#ifndef BOOST_PREPROCESSOR_CAT_HPP #define BOOST_PREPROCESSOR_CAT_HPP /* Copyright (C) 2001 * Housemarque Oy * 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. */ /**

Delays the catenation of X and Y.

For example,

  #define STATIC_ASSERT(EXPR)\
    enum\
    { BOOST_PP_CAT(static_check_,__LINE__) = (EXPR) ? 1 : -1\
    };\
    typedef char\
      BOOST_PP_CAT(static_assert_,__LINE__)\
      [ BOOST_PP_CAT(static_check_,__LINE__)\
      ]

  // ...

  STATIC_ASSERT(sizeof(int) <= sizeof(long));

expands to:

  enum
  { static_check_152 = (sizeof(int) <= sizeof(long)) ? 1 : -1
  };
  typedef char
    static_assert_152
    [ static_check_152
    ];

Using BOOST_PP_CAT() above lets the PP expand the __LINE__. If the above code would use the ## operator directly then __LINE__ would not be expanded and the above would expand to:

  enum
  { static_check___LINE__ = (sizeof(int) <= sizeof(long)) ? 1 : -1
  };
  typedef char
    static_assert___LINE__
    [ static_check___LINE__
    ];

*/ #define BOOST_PP_CAT(X,Y) BOOST_PP_CAT_DELAY(X,Y) #ifndef DOXYGEN_SHOULD_SKIP_THIS #define BOOST_PP_CAT_DELAY(X,Y) BOOST_PP_DO_CAT(X,Y) #define BOOST_PP_DO_CAT(X,Y) X##Y #endif /**

Obsolete. Use BOOST_PP_CAT().

*/ #define BOOST_PREPROCESSOR_CAT(X,Y) BOOST_PP_CAT(X,Y) #endif