2f983fa690
The spaceship operator for std::array uses memcmp when the __is_byte<value_type> trait is true, but memcmp isn't usable in constexpr contexts. Also, memcmp should only be used for unsigned byte types, because it gives the wrong answer for signed chars with negative values. We can simply check std::is_constant_evaluated() so that we don't use memcmp during constant evaluation. To fix the problem of using memcmp for inappropriate types, this patch adds new __is_memcmp_ordered and __is_memcmp_ordered_with traits. These say whether using memcmp will give the right answer for ordering operations such as lexicographical_compare and three-way comparisons. The new traits can be used in several places, and can also be used to implement my suggestion in PR 93059 comment 37 to use memcmp for unsigned integers larger than one byte on big endian targets. libstdc++-v3/ChangeLog: PR libstdc++/96851 * include/bits/cpp_type_traits.h (__is_memcmp_ordered): New trait that says if memcmp can be used for ordering. (__is_memcmp_ordered_with): Likewise, for two types. * include/bits/deque.tcc (__lex_cmp_dit): Use new traits instead of __is_byte and __numeric_traits. (__lexicographical_compare_aux1): Likewise. * include/bits/ranges_algo.h (__lexicographical_compare_fn): Likewise. * include/bits/stl_algobase.h (__lexicographical_compare_aux1) (__is_byte_iter): Likewise. * include/std/array (operator<=>): Likewise. Only use memcmp when std::is_constant_evaluated() is false. * testsuite/23_containers/array/comparison_operators/96851.cc: New test. * testsuite/23_containers/array/tuple_interface/get_neg.cc: Adjust dg-error line numbers.
452 lines
14 KiB
C++
452 lines
14 KiB
C++
// <array> -*- C++ -*-
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// Copyright (C) 2007-2020 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// Under Section 7 of GPL version 3, you are granted additional
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// permissions described in the GCC Runtime Library Exception, version
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// 3.1, as published by the Free Software Foundation.
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// You should have received a copy of the GNU General Public License and
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// a copy of the GCC Runtime Library Exception along with this program;
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// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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// <http://www.gnu.org/licenses/>.
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/** @file include/array
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* This is a Standard C++ Library header.
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*/
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#ifndef _GLIBCXX_ARRAY
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#define _GLIBCXX_ARRAY 1
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#pragma GCC system_header
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#if __cplusplus < 201103L
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# include <bits/c++0x_warning.h>
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#else
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#include <utility>
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#include <bits/functexcept.h>
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#include <bits/stl_algobase.h>
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#include <bits/range_access.h>
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_CONTAINER
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template<typename _Tp, std::size_t _Nm>
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struct __array_traits
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{
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typedef _Tp _Type[_Nm];
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typedef __is_swappable<_Tp> _Is_swappable;
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typedef __is_nothrow_swappable<_Tp> _Is_nothrow_swappable;
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static constexpr _Tp&
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_S_ref(const _Type& __t, std::size_t __n) noexcept
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{ return const_cast<_Tp&>(__t[__n]); }
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static constexpr _Tp*
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_S_ptr(const _Type& __t) noexcept
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{ return const_cast<_Tp*>(__t); }
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};
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template<typename _Tp>
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struct __array_traits<_Tp, 0>
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{
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struct _Type { };
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typedef true_type _Is_swappable;
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typedef true_type _Is_nothrow_swappable;
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static constexpr _Tp&
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_S_ref(const _Type&, std::size_t) noexcept
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{ return *static_cast<_Tp*>(nullptr); }
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static constexpr _Tp*
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_S_ptr(const _Type&) noexcept
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{ return nullptr; }
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};
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/**
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* @brief A standard container for storing a fixed size sequence of elements.
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*
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* @ingroup sequences
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*
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* Meets the requirements of a <a href="tables.html#65">container</a>, a
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* <a href="tables.html#66">reversible container</a>, and a
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* <a href="tables.html#67">sequence</a>.
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*
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* Sets support random access iterators.
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*
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* @tparam Tp Type of element. Required to be a complete type.
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* @tparam Nm Number of elements.
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*/
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template<typename _Tp, std::size_t _Nm>
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struct array
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{
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typedef _Tp value_type;
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typedef value_type* pointer;
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typedef const value_type* const_pointer;
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typedef value_type& reference;
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typedef const value_type& const_reference;
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typedef value_type* iterator;
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typedef const value_type* const_iterator;
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typedef std::size_t size_type;
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typedef std::ptrdiff_t difference_type;
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typedef std::reverse_iterator<iterator> reverse_iterator;
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typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
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// Support for zero-sized arrays mandatory.
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typedef _GLIBCXX_STD_C::__array_traits<_Tp, _Nm> _AT_Type;
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typename _AT_Type::_Type _M_elems;
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// No explicit construct/copy/destroy for aggregate type.
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// DR 776.
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_GLIBCXX20_CONSTEXPR void
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fill(const value_type& __u)
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{ std::fill_n(begin(), size(), __u); }
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_GLIBCXX20_CONSTEXPR void
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swap(array& __other)
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noexcept(_AT_Type::_Is_nothrow_swappable::value)
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{ std::swap_ranges(begin(), end(), __other.begin()); }
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// Iterators.
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_GLIBCXX17_CONSTEXPR iterator
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begin() noexcept
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{ return iterator(data()); }
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_GLIBCXX17_CONSTEXPR const_iterator
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begin() const noexcept
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{ return const_iterator(data()); }
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_GLIBCXX17_CONSTEXPR iterator
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end() noexcept
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{ return iterator(data() + _Nm); }
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_GLIBCXX17_CONSTEXPR const_iterator
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end() const noexcept
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{ return const_iterator(data() + _Nm); }
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_GLIBCXX17_CONSTEXPR reverse_iterator
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rbegin() noexcept
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{ return reverse_iterator(end()); }
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_GLIBCXX17_CONSTEXPR const_reverse_iterator
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rbegin() const noexcept
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{ return const_reverse_iterator(end()); }
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_GLIBCXX17_CONSTEXPR reverse_iterator
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rend() noexcept
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{ return reverse_iterator(begin()); }
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_GLIBCXX17_CONSTEXPR const_reverse_iterator
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rend() const noexcept
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{ return const_reverse_iterator(begin()); }
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_GLIBCXX17_CONSTEXPR const_iterator
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cbegin() const noexcept
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{ return const_iterator(data()); }
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_GLIBCXX17_CONSTEXPR const_iterator
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cend() const noexcept
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{ return const_iterator(data() + _Nm); }
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_GLIBCXX17_CONSTEXPR const_reverse_iterator
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crbegin() const noexcept
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{ return const_reverse_iterator(end()); }
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_GLIBCXX17_CONSTEXPR const_reverse_iterator
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crend() const noexcept
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{ return const_reverse_iterator(begin()); }
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// Capacity.
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constexpr size_type
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size() const noexcept { return _Nm; }
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constexpr size_type
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max_size() const noexcept { return _Nm; }
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_GLIBCXX_NODISCARD constexpr bool
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empty() const noexcept { return size() == 0; }
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// Element access.
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_GLIBCXX17_CONSTEXPR reference
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operator[](size_type __n) noexcept
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{ return _AT_Type::_S_ref(_M_elems, __n); }
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constexpr const_reference
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operator[](size_type __n) const noexcept
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{ return _AT_Type::_S_ref(_M_elems, __n); }
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_GLIBCXX17_CONSTEXPR reference
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at(size_type __n)
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{
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if (__n >= _Nm)
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std::__throw_out_of_range_fmt(__N("array::at: __n (which is %zu) "
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">= _Nm (which is %zu)"),
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__n, _Nm);
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return _AT_Type::_S_ref(_M_elems, __n);
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}
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constexpr const_reference
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at(size_type __n) const
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{
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// Result of conditional expression must be an lvalue so use
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// boolean ? lvalue : (throw-expr, lvalue)
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return __n < _Nm ? _AT_Type::_S_ref(_M_elems, __n)
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: (std::__throw_out_of_range_fmt(__N("array::at: __n (which is %zu) "
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">= _Nm (which is %zu)"),
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__n, _Nm),
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_AT_Type::_S_ref(_M_elems, 0));
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}
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_GLIBCXX17_CONSTEXPR reference
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front() noexcept
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{ return *begin(); }
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constexpr const_reference
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front() const noexcept
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{ return _AT_Type::_S_ref(_M_elems, 0); }
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_GLIBCXX17_CONSTEXPR reference
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back() noexcept
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{ return _Nm ? *(end() - 1) : *end(); }
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constexpr const_reference
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back() const noexcept
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{
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return _Nm ? _AT_Type::_S_ref(_M_elems, _Nm - 1)
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: _AT_Type::_S_ref(_M_elems, 0);
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}
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_GLIBCXX17_CONSTEXPR pointer
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data() noexcept
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{ return _AT_Type::_S_ptr(_M_elems); }
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_GLIBCXX17_CONSTEXPR const_pointer
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data() const noexcept
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{ return _AT_Type::_S_ptr(_M_elems); }
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};
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#if __cpp_deduction_guides >= 201606
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template<typename _Tp, typename... _Up>
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array(_Tp, _Up...)
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-> array<enable_if_t<(is_same_v<_Tp, _Up> && ...), _Tp>,
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1 + sizeof...(_Up)>;
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#endif
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// Array comparisons.
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline bool
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operator==(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
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{ return std::equal(__one.begin(), __one.end(), __two.begin()); }
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#if __cpp_lib_three_way_comparison && __cpp_lib_concepts
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template<typename _Tp, size_t _Nm>
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constexpr __detail::__synth3way_t<_Tp>
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operator<=>(const array<_Tp, _Nm>& __a, const array<_Tp, _Nm>& __b)
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{
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#ifdef __cpp_lib_is_constant_evaluated
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if constexpr (_Nm && __is_memcmp_ordered<_Tp>::__value)
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if (!std::is_constant_evaluated())
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{
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constexpr size_t __n = _Nm * sizeof(_Tp);
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return __builtin_memcmp(__a.data(), __b.data(), __n) <=> 0;
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}
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#endif
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for (size_t __i = 0; __i < _Nm; ++__i)
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{
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auto __c = __detail::__synth3way(__a[__i], __b[__i]);
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if (__c != 0)
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return __c;
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}
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return strong_ordering::equal;
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}
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#else
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline bool
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operator!=(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
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{ return !(__one == __two); }
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline bool
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operator<(const array<_Tp, _Nm>& __a, const array<_Tp, _Nm>& __b)
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{
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return std::lexicographical_compare(__a.begin(), __a.end(),
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__b.begin(), __b.end());
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}
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline bool
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operator>(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
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{ return __two < __one; }
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline bool
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operator<=(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
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{ return !(__one > __two); }
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline bool
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operator>=(const array<_Tp, _Nm>& __one, const array<_Tp, _Nm>& __two)
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{ return !(__one < __two); }
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#endif // three_way_comparison && concepts
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// Specialized algorithms.
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template<typename _Tp, std::size_t _Nm>
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_GLIBCXX20_CONSTEXPR
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inline
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#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
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// Constrained free swap overload, see p0185r1
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typename enable_if<
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_GLIBCXX_STD_C::__array_traits<_Tp, _Nm>::_Is_swappable::value
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>::type
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#else
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void
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#endif
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swap(array<_Tp, _Nm>& __one, array<_Tp, _Nm>& __two)
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noexcept(noexcept(__one.swap(__two)))
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{ __one.swap(__two); }
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#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
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template<typename _Tp, std::size_t _Nm>
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typename enable_if<
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!_GLIBCXX_STD_C::__array_traits<_Tp, _Nm>::_Is_swappable::value>::type
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swap(array<_Tp, _Nm>&, array<_Tp, _Nm>&) = delete;
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#endif
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template<std::size_t _Int, typename _Tp, std::size_t _Nm>
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constexpr _Tp&
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get(array<_Tp, _Nm>& __arr) noexcept
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{
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static_assert(_Int < _Nm, "array index is within bounds");
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return _GLIBCXX_STD_C::__array_traits<_Tp, _Nm>::
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_S_ref(__arr._M_elems, _Int);
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}
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template<std::size_t _Int, typename _Tp, std::size_t _Nm>
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constexpr _Tp&&
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get(array<_Tp, _Nm>&& __arr) noexcept
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{
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static_assert(_Int < _Nm, "array index is within bounds");
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return std::move(_GLIBCXX_STD_C::get<_Int>(__arr));
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}
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template<std::size_t _Int, typename _Tp, std::size_t _Nm>
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constexpr const _Tp&
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get(const array<_Tp, _Nm>& __arr) noexcept
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{
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static_assert(_Int < _Nm, "array index is within bounds");
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return _GLIBCXX_STD_C::__array_traits<_Tp, _Nm>::
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_S_ref(__arr._M_elems, _Int);
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}
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template<std::size_t _Int, typename _Tp, std::size_t _Nm>
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constexpr const _Tp&&
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get(const array<_Tp, _Nm>&& __arr) noexcept
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{
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static_assert(_Int < _Nm, "array index is within bounds");
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return std::move(_GLIBCXX_STD_C::get<_Int>(__arr));
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}
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#if __cplusplus > 201703L
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#define __cpp_lib_to_array 201907L
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template<bool _Move = false, typename _Tp, size_t... _Idx>
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constexpr array<remove_cv_t<_Tp>, sizeof...(_Idx)>
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__to_array(_Tp (&__a)[sizeof...(_Idx)], index_sequence<_Idx...>)
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{
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if constexpr (_Move)
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return {{std::move(__a[_Idx])...}};
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else
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return {{__a[_Idx]...}};
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}
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template<typename _Tp, size_t _Nm>
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constexpr array<remove_cv_t<_Tp>, _Nm>
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to_array(_Tp (&__a)[_Nm])
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noexcept(is_nothrow_constructible_v<_Tp, _Tp&>)
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{
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static_assert(!is_array_v<_Tp>);
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static_assert(is_constructible_v<_Tp, _Tp&>);
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if constexpr (is_constructible_v<_Tp, _Tp&>)
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return _GLIBCXX_STD_C::__to_array(__a, make_index_sequence<_Nm>{});
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__builtin_unreachable(); // FIXME: see PR c++/91388
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}
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template<typename _Tp, size_t _Nm>
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constexpr array<remove_cv_t<_Tp>, _Nm>
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to_array(_Tp (&&__a)[_Nm])
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noexcept(is_nothrow_move_constructible_v<_Tp>)
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{
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static_assert(!is_array_v<_Tp>);
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static_assert(is_move_constructible_v<_Tp>);
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if constexpr (is_move_constructible_v<_Tp>)
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return _GLIBCXX_STD_C::__to_array<1>(__a, make_index_sequence<_Nm>{});
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__builtin_unreachable(); // FIXME: see PR c++/91388
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}
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#endif // C++20
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_GLIBCXX_END_NAMESPACE_CONTAINER
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} // namespace std
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namespace std _GLIBCXX_VISIBILITY(default)
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{
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_GLIBCXX_BEGIN_NAMESPACE_VERSION
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// Tuple interface to class template array.
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/// tuple_size
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template<typename _Tp>
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struct tuple_size;
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/// Partial specialization for std::array
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template<typename _Tp, std::size_t _Nm>
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struct tuple_size<_GLIBCXX_STD_C::array<_Tp, _Nm>>
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: public integral_constant<std::size_t, _Nm> { };
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/// tuple_element
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template<std::size_t _Int, typename _Tp>
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struct tuple_element;
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/// Partial specialization for std::array
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template<std::size_t _Int, typename _Tp, std::size_t _Nm>
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struct tuple_element<_Int, _GLIBCXX_STD_C::array<_Tp, _Nm>>
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{
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static_assert(_Int < _Nm, "index is out of bounds");
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typedef _Tp type;
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};
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template<typename _Tp, std::size_t _Nm>
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struct __is_tuple_like_impl<_GLIBCXX_STD_C::array<_Tp, _Nm>> : true_type
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{ };
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_GLIBCXX_END_NAMESPACE_VERSION
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} // namespace std
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#ifdef _GLIBCXX_DEBUG
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# include <debug/array>
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#endif
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#endif // C++11
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#endif // _GLIBCXX_ARRAY
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