initial checkin

[SVN r11780]

include/boost/preprocessor/cat.hpp

@@ -0,0 +1,70 @@
+#ifndef BOOST_PREPROCESSOR_CAT_HPP
+#define BOOST_PREPROCESSOR_CAT_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/cat.hpp">Click here to see the header.</a>
+*/
+
+//! Delays the catenation of L and R.
+/*!
+Example:
+
+<PRE>\verbatim
+  #define STATIC_ASSERT(EXPR)\
+    enum\
+    { BOOST_PREPROCESSOR_CAT(static_check_,__LINE__) = (EXPR) ? 1 : -1\
+    };\
+    typedef char\
+      BOOST_PREPROCESSOR_CAT(static_assert_,__LINE__)\
+      [ BOOST_PREPROCESSOR_CAT(static_check_,__LINE__)\
+      ]
+
+  // ...
+
+  STATIC_ASSERT(sizeof(int) <= sizeof(long));
+\endverbatim</PRE>
+
+The above expands to:
+
+<PRE>\verbatim
+  enum
+  { static_check_152 = (sizeof(int) <= sizeof(long)) ? 1 : -1
+  };
+  typedef char
+    static_assert_152
+    [ static_check_152
+    ];
+\endverbatim</PRE>
+
+Using BOOST_PREPROCESSOR_CAT() above lets the preprocessor expand the __LINE__.
+If the above code would use the ## operator directly then __LINE__ would not be
+expanded and the above would expand to:
+
+<PRE>\verbatim
+  enum
+  { static_check___LINE__ = (sizeof(int) <= sizeof(long)) ? 1 : -1
+  };
+  typedef char
+    static_assert___LINE__
+    [ static_check___LINE__
+    ];
+\endverbatim</PRE>
+*/
+#define BOOST_PREPROCESSOR_CAT(L,R) BOOST_PREPROCESSOR_CAT_DELAY(L,R)
+
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
+#define BOOST_PREPROCESSOR_CAT_DELAY(L,R) L##R
+#endif /* DOXYGEN_SHOULD_SKIP_THIS */
+#endif