What does #define macro() <...> do?
What does this line do?
I doubt its a template or expression. (doing those divies and naming a member hpp is a bad idea) 

    # define BOOST_PP_UPDATE_COUNTER() <boost/preprocessor/slot/detail/counter.hpp>

Full file
    
    # /* **************************************************************************
    #  *                                                                          *
    #  *     (C) Copyright Paul Mensonides 2005.                                  *
    #  *     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)                                *
    #  *                                                                          *
    #  ************************************************************************** */
    #
    # /* See http://www.boost.org for most recent version. */
    #
    # ifndef BOOST_PREPROCESSOR_SLOT_COUNTER_HPP
    # define BOOST_PREPROCESSOR_SLOT_COUNTER_HPP
    #
    # include <boost/preprocessor/slot/detail/def.hpp>
    #
    # /* BOOST_PP_COUNTER */
    #
    # define BOOST_PP_COUNTER 0
    #
    # /* BOOST_PP_UPDATE_COUNTER */
    #
    # define BOOST_PP_UPDATE_COUNTER() <boost/preprocessor/slot/detail/counter.hpp>
    #
    # endif


What does #define macro() <...> do?
===

What does this line do?
I doubt its a template or expression. (doing those divies and naming a member hpp is a bad idea) 

    # define BOOST_PP_UPDATE_COUNTER() <boost/preprocessor/slot/detail/counter.hpp>

Full file
    
    # /* **************************************************************************
    #  *                                                                          *
    #  *     (C) Copyright Paul Mensonides 2005.                                  *
    #  *     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)                                *
    #  *                                                                          *
    #  ************************************************************************** */
    #
    # /* See http://www.boost.org for most recent version. */
    #
    # ifndef BOOST_PREPROCESSOR_SLOT_COUNTER_HPP
    # define BOOST_PREPROCESSOR_SLOT_COUNTER_HPP
    #
    # include <boost/preprocessor/slot/detail/def.hpp>
    #
    # /* BOOST_PP_COUNTER */
    #
    # define BOOST_PP_COUNTER 0
    #
    # /* BOOST_PP_UPDATE_COUNTER */
    #
    # define BOOST_PP_UPDATE_COUNTER() <boost/preprocessor/slot/detail/counter.hpp>
    #
    # endif

