Renamed boost::empty to boost::blank.

[SVN r20676]

include/boost/blank.hpp

@@ -0,0 +1,84 @@
+//-----------------------------------------------------------------------------
+// boost blank.hpp header file
+// See http://www.boost.org for updates, documentation, and revision history.
+//-----------------------------------------------------------------------------
+//
+// Copyright (c) 2003
+// Eric Friedman
+//
+// Permission to use, copy, modify, distribute and sell this software
+// and its documentation for any purpose is hereby granted without fee, 
+// provided that the above copyright notice appears in all copies and 
+// that both the copyright notice and this permission notice appear in 
+// supporting documentation. No representations are made about the 
+// suitability of this software for any purpose. It is provided "as is" 
+// without express or implied warranty.
+
+#ifndef BOOST_BLANK_HPP
+#define BOOST_BLANK_HPP
+
+#include "boost/blank_fwd.hpp"
+
+#include <iosfwd> // for std::basic_ostream forward declare
+
+#include "boost/detail/templated_streams.hpp"
+#include "boost/mpl/bool.hpp"
+#include "boost/type_traits/is_empty.hpp"
+#include "boost/type_traits/is_pod.hpp"
+#include "boost/type_traits/is_stateless.hpp"
+
+namespace boost {
+
+struct blank
+{
+};
+
+// type traits specializations
+//
+
+template <>
+struct is_pod< blank >
+    : mpl::true_
+{
+};
+
+template <>
+struct is_empty< blank >
+    : mpl::true_
+{
+};
+
+template <>
+struct is_stateless< blank >
+    : mpl::true_
+{
+};
+
+// relational operators
+//
+
+inline bool operator==(const blank&, const blank&)
+{
+    return true;
+}
+
+inline bool operator<(const blank&, const blank&)
+{
+    return false;
+}
+
+// streaming support
+//
+BOOST_TEMPLATED_STREAM_TEMPLATE(E,T)
+inline BOOST_TEMPLATED_STREAM(ostream, E,T)& operator<<(
+      BOOST_TEMPLATED_STREAM(ostream, E,T)& out
+    , const blank&
+    )
+{
+    // (output nothing)
+    return out;
+}
+
+} // namespace boost
+
+#endif // BOOST_BLANK_HPP