xref: /llvm-project-15.0.7/libcxx/include/tuple (revision 2bb3a906)
1// -*- C++ -*-
2//===--------------------------- tuple ------------------------------------===//
3//
4//                     The LLVM Compiler Infrastructure
5//
6// This file is distributed under the University of Illinois Open Source
7// License. See LICENSE.TXT for details.
8//
9//===----------------------------------------------------------------------===//
10
11#ifndef _LIBCPP_TUPLE
12#define _LIBCPP_TUPLE
13
14/*
15    tuple synopsis
16
17namespace std
18{
19
20template <class... T>
21class tuple {
22public:
23    constexpr tuple();
24    explicit tuple(const T&...);  // constexpr in C++14
25    template <class... U>
26        explicit tuple(U&&...);  // constexpr in C++14
27    tuple(const tuple&) = default;
28    tuple(tuple&&) = default;
29    template <class... U>
30        tuple(const tuple<U...>&);  // constexpr in C++14
31    template <class... U>
32        tuple(tuple<U...>&&);  // constexpr in C++14
33    template <class U1, class U2>
34        tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2 // constexpr in C++14
35    template <class U1, class U2>
36        tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2  // constexpr in C++14
37
38    // allocator-extended constructors
39    template <class Alloc>
40        tuple(allocator_arg_t, const Alloc& a);
41    template <class Alloc>
42        tuple(allocator_arg_t, const Alloc& a, const T&...);
43    template <class Alloc, class... U>
44        tuple(allocator_arg_t, const Alloc& a, U&&...);
45    template <class Alloc>
46        tuple(allocator_arg_t, const Alloc& a, const tuple&);
47    template <class Alloc>
48        tuple(allocator_arg_t, const Alloc& a, tuple&&);
49    template <class Alloc, class... U>
50        tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);
51    template <class Alloc, class... U>
52        tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);
53    template <class Alloc, class U1, class U2>
54        tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);
55    template <class Alloc, class U1, class U2>
56        tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);
57
58    tuple& operator=(const tuple&);
59    tuple&
60        operator=(tuple&&) noexcept(AND(is_nothrow_move_assignable<T>::value ...));
61    template <class... U>
62        tuple& operator=(const tuple<U...>&);
63    template <class... U>
64        tuple& operator=(tuple<U...>&&);
65    template <class U1, class U2>
66        tuple& operator=(const pair<U1, U2>&); // iff sizeof...(T) == 2
67    template <class U1, class U2>
68        tuple& operator=(pair<U1, U2>&&); //iffsizeof...(T) == 2
69
70    void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));
71};
72
73const unspecified ignore;
74
75template <class... T> tuple<V...>  make_tuple(T&&...); // constexpr in C++14
76template <class... T> tuple<ATypes...> forward_as_tuple(T&&...) noexcept; // constexpr in C++14
77template <class... T> tuple<T&...> tie(T&...) noexcept; // constexpr in C++14
78template <class... Tuples> tuple<CTypes...> tuple_cat(Tuples&&... tpls); // constexpr in C++14
79
80// 20.4.1.4, tuple helper classes:
81template <class T> class tuple_size; // undefined
82template <class... T> class tuple_size<tuple<T...>>;
83template <intsize_t I, class T> class tuple_element; // undefined
84template <intsize_t I, class... T> class tuple_element<I, tuple<T...>>;
85template <size_t _Ip, class ..._Tp>
86  using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type; // C++14
87
88// 20.4.1.5, element access:
89template <intsize_t I, class... T>
90    typename tuple_element<I, tuple<T...>>::type&
91    get(tuple<T...>&) noexcept; // constexpr in C++14
92template <intsize_t I, class... T>
93    typename const tuple_element<I, tuple<T...>>::type &
94    get(const tuple<T...>&) noexcept; // constexpr in C++14
95template <intsize_t I, class... T>
96    typename tuple_element<I, tuple<T...>>::type&&
97    get(tuple<T...>&&) noexcept; // constexpr in C++14
98
99template <class T1, class... T>
100    constexpr T1& get(tuple<T...>&) noexcept;  // C++14
101template <class T1, class... T>
102    constexpr T1 const& get(const tuple<T...>&) noexcept;   // C++14
103template <class T1, class... T>
104    constexpr T1&& get(tuple<T...>&&) noexcept;   // C++14
105
106// 20.4.1.6, relational operators:
107template<class... T, class... U> bool operator==(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
108template<class... T, class... U> bool operator<(const tuple<T...>&, const tuple<U...>&);  // constexpr in C++14
109template<class... T, class... U> bool operator!=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
110template<class... T, class... U> bool operator>(const tuple<T...>&, const tuple<U...>&);  // constexpr in C++14
111template<class... T, class... U> bool operator<=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
112template<class... T, class... U> bool operator>=(const tuple<T...>&, const tuple<U...>&); // constexpr in C++14
113
114template <class... Types, class Alloc>
115  struct uses_allocator<tuple<Types...>, Alloc>;
116
117template <class... Types>
118  void
119  swap(tuple<Types...>& x, tuple<Types...>& y) noexcept(noexcept(x.swap(y)));
120
121}  // std
122
123*/
124
125#include <__config>
126#include <__tuple>
127#include <cstddef>
128#include <type_traits>
129#include <__functional_base>
130#include <utility>
131
132#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
133#pragma GCC system_header
134#endif
135
136_LIBCPP_BEGIN_NAMESPACE_STD
137
138#ifndef _LIBCPP_HAS_NO_VARIADICS
139
140// tuple_size
141
142template <class ..._Tp>
143class _LIBCPP_TYPE_VIS_ONLY tuple_size<tuple<_Tp...> >
144    : public integral_constant<size_t, sizeof...(_Tp)>
145{
146};
147
148// tuple_element
149
150template <size_t _Ip, class ..._Tp>
151class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, tuple<_Tp...> >
152{
153public:
154    typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
155};
156
157#if _LIBCPP_STD_VER > 11
158template <size_t _Ip, class ..._Tp>
159using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type;
160#endif
161
162// __tuple_leaf
163
164template <size_t _Ip, class _Hp, bool=is_empty<_Hp>::value
165#if __has_feature(is_final)
166                                 && !__is_final(_Hp)
167#endif
168         >
169class __tuple_leaf;
170
171template <size_t _Ip, class _Hp, bool _Ep>
172inline _LIBCPP_INLINE_VISIBILITY
173void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y)
174    _NOEXCEPT_(__is_nothrow_swappable<_Hp>::value)
175{
176    swap(__x.get(), __y.get());
177}
178
179template <size_t _Ip, class _Hp, bool>
180class __tuple_leaf
181{
182    _Hp value;
183
184    __tuple_leaf& operator=(const __tuple_leaf&);
185public:
186    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
187             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : value()
188       {static_assert(!is_reference<_Hp>::value,
189              "Attempted to default construct a reference element in a tuple");}
190
191    template <class _Alloc>
192        _LIBCPP_INLINE_VISIBILITY
193        __tuple_leaf(integral_constant<int, 0>, const _Alloc&)
194            : value()
195        {static_assert(!is_reference<_Hp>::value,
196              "Attempted to default construct a reference element in a tuple");}
197
198    template <class _Alloc>
199        _LIBCPP_INLINE_VISIBILITY
200        __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
201            : value(allocator_arg_t(), __a)
202        {static_assert(!is_reference<_Hp>::value,
203              "Attempted to default construct a reference element in a tuple");}
204
205    template <class _Alloc>
206        _LIBCPP_INLINE_VISIBILITY
207        __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
208            : value(__a)
209        {static_assert(!is_reference<_Hp>::value,
210              "Attempted to default construct a reference element in a tuple");}
211
212    template <class _Tp,
213              class = typename enable_if<
214                  __lazy_and<
215                      __lazy_not<is_same<typename decay<_Tp>::type, __tuple_leaf>>
216                    , is_constructible<_Hp, _Tp>
217                    >::value
218                >::type
219            >
220        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
221        explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
222            : value(_VSTD::forward<_Tp>(__t))
223        {static_assert(!is_reference<_Hp>::value ||
224                       (is_lvalue_reference<_Hp>::value &&
225                        (is_lvalue_reference<_Tp>::value ||
226                         is_same<typename remove_reference<_Tp>::type,
227                                 reference_wrapper<
228                                    typename remove_reference<_Hp>::type
229                                 >
230                                >::value)) ||
231                        (is_rvalue_reference<_Hp>::value &&
232                         !is_lvalue_reference<_Tp>::value),
233       "Attempted to construct a reference element in a tuple with an rvalue");}
234
235    template <class _Tp, class _Alloc>
236        _LIBCPP_INLINE_VISIBILITY
237        explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
238            : value(_VSTD::forward<_Tp>(__t))
239        {static_assert(!is_lvalue_reference<_Hp>::value ||
240                       (is_lvalue_reference<_Hp>::value &&
241                        (is_lvalue_reference<_Tp>::value ||
242                         is_same<typename remove_reference<_Tp>::type,
243                                 reference_wrapper<
244                                    typename remove_reference<_Hp>::type
245                                 >
246                                >::value)),
247       "Attempted to construct a reference element in a tuple with an rvalue");}
248
249    template <class _Tp, class _Alloc>
250        _LIBCPP_INLINE_VISIBILITY
251        explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
252            : value(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
253        {static_assert(!is_lvalue_reference<_Hp>::value ||
254                       (is_lvalue_reference<_Hp>::value &&
255                        (is_lvalue_reference<_Tp>::value ||
256                         is_same<typename remove_reference<_Tp>::type,
257                                 reference_wrapper<
258                                    typename remove_reference<_Hp>::type
259                                 >
260                                >::value)),
261       "Attempted to construct a reference element in a tuple with an rvalue");}
262
263    template <class _Tp, class _Alloc>
264        _LIBCPP_INLINE_VISIBILITY
265        explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
266            : value(_VSTD::forward<_Tp>(__t), __a)
267        {static_assert(!is_lvalue_reference<_Hp>::value ||
268                       (is_lvalue_reference<_Hp>::value &&
269                        (is_lvalue_reference<_Tp>::value ||
270                         is_same<typename remove_reference<_Tp>::type,
271                                 reference_wrapper<
272                                    typename remove_reference<_Hp>::type
273                                 >
274                                >::value)),
275       "Attempted to construct a reference element in a tuple with an rvalue");}
276
277    __tuple_leaf(const __tuple_leaf& __t) = default;
278    __tuple_leaf(__tuple_leaf&& __t) = default;
279
280    template <class _Tp>
281        _LIBCPP_INLINE_VISIBILITY
282        __tuple_leaf&
283        operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
284        {
285            value = _VSTD::forward<_Tp>(__t);
286            return *this;
287        }
288
289    _LIBCPP_INLINE_VISIBILITY
290    int swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
291    {
292        _VSTD::swap(*this, __t);
293        return 0;
294    }
295
296    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return value;}
297    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return value;}
298};
299
300template <size_t _Ip, class _Hp>
301class __tuple_leaf<_Ip, _Hp, true>
302    : private _Hp
303{
304
305    __tuple_leaf& operator=(const __tuple_leaf&);
306public:
307    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
308             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) {}
309
310    template <class _Alloc>
311        _LIBCPP_INLINE_VISIBILITY
312        __tuple_leaf(integral_constant<int, 0>, const _Alloc&) {}
313
314    template <class _Alloc>
315        _LIBCPP_INLINE_VISIBILITY
316        __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
317            : _Hp(allocator_arg_t(), __a) {}
318
319    template <class _Alloc>
320        _LIBCPP_INLINE_VISIBILITY
321        __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
322            : _Hp(__a) {}
323
324    template <class _Tp,
325              class = typename enable_if<
326                  __lazy_and<
327                        __lazy_not<is_same<typename decay<_Tp>::type, __tuple_leaf>>
328                      , is_constructible<_Hp, _Tp>
329                    >::value
330                >::type
331            >
332        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
333        explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
334            : _Hp(_VSTD::forward<_Tp>(__t)) {}
335
336    template <class _Tp, class _Alloc>
337        _LIBCPP_INLINE_VISIBILITY
338        explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
339            : _Hp(_VSTD::forward<_Tp>(__t)) {}
340
341    template <class _Tp, class _Alloc>
342        _LIBCPP_INLINE_VISIBILITY
343        explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
344            : _Hp(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t)) {}
345
346    template <class _Tp, class _Alloc>
347        _LIBCPP_INLINE_VISIBILITY
348        explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
349            : _Hp(_VSTD::forward<_Tp>(__t), __a) {}
350
351    __tuple_leaf(__tuple_leaf const &) = default;
352    __tuple_leaf(__tuple_leaf &&) = default;
353
354    template <class _Tp>
355        _LIBCPP_INLINE_VISIBILITY
356        __tuple_leaf&
357        operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
358        {
359            _Hp::operator=(_VSTD::forward<_Tp>(__t));
360            return *this;
361        }
362
363    _LIBCPP_INLINE_VISIBILITY
364    int
365    swap(__tuple_leaf& __t) _NOEXCEPT_(__is_nothrow_swappable<__tuple_leaf>::value)
366    {
367        _VSTD::swap(*this, __t);
368        return 0;
369    }
370
371    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return static_cast<_Hp&>(*this);}
372    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return static_cast<const _Hp&>(*this);}
373};
374
375template <class ..._Tp>
376_LIBCPP_INLINE_VISIBILITY
377void __swallow(_Tp&&...) _NOEXCEPT {}
378
379template <bool ...> struct __all;
380
381template <>
382struct __all<>
383{
384    static const bool value = true;
385};
386
387template <bool _B0, bool ... _Bp>
388struct __all<_B0, _Bp...>
389{
390    static const bool value = _B0 && __all<_Bp...>::value;
391};
392
393// __tuple_impl
394
395template<class _Indx, class ..._Tp> struct __tuple_impl;
396
397template<size_t ..._Indx, class ..._Tp>
398struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
399    : public __tuple_leaf<_Indx, _Tp>...
400{
401    _LIBCPP_INLINE_VISIBILITY
402    _LIBCPP_CONSTEXPR __tuple_impl()
403        _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
404
405    template <size_t ..._Uf, class ..._Tf,
406              size_t ..._Ul, class ..._Tl, class ..._Up>
407        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
408        explicit
409        __tuple_impl(__tuple_indices<_Uf...>, __tuple_types<_Tf...>,
410                     __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
411                     _Up&&... __u)
412                     _NOEXCEPT_((__all<is_nothrow_constructible<_Tf, _Up>::value...>::value &&
413                                 __all<is_nothrow_default_constructible<_Tl>::value...>::value)) :
414            __tuple_leaf<_Uf, _Tf>(_VSTD::forward<_Up>(__u))...,
415            __tuple_leaf<_Ul, _Tl>()...
416            {}
417
418    template <class _Alloc, size_t ..._Uf, class ..._Tf,
419              size_t ..._Ul, class ..._Tl, class ..._Up>
420        _LIBCPP_INLINE_VISIBILITY
421        explicit
422        __tuple_impl(allocator_arg_t, const _Alloc& __a,
423                     __tuple_indices<_Uf...>, __tuple_types<_Tf...>,
424                     __tuple_indices<_Ul...>, __tuple_types<_Tl...>,
425                     _Up&&... __u) :
426            __tuple_leaf<_Uf, _Tf>(__uses_alloc_ctor<_Tf, _Alloc, _Up>(), __a,
427            _VSTD::forward<_Up>(__u))...,
428            __tuple_leaf<_Ul, _Tl>(__uses_alloc_ctor<_Tl, _Alloc>(), __a)...
429            {}
430
431    template <class _Tuple,
432              class = typename enable_if
433                      <
434                         __tuple_constructible<_Tuple, tuple<_Tp...> >::value
435                      >::type
436             >
437        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
438        __tuple_impl(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_constructible<_Tp, typename tuple_element<_Indx,
439                                       typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
440            : __tuple_leaf<_Indx, _Tp>(_VSTD::forward<typename tuple_element<_Indx,
441                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
442            {}
443
444    template <class _Alloc, class _Tuple,
445              class = typename enable_if
446                      <
447                         __tuple_convertible<_Tuple, tuple<_Tp...> >::value
448                      >::type
449             >
450        _LIBCPP_INLINE_VISIBILITY
451        __tuple_impl(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
452            : __tuple_leaf<_Indx, _Tp>(__uses_alloc_ctor<_Tp, _Alloc, typename tuple_element<_Indx,
453                                       typename __make_tuple_types<_Tuple>::type>::type>(), __a,
454                                       _VSTD::forward<typename tuple_element<_Indx,
455                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...
456            {}
457
458    template <class _Tuple>
459        _LIBCPP_INLINE_VISIBILITY
460        typename enable_if
461        <
462            __tuple_assignable<_Tuple, tuple<_Tp...> >::value,
463            __tuple_impl&
464        >::type
465        operator=(_Tuple&& __t) _NOEXCEPT_((__all<is_nothrow_assignable<_Tp&, typename tuple_element<_Indx,
466                                       typename __make_tuple_types<_Tuple>::type>::type>::value...>::value))
467        {
468            __swallow(__tuple_leaf<_Indx, _Tp>::operator=(_VSTD::forward<typename tuple_element<_Indx,
469                                       typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<_Indx>(__t)))...);
470            return *this;
471        }
472
473    __tuple_impl(const __tuple_impl&) = default;
474    __tuple_impl(__tuple_impl&&) = default;
475
476    _LIBCPP_INLINE_VISIBILITY
477    __tuple_impl&
478    operator=(const __tuple_impl& __t) _NOEXCEPT_((__all<is_nothrow_copy_assignable<_Tp>::value...>::value))
479    {
480        __swallow(__tuple_leaf<_Indx, _Tp>::operator=(static_cast<const __tuple_leaf<_Indx, _Tp>&>(__t).get())...);
481        return *this;
482    }
483
484    _LIBCPP_INLINE_VISIBILITY
485    __tuple_impl&
486    operator=(__tuple_impl&& __t) _NOEXCEPT_((__all<is_nothrow_move_assignable<_Tp>::value...>::value))
487    {
488        __swallow(__tuple_leaf<_Indx, _Tp>::operator=(_VSTD::forward<_Tp>(static_cast<__tuple_leaf<_Indx, _Tp>&>(__t).get()))...);
489        return *this;
490    }
491
492    _LIBCPP_INLINE_VISIBILITY
493    void swap(__tuple_impl& __t)
494        _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
495    {
496        __swallow(__tuple_leaf<_Indx, _Tp>::swap(static_cast<__tuple_leaf<_Indx, _Tp>&>(__t))...);
497    }
498};
499
500template <class ..._Tp>
501class _LIBCPP_TYPE_VIS_ONLY tuple
502{
503    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> base;
504
505    base base_;
506
507    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
508        typename tuple_element<_Jp, tuple<_Up...> >::type& get(tuple<_Up...>&) _NOEXCEPT;
509    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
510        const typename tuple_element<_Jp, tuple<_Up...> >::type& get(const tuple<_Up...>&) _NOEXCEPT;
511    template <size_t _Jp, class ..._Up> friend _LIBCPP_CONSTEXPR_AFTER_CXX11
512        typename tuple_element<_Jp, tuple<_Up...> >::type&& get(tuple<_Up...>&&) _NOEXCEPT;
513public:
514
515    _LIBCPP_INLINE_VISIBILITY
516    _LIBCPP_CONSTEXPR tuple()
517        _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
518
519    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
520    explicit tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value))
521        : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
522                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
523                typename __make_tuple_indices<0>::type(),
524                typename __make_tuple_types<tuple, 0>::type(),
525                __t...
526               ) {}
527
528    template <class _Alloc>
529      _LIBCPP_INLINE_VISIBILITY
530      tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
531        : base_(allocator_arg_t(), __a,
532                typename __make_tuple_indices<sizeof...(_Tp)>::type(),
533                typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
534                typename __make_tuple_indices<0>::type(),
535                typename __make_tuple_types<tuple, 0>::type(),
536                __t...
537               ) {}
538
539    template <class ..._Up,
540              typename enable_if
541                      <
542                         sizeof...(_Up) <= sizeof...(_Tp) &&
543                         __tuple_convertible
544                         <
545                            tuple<_Up...>,
546                            typename __make_tuple_types<tuple,
547                                     sizeof...(_Up) < sizeof...(_Tp) ?
548                                        sizeof...(_Up) :
549                                        sizeof...(_Tp)>::type
550                         >::value,
551                         bool
552                      >::type = false
553             >
554        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
555        tuple(_Up&&... __u)
556            _NOEXCEPT_((
557                is_nothrow_constructible<
558                    typename __make_tuple_indices<sizeof...(_Up)>::type,
559                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
560                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
561                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
562                    _Up...
563                >::value
564            ))
565            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
566                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
567                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
568                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
569                    _VSTD::forward<_Up>(__u)...) {}
570
571    template <class ..._Up,
572              typename enable_if
573                      <
574                         sizeof...(_Up) <= sizeof...(_Tp) &&
575                         __tuple_constructible
576                         <
577                            tuple<_Up...>,
578                            typename __make_tuple_types<tuple,
579                                     sizeof...(_Up) < sizeof...(_Tp) ?
580                                        sizeof...(_Up) :
581                                        sizeof...(_Tp)>::type
582                         >::value &&
583                         !__tuple_convertible
584                         <
585                            tuple<_Up...>,
586                            typename __make_tuple_types<tuple,
587                                     sizeof...(_Up) < sizeof...(_Tp) ?
588                                        sizeof...(_Up) :
589                                        sizeof...(_Tp)>::type
590                         >::value,
591                         bool
592                      >::type =false
593             >
594        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
595        explicit
596        tuple(_Up&&... __u)
597            _NOEXCEPT_((
598                is_nothrow_constructible<
599                    typename __make_tuple_indices<sizeof...(_Up)>::type,
600                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
601                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
602                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type,
603                    _Up...
604                >::value
605            ))
606            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
607                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
608                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
609                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
610                    _VSTD::forward<_Up>(__u)...) {}
611
612    template <class _Alloc, class ..._Up,
613              class = typename enable_if
614                      <
615                         sizeof...(_Up) <= sizeof...(_Tp) &&
616                         __tuple_convertible
617                         <
618                            tuple<_Up...>,
619                            typename __make_tuple_types<tuple,
620                                     sizeof...(_Up) < sizeof...(_Tp) ?
621                                        sizeof...(_Up) :
622                                        sizeof...(_Tp)>::type
623                         >::value
624                      >::type
625             >
626        _LIBCPP_INLINE_VISIBILITY
627        tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
628            : base_(allocator_arg_t(), __a,
629                    typename __make_tuple_indices<sizeof...(_Up)>::type(),
630                    typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
631                    typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
632                    typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
633                    _VSTD::forward<_Up>(__u)...) {}
634
635    template <class _Tuple,
636              typename enable_if
637                      <
638                         __tuple_convertible<_Tuple, tuple>::value,
639                         bool
640                      >::type = false
641             >
642        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
643        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
644            : base_(_VSTD::forward<_Tuple>(__t)) {}
645
646    template <class _Tuple,
647              typename enable_if
648                      <
649                         __tuple_constructible<_Tuple, tuple>::value &&
650                         !__tuple_convertible<_Tuple, tuple>::value,
651                         bool
652                      >::type = false
653             >
654        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
655        explicit
656        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
657            : base_(_VSTD::forward<_Tuple>(__t)) {}
658
659    template <class _Alloc, class _Tuple,
660              class = typename enable_if
661                      <
662                         __tuple_convertible<_Tuple, tuple>::value
663                      >::type
664             >
665        _LIBCPP_INLINE_VISIBILITY
666        tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
667            : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
668
669    template <class _Tuple,
670              class = typename enable_if
671                      <
672                         __tuple_assignable<_Tuple, tuple>::value
673                      >::type
674             >
675        _LIBCPP_INLINE_VISIBILITY
676        tuple&
677        operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<base&, _Tuple>::value))
678        {
679            base_.operator=(_VSTD::forward<_Tuple>(__t));
680            return *this;
681        }
682
683    _LIBCPP_INLINE_VISIBILITY
684    void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
685        {base_.swap(__t.base_);}
686};
687
688template <>
689class _LIBCPP_TYPE_VIS_ONLY tuple<>
690{
691public:
692    _LIBCPP_INLINE_VISIBILITY
693    _LIBCPP_CONSTEXPR tuple() _NOEXCEPT {}
694    template <class _Alloc>
695    _LIBCPP_INLINE_VISIBILITY
696        tuple(allocator_arg_t, const _Alloc&) _NOEXCEPT {}
697    template <class _Alloc>
698    _LIBCPP_INLINE_VISIBILITY
699        tuple(allocator_arg_t, const _Alloc&, const tuple&) _NOEXCEPT {}
700    template <class _Up>
701    _LIBCPP_INLINE_VISIBILITY
702        tuple(array<_Up, 0>) _NOEXCEPT {}
703    template <class _Alloc, class _Up>
704    _LIBCPP_INLINE_VISIBILITY
705        tuple(allocator_arg_t, const _Alloc&, array<_Up, 0>) _NOEXCEPT {}
706    _LIBCPP_INLINE_VISIBILITY
707    void swap(tuple&) _NOEXCEPT {}
708};
709
710template <class ..._Tp>
711inline _LIBCPP_INLINE_VISIBILITY
712typename enable_if
713<
714    __all<__is_swappable<_Tp>::value...>::value,
715    void
716>::type
717swap(tuple<_Tp...>& __t, tuple<_Tp...>& __u)
718                 _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
719    {__t.swap(__u);}
720
721// get
722
723template <size_t _Ip, class ..._Tp>
724inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
725typename tuple_element<_Ip, tuple<_Tp...> >::type&
726get(tuple<_Tp...>& __t) _NOEXCEPT
727{
728    typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
729    return static_cast<__tuple_leaf<_Ip, type>&>(__t.base_).get();
730}
731
732template <size_t _Ip, class ..._Tp>
733inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
734const typename tuple_element<_Ip, tuple<_Tp...> >::type&
735get(const tuple<_Tp...>& __t) _NOEXCEPT
736{
737    typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
738    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.base_).get();
739}
740
741template <size_t _Ip, class ..._Tp>
742inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
743typename tuple_element<_Ip, tuple<_Tp...> >::type&&
744get(tuple<_Tp...>&& __t) _NOEXCEPT
745{
746    typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
747    return static_cast<type&&>(
748             static_cast<__tuple_leaf<_Ip, type>&&>(__t.base_).get());
749}
750
751#if _LIBCPP_STD_VER > 11
752// get by type
753template <typename _T1, size_t _Idx, typename... _Args>
754struct __find_exactly_one_t_helper;
755
756// -- find exactly one
757template <typename _T1, size_t _Idx, typename... _Args>
758struct __find_exactly_one_t_checker {
759    static constexpr size_t value = _Idx;
760//  Check the rest of the list to make sure there's only one
761    static_assert ( __find_exactly_one_t_helper<_T1, 0, _Args...>::value == -1, "type can only occur once in type list" );
762    };
763
764
765template <typename _T1, size_t _Idx>
766struct __find_exactly_one_t_helper <_T1, _Idx> {
767    static constexpr size_t value = -1;
768    };
769
770template <typename _T1, size_t _Idx, typename _Head, typename... _Args>
771struct __find_exactly_one_t_helper <_T1, _Idx, _Head, _Args...> {
772    static constexpr size_t value =
773        std::conditional<
774            std::is_same<_T1, _Head>::value,
775            __find_exactly_one_t_checker<_T1, _Idx,   _Args...>,
776            __find_exactly_one_t_helper <_T1, _Idx+1, _Args...>
777        >::type::value;
778    };
779
780template <typename _T1, typename... _Args>
781struct __find_exactly_one_t {
782    static constexpr size_t value = __find_exactly_one_t_helper<_T1, 0, _Args...>::value;
783    static_assert ( value != -1, "type not found in type list" );
784    };
785
786template <class _T1, class... _Args>
787inline _LIBCPP_INLINE_VISIBILITY
788constexpr _T1& get(tuple<_Args...>& __tup) noexcept
789{
790    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);
791}
792
793template <class _T1, class... _Args>
794inline _LIBCPP_INLINE_VISIBILITY
795constexpr _T1 const& get(tuple<_Args...> const& __tup) noexcept
796{
797    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(__tup);
798}
799
800template <class _T1, class... _Args>
801inline _LIBCPP_INLINE_VISIBILITY
802constexpr _T1&& get(tuple<_Args...>&& __tup) noexcept
803{
804    return _VSTD::get<__find_exactly_one_t<_T1, _Args...>::value>(_VSTD::move(__tup));
805}
806
807#endif
808
809// tie
810
811template <class ..._Tp>
812inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
813tuple<_Tp&...>
814tie(_Tp&... __t) _NOEXCEPT
815{
816    return tuple<_Tp&...>(__t...);
817}
818
819template <class _Up>
820struct __ignore_t
821{
822    template <class _Tp>
823        _LIBCPP_INLINE_VISIBILITY
824        const __ignore_t& operator=(_Tp&&) const {return *this;}
825};
826
827namespace { const __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>(); }
828
829template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY reference_wrapper;
830
831template <class _Tp>
832struct __make_tuple_return_impl
833{
834    typedef _Tp type;
835};
836
837template <class _Tp>
838struct __make_tuple_return_impl<reference_wrapper<_Tp> >
839{
840    typedef _Tp& type;
841};
842
843template <class _Tp>
844struct __make_tuple_return
845{
846    typedef typename __make_tuple_return_impl<typename decay<_Tp>::type>::type type;
847};
848
849template <class... _Tp>
850inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
851tuple<typename __make_tuple_return<_Tp>::type...>
852make_tuple(_Tp&&... __t)
853{
854    return tuple<typename __make_tuple_return<_Tp>::type...>(_VSTD::forward<_Tp>(__t)...);
855}
856
857template <class... _Tp>
858inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
859tuple<_Tp&&...>
860forward_as_tuple(_Tp&&... __t) _NOEXCEPT
861{
862    return tuple<_Tp&&...>(_VSTD::forward<_Tp>(__t)...);
863}
864
865template <size_t _Ip>
866struct __tuple_equal
867{
868    template <class _Tp, class _Up>
869    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
870    bool operator()(const _Tp& __x, const _Up& __y)
871    {
872        return __tuple_equal<_Ip - 1>()(__x, __y) && _VSTD::get<_Ip-1>(__x) == _VSTD::get<_Ip-1>(__y);
873    }
874};
875
876template <>
877struct __tuple_equal<0>
878{
879    template <class _Tp, class _Up>
880    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
881    bool operator()(const _Tp&, const _Up&)
882    {
883        return true;
884    }
885};
886
887template <class ..._Tp, class ..._Up>
888inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
889bool
890operator==(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
891{
892    return __tuple_equal<sizeof...(_Tp)>()(__x, __y);
893}
894
895template <class ..._Tp, class ..._Up>
896inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
897bool
898operator!=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
899{
900    return !(__x == __y);
901}
902
903template <size_t _Ip>
904struct __tuple_less
905{
906    template <class _Tp, class _Up>
907    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
908    bool operator()(const _Tp& __x, const _Up& __y)
909    {
910        return __tuple_less<_Ip-1>()(__x, __y) ||
911             (!__tuple_less<_Ip-1>()(__y, __x) && _VSTD::get<_Ip-1>(__x) < _VSTD::get<_Ip-1>(__y));
912    }
913};
914
915template <>
916struct __tuple_less<0>
917{
918    template <class _Tp, class _Up>
919    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
920    bool operator()(const _Tp&, const _Up&)
921    {
922        return false;
923    }
924};
925
926template <class ..._Tp, class ..._Up>
927inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
928bool
929operator<(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
930{
931    return __tuple_less<sizeof...(_Tp)>()(__x, __y);
932}
933
934template <class ..._Tp, class ..._Up>
935inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
936bool
937operator>(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
938{
939    return __y < __x;
940}
941
942template <class ..._Tp, class ..._Up>
943inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
944bool
945operator>=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
946{
947    return !(__x < __y);
948}
949
950template <class ..._Tp, class ..._Up>
951inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
952bool
953operator<=(const tuple<_Tp...>& __x, const tuple<_Up...>& __y)
954{
955    return !(__y < __x);
956}
957
958// tuple_cat
959
960template <class _Tp, class _Up> struct __tuple_cat_type;
961
962template <class ..._Ttypes, class ..._Utypes>
963struct __tuple_cat_type<tuple<_Ttypes...>, __tuple_types<_Utypes...> >
964{
965    typedef tuple<_Ttypes..., _Utypes...> type;
966};
967
968template <class _ResultTuple, bool _Is_Tuple0TupleLike, class ..._Tuples>
969struct __tuple_cat_return_1
970{
971};
972
973template <class ..._Types, class _Tuple0>
974struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0>
975{
976    typedef typename __tuple_cat_type<tuple<_Types...>,
977            typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type>::type
978                                                                           type;
979};
980
981template <class ..._Types, class _Tuple0, class _Tuple1, class ..._Tuples>
982struct __tuple_cat_return_1<tuple<_Types...>, true, _Tuple0, _Tuple1, _Tuples...>
983    : public __tuple_cat_return_1<
984                 typename __tuple_cat_type<
985                     tuple<_Types...>,
986                     typename __make_tuple_types<typename remove_reference<_Tuple0>::type>::type
987                 >::type,
988                 __tuple_like<typename remove_reference<_Tuple1>::type>::value,
989                 _Tuple1, _Tuples...>
990{
991};
992
993template <class ..._Tuples> struct __tuple_cat_return;
994
995template <class _Tuple0, class ..._Tuples>
996struct __tuple_cat_return<_Tuple0, _Tuples...>
997    : public __tuple_cat_return_1<tuple<>,
998         __tuple_like<typename remove_reference<_Tuple0>::type>::value, _Tuple0,
999                                                                     _Tuples...>
1000{
1001};
1002
1003template <>
1004struct __tuple_cat_return<>
1005{
1006    typedef tuple<> type;
1007};
1008
1009inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
1010tuple<>
1011tuple_cat()
1012{
1013    return tuple<>();
1014}
1015
1016template <class _Rp, class _Indices, class _Tuple0, class ..._Tuples>
1017struct __tuple_cat_return_ref_imp;
1018
1019template <class ..._Types, size_t ..._I0, class _Tuple0>
1020struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>, _Tuple0>
1021{
1022    typedef typename remove_reference<_Tuple0>::type _T0;
1023    typedef tuple<_Types..., typename __apply_cv<_Tuple0,
1024                          typename tuple_element<_I0, _T0>::type>::type&&...> type;
1025};
1026
1027template <class ..._Types, size_t ..._I0, class _Tuple0, class _Tuple1, class ..._Tuples>
1028struct __tuple_cat_return_ref_imp<tuple<_Types...>, __tuple_indices<_I0...>,
1029                                  _Tuple0, _Tuple1, _Tuples...>
1030    : public __tuple_cat_return_ref_imp<
1031         tuple<_Types..., typename __apply_cv<_Tuple0,
1032               typename tuple_element<_I0,
1033                  typename remove_reference<_Tuple0>::type>::type>::type&&...>,
1034         typename __make_tuple_indices<tuple_size<typename
1035                                 remove_reference<_Tuple1>::type>::value>::type,
1036         _Tuple1, _Tuples...>
1037{
1038};
1039
1040template <class _Tuple0, class ..._Tuples>
1041struct __tuple_cat_return_ref
1042    : public __tuple_cat_return_ref_imp<tuple<>,
1043               typename __make_tuple_indices<
1044                        tuple_size<typename remove_reference<_Tuple0>::type>::value
1045               >::type, _Tuple0, _Tuples...>
1046{
1047};
1048
1049template <class _Types, class _I0, class _J0>
1050struct __tuple_cat;
1051
1052template <class ..._Types, size_t ..._I0, size_t ..._J0>
1053struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J0...> >
1054{
1055    template <class _Tuple0>
1056    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
1057    typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&>::type
1058    operator()(tuple<_Types...> __t, _Tuple0&& __t0)
1059    {
1060        return forward_as_tuple(_VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
1061                                      _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...);
1062    }
1063
1064    template <class _Tuple0, class _Tuple1, class ..._Tuples>
1065    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
1066    typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&, _Tuple1&&, _Tuples&&...>::type
1067    operator()(tuple<_Types...> __t, _Tuple0&& __t0, _Tuple1&& __t1, _Tuples&& ...__tpls)
1068    {
1069        typedef typename remove_reference<_Tuple0>::type _T0;
1070        typedef typename remove_reference<_Tuple1>::type _T1;
1071        return __tuple_cat<
1072           tuple<_Types..., typename __apply_cv<_Tuple0, typename tuple_element<_J0, _T0>::type>::type&&...>,
1073           typename __make_tuple_indices<sizeof ...(_Types) + tuple_size<_T0>::value>::type,
1074           typename __make_tuple_indices<tuple_size<_T1>::value>::type>()
1075                           (forward_as_tuple(
1076                              _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
1077                              _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...
1078                            ),
1079                            _VSTD::forward<_Tuple1>(__t1),
1080                            _VSTD::forward<_Tuples>(__tpls)...);
1081    }
1082};
1083
1084template <class _Tuple0, class... _Tuples>
1085inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
1086typename __tuple_cat_return<_Tuple0, _Tuples...>::type
1087tuple_cat(_Tuple0&& __t0, _Tuples&&... __tpls)
1088{
1089    typedef typename remove_reference<_Tuple0>::type _T0;
1090    return __tuple_cat<tuple<>, __tuple_indices<>,
1091                  typename __make_tuple_indices<tuple_size<_T0>::value>::type>()
1092                  (tuple<>(), _VSTD::forward<_Tuple0>(__t0),
1093                                            _VSTD::forward<_Tuples>(__tpls)...);
1094}
1095
1096template <class ..._Tp, class _Alloc>
1097struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<tuple<_Tp...>, _Alloc>
1098    : true_type {};
1099
1100template <class _T1, class _T2>
1101template <class... _Args1, class... _Args2, size_t ..._I1, size_t ..._I2>
1102inline _LIBCPP_INLINE_VISIBILITY
1103pair<_T1, _T2>::pair(piecewise_construct_t,
1104                     tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
1105                     __tuple_indices<_I1...>, __tuple_indices<_I2...>)
1106    :  first(_VSTD::forward<_Args1>(_VSTD::get<_I1>( __first_args))...),
1107      second(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
1108{
1109}
1110
1111#endif  // _LIBCPP_HAS_NO_VARIADICS
1112
1113_LIBCPP_END_NAMESPACE_STD
1114
1115#endif  // _LIBCPP_TUPLE
1116