initial checkin

[SVN r11780]

include/boost/preprocessor/identity.hpp

@@ -0,0 +1,44 @@
+#ifndef BOOST_PREPROCESSOR_IDENTITY_HPP
+#define BOOST_PREPROCESSOR_IDENTITY_HPP
+
+//  Copyright (C) 2001
+//  Housemarque, Inc.
+//  http://www.housemarque.com
+//  
+//  Permission to copy, use, modify, sell and distribute this software is
+//  granted provided this copyright notice appears in all copies. This
+//  software is provided "as is" without express or implied warranty, and
+//  with no claim as to its suitability for any purpose.
+
+//  See http://www.boost.org for most recent version.
+
+/*! \file
+
+<a href="../../../../boost/preprocessor/identity.hpp">Click here to see the header.</a>
+*/
+
+#ifndef BOOST_PREPROCESSOR_EMPTY_HPP
+#  include <boost/preprocessor/empty.hpp>
+#endif
+
+//! Expands to X once invoked.
+/*!
+Designed to be used with BOOST_PREPROCESSOR_IF(), when one of the clauses need to be invoked.
+
+Example:
+
+<PRE>\verbatim
+  BOOST_PREPROCESSOR_IDENTITY(X)()
+  //                            ^^ NOTE!
+\endverbatim</PRE>
+
+The above expands to:
+
+<PRE>\verbatim
+  X
+\endverbatim</PRE>
+
+NOTE: If BOOST_PREPROCESSOR_IDENTITY() is not invoked, the expansion will not be usable.
+*/
+#define BOOST_PREPROCESSOR_IDENTITY(X) X BOOST_PREPROCESSOR_EMPTY
+#endif