# Boost C++ Libraries

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### boost/vmd/is_empty_array.hpp


//  (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

#if !defined(BOOST_VMD_IS_EMPTY_ARRAY_HPP)
#define BOOST_VMD_IS_EMPTY_ARRAY_HPP

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

#include <boost/preprocessor/control/iif.hpp>
#include <boost/vmd/is_array.hpp>
#include <boost/vmd/identity.hpp>
#include <boost/vmd/detail/is_empty_array.hpp>

/*

The succeeding comments in this file are in doxygen format.

*/

/** \file
*/

/** \def BOOST_VMD_IS_EMPTY_ARRAY(sequence)

\brief Tests whether a sequence is an empty Boost PP array.

An empty Boost PP array is a two element tuple where the first
size element is 0 and the second element is a tuple with a single
empty element, ie. '(0,())'.

sequence = a possible empty array

returns = 1 if the sequence is an empty Boost PP array
0 if it is not.

The macro will generate a preprocessing error if the sequence
is in the form of an array but its first tuple element, instead
of being a number, is a preprocessor token which VMD cannot parse,
as in the example '(&0,())' which is a valid tuple but an invalid
array.

*/

#define BOOST_VMD_IS_EMPTY_ARRAY(sequence) \
BOOST_VMD_IDENTITY_RESULT \
( \
BOOST_PP_IIF \
( \
BOOST_VMD_IS_ARRAY(sequence), \
BOOST_VMD_DETAIL_IS_EMPTY_ARRAY_SIZE, \
BOOST_VMD_IDENTITY(0) \
) \
(sequence) \
) \
/**/

/** \def BOOST_VMD_IS_EMPTY_ARRAY_D(d,sequence)

\brief Tests whether a sequence is an empty Boost PP array. Re-entrant version.

An empty Boost PP array is a two element tuple where the first
size element is 0 and the second element is a tuple with a single
empty element, ie. '(0,())'.

d        = The next available BOOST_PP_WHILE iteration.
sequence = a possible empty array

returns = 1 if the sequence is an empty Boost PP array
0 if it is not.

The macro will generate a preprocessing error if the sequence
is in the form of an array but its first tuple element, instead
of being a number, is a preprocessor token which VMD cannot parse,
as in the example '(&0,())' which is a valid tuple but an invalid
array.

*/

#define BOOST_VMD_IS_EMPTY_ARRAY_D(d,sequence) \
BOOST_VMD_IDENTITY_RESULT \
( \
BOOST_PP_IIF \
( \
BOOST_VMD_IS_ARRAY_D(d,sequence), \
BOOST_VMD_DETAIL_IS_EMPTY_ARRAY_SIZE, \
BOOST_VMD_IDENTITY(0) \
) \
(sequence) \
) \
/**/