CODEWITHSUNDEEP
c++boostmacrosc-preprocessor
user34537
user34537

Reputation:

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

Upvotes: 3

Views: 583

Answers (2)

Lightness Races in Orbit
Lightness Races in Orbit

Reputation: 385098

Apparently it does some auto-incrementing magic.

Here's the documentation.

I have no idea how it works. What I do know is that the magic is in counter.hpp itself; that the definition you posted has brackets in it is just so that you can write the vaguely user-friendly:

#include BOOST_PP_UPDATE_COUNTER()

to invoke said magic.

Upvotes: 6

Mat
Mat

Reputation: 206679

It's just a "shortcut" so you can do

#include BOOST_PP_UPDATE_COUNTER()

in your code rather than know the details of how that feature is implemented.

See this question Incremented define's answers for some usage example.

Upvotes: 2

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