+
+#endif