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// The Art of C++ / Sequences
// Copyright (c) 2015-2016 Daniel Frey
#ifndef TAOCPP_SEQUENCES_INCLUDE_SUM_HPP
#define TAOCPP_SEQUENCES_INCLUDE_SUM_HPP
#include <type_traits>
#include <utility>
#include "integer_sequence.hpp"
#include "config.hpp"
#ifndef TAOCPP_FOLD_EXPRESSIONS
#include <cstddef>
#include "make_integer_sequence.hpp"
#endif
namespace tao
{
namespace seq
{
#ifdef TAOCPP_FOLD_EXPRESSIONS
template< typename T, T... Ns >
struct sum
: std::integral_constant< T, ( Ns + ... + T( 0 ) ) >
{};
#else
namespace impl
{
template< std::size_t, std::size_t N >
struct chars
{
char dummy[ N + 1 ];
};
template< typename, std::size_t... >
struct collector;
template< std::size_t... Is, std::size_t... Ns >
struct collector< index_sequence< Is... >, Ns... >
: chars< Is, Ns >...
{};
template< std::size_t N, typename T, T... Ns >
struct sum
{
using type = std::integral_constant<
T,
T( sizeof( collector< make_index_sequence< N >, ( ( Ns > 0 ) ? Ns : 0 )... > ) - N ) -
T( sizeof( collector< make_index_sequence< N >, ( ( Ns < 0 ) ? -Ns : 0 )... > ) - N ) >;
};
}
template< typename T, T... Ns >
struct sum
: impl::sum< sizeof...( Ns ) + 1, T, Ns..., 0 >::type
{};
#endif
template< typename T, T... Ns >
struct sum< integer_sequence< T, Ns... > >
: sum< T, Ns... >
{};
}
}
#endif // TAOCPP_SEQUENCES_INCLUDE_SUM_HPP
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