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//  (C) Copyright Edward Diener 2011-2015
//  Use, modification and distribution are subject to the Boost Software License,
//  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at


#include <boost/vmd/detail/setup.hpp>


#include <boost/preprocessor/cat.hpp>
#include <boost/vmd/empty.hpp>


  The succeeding comments in this file are in doxygen format.


/** \file

/** \def BOOST_VMD_IDENTITY(item)

    \brief Macro which expands to its argument when invoked with any number of parameters.

    item = any single argument
    When BOOST_VMD_IDENTITY(item) is subsequently invoked with any number of parameters it expands
    to 'item'. Subsequently invoking the macro is done as 'BOOST_VMD_IDENTITY(item)(zero_or_more_arguments)'.
    The macro is equivalent to the Boost PP macro BOOST_PP_IDENTITY(item) with the difference
    being that BOOST_PP_IDENTITY(item) is always invoked with no arguments, as in
    'BOOST_VMD_IDENTITY(item)()' whereas BOOST_VMD_IDENTITY can be invoked with any number of
    The macro is meant to be used in BOOST_PP_IF and BOOST_PP_IIF statements when only one
    of the clauses needs to be invoked with calling another macro and the other is meant to
    return an 'item'.
    returns = the macro as 'BOOST_VMD_IDENTITY(item)', when invoked with any number of parameters
              as in '(zero_or_more_arguments)', returns 'item'. The macro itself returns
              'item BOOST_VMD_EMPTY'.



    \brief Macro which wraps any result which can return its value using BOOST_VMD_IDENTITY or 'item BOOST_VMD_EMPTY'.

    result = any single result returned when BOOST_VMD_IDENTITY is used or 'item BOOST_VMD_EMPTY'.
    The reason for this macro is to smooth over a problem when using VC++ with BOOST_VMD_IDENTITY.
    If your BOOST_VMD_IDENTITY macro can be used where VC++ is the compiler then you need to
    surround your macro code which could return a result with this macro in order that VC++ handles
    BOOST_VMD_IDENTITY correctly.
    If you are not using VC++ you do not have to use this macro, but doing so does no harm.

#define BOOST_VMD_IDENTITY_RESULT(result) result