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// The Art of C++ / Sequences
// Copyright (c) 2015 Daniel Frey
#ifndef TAOCPP_SEQUENCES_INCLUDE_MAKE_INTEGER_SEQUENCE_HPP
#define TAOCPP_SEQUENCES_INCLUDE_MAKE_INTEGER_SEQUENCE_HPP
#include <cstddef>
#include <utility>
#include <type_traits>
#include "config.hpp"
#include "integer_sequence.hpp"
namespace tao
{
namespace seq
{
#ifdef TAOCPP_USE_STD_MAKE_INTEGER_SEQUENCE
using std::make_integer_sequence;
using std::make_index_sequence;
using std::index_sequence_for;
#else
// idea from http://stackoverflow.com/a/13073076
namespace impl
{
template< typename, std::size_t, bool >
struct double_up;
template< typename T, T... Ns, std::size_t N >
struct double_up< integer_sequence< T, Ns... >, N, false >
{
using type = integer_sequence< T, Ns..., ( N + Ns )... >;
};
template< typename T, T... Ns, std::size_t N >
struct double_up< integer_sequence< T, Ns... >, N, true >
{
using type = integer_sequence< T, Ns..., ( N + Ns )..., 2 * N >;
};
template< typename T, T N, typename = void >
struct generate;
template< typename T, T N >
using generate_t = typename generate< T, N >::type;
template< typename T, T N, typename >
struct generate
: double_up< generate_t< T, N / 2 >, N / 2, N % 2 == 1 >
{};
template< typename T, T N >
struct generate< T, N, typename std::enable_if< ( N == 0 ) >::type >
{
using type = integer_sequence< T >;
};
template< typename T, T N >
struct generate< T, N, typename std::enable_if< ( N == 1 ) >::type >
{
using type = integer_sequence< T, 0 >;
};
}
template< typename T, T N >
using make_integer_sequence = impl::generate_t< T, N >;
template< std::size_t N >
using make_index_sequence = make_integer_sequence< std::size_t, N >;
template< typename... Ts >
using index_sequence_for = make_index_sequence< sizeof...( Ts ) >;
#endif
}
}
#endif // TAOCPP_SEQUENCES_INCLUDE_MAKE_INTEGER_SEQUENCE_HPP
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