xref: /freebsd-src/contrib/llvm-project/libcxx/include/__ranges/to.h (revision 0fca6ea1d4eea4c934cfff25ac9ee8ad6fe95583)
106c3fb27SDimitry Andric // -*- C++ -*-
206c3fb27SDimitry Andric //===----------------------------------------------------------------------===//
306c3fb27SDimitry Andric //
406c3fb27SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
506c3fb27SDimitry Andric // See https://llvm.org/LICENSE.txt for license information.
606c3fb27SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
706c3fb27SDimitry Andric //
806c3fb27SDimitry Andric //===----------------------------------------------------------------------===//
906c3fb27SDimitry Andric 
1006c3fb27SDimitry Andric #ifndef _LIBCPP___RANGES_TO_H
1106c3fb27SDimitry Andric #define _LIBCPP___RANGES_TO_H
1206c3fb27SDimitry Andric 
1306c3fb27SDimitry Andric #include <__algorithm/ranges_copy.h>
1406c3fb27SDimitry Andric #include <__concepts/constructible.h>
1506c3fb27SDimitry Andric #include <__concepts/convertible_to.h>
1606c3fb27SDimitry Andric #include <__concepts/derived_from.h>
1706c3fb27SDimitry Andric #include <__concepts/same_as.h>
1806c3fb27SDimitry Andric #include <__config>
1906c3fb27SDimitry Andric #include <__functional/bind_back.h>
2006c3fb27SDimitry Andric #include <__iterator/back_insert_iterator.h>
2106c3fb27SDimitry Andric #include <__iterator/insert_iterator.h>
2206c3fb27SDimitry Andric #include <__iterator/iterator_traits.h>
2306c3fb27SDimitry Andric #include <__ranges/access.h>
2406c3fb27SDimitry Andric #include <__ranges/concepts.h>
2506c3fb27SDimitry Andric #include <__ranges/from_range.h>
2606c3fb27SDimitry Andric #include <__ranges/range_adaptor.h>
27*0fca6ea1SDimitry Andric #include <__ranges/ref_view.h>
2806c3fb27SDimitry Andric #include <__ranges/size.h>
2906c3fb27SDimitry Andric #include <__ranges/transform_view.h>
3006c3fb27SDimitry Andric #include <__type_traits/add_pointer.h>
3106c3fb27SDimitry Andric #include <__type_traits/is_const.h>
3206c3fb27SDimitry Andric #include <__type_traits/is_volatile.h>
3306c3fb27SDimitry Andric #include <__type_traits/type_identity.h>
3406c3fb27SDimitry Andric #include <__utility/declval.h>
3506c3fb27SDimitry Andric #include <__utility/forward.h>
3606c3fb27SDimitry Andric #include <cstddef>
3706c3fb27SDimitry Andric 
3806c3fb27SDimitry Andric #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
3906c3fb27SDimitry Andric #  pragma GCC system_header
4006c3fb27SDimitry Andric #endif
4106c3fb27SDimitry Andric 
4206c3fb27SDimitry Andric _LIBCPP_BEGIN_NAMESPACE_STD
4306c3fb27SDimitry Andric 
4406c3fb27SDimitry Andric #if _LIBCPP_STD_VER >= 23
4506c3fb27SDimitry Andric 
4606c3fb27SDimitry Andric namespace ranges {
4706c3fb27SDimitry Andric 
4806c3fb27SDimitry Andric template <class _Container>
495f757f3fSDimitry Andric constexpr bool __reservable_container =
505f757f3fSDimitry Andric     sized_range<_Container> && requires(_Container& __c, range_size_t<_Container> __n) {
5106c3fb27SDimitry Andric       __c.reserve(__n);
5206c3fb27SDimitry Andric       { __c.capacity() } -> same_as<decltype(__n)>;
5306c3fb27SDimitry Andric       { __c.max_size() } -> same_as<decltype(__n)>;
5406c3fb27SDimitry Andric     };
5506c3fb27SDimitry Andric 
5606c3fb27SDimitry Andric template <class _Container, class _Ref>
5706c3fb27SDimitry Andric constexpr bool __container_insertable = requires(_Container& __c, _Ref&& __ref) {
5806c3fb27SDimitry Andric   requires(
5906c3fb27SDimitry Andric       requires { __c.push_back(std::forward<_Ref>(__ref)); } ||
6006c3fb27SDimitry Andric       requires { __c.insert(__c.end(), std::forward<_Ref>(__ref)); });
6106c3fb27SDimitry Andric };
6206c3fb27SDimitry Andric 
6306c3fb27SDimitry Andric template <class _Ref, class _Container>
6406c3fb27SDimitry Andric _LIBCPP_HIDE_FROM_ABI constexpr auto __container_inserter(_Container& __c) {
6506c3fb27SDimitry Andric   if constexpr (requires { __c.push_back(std::declval<_Ref>()); }) {
6606c3fb27SDimitry Andric     return std::back_inserter(__c);
6706c3fb27SDimitry Andric   } else {
6806c3fb27SDimitry Andric     return std::inserter(__c, __c.end());
6906c3fb27SDimitry Andric   }
7006c3fb27SDimitry Andric }
7106c3fb27SDimitry Andric 
7206c3fb27SDimitry Andric // Note: making this a concept allows short-circuiting the second condition.
7306c3fb27SDimitry Andric template <class _Container, class _Range>
7406c3fb27SDimitry Andric concept __try_non_recursive_conversion =
7506c3fb27SDimitry Andric     !input_range<_Container> || convertible_to<range_reference_t<_Range>, range_value_t<_Container>>;
7606c3fb27SDimitry Andric 
7706c3fb27SDimitry Andric template <class _Container, class _Range, class... _Args>
7806c3fb27SDimitry Andric concept __constructible_from_iter_pair =
7906c3fb27SDimitry Andric     common_range<_Range> && requires { typename iterator_traits<iterator_t<_Range>>::iterator_category; } &&
8006c3fb27SDimitry Andric     derived_from<typename iterator_traits<iterator_t<_Range>>::iterator_category, input_iterator_tag> &&
8106c3fb27SDimitry Andric     constructible_from<_Container, iterator_t<_Range>, sentinel_t<_Range>, _Args...>;
8206c3fb27SDimitry Andric 
8306c3fb27SDimitry Andric template <class>
8406c3fb27SDimitry Andric concept __always_false = false;
8506c3fb27SDimitry Andric 
8606c3fb27SDimitry Andric // `ranges::to` base template -- the `_Container` type is a simple type template parameter.
8706c3fb27SDimitry Andric template <class _Container, input_range _Range, class... _Args>
8806c3fb27SDimitry Andric   requires(!view<_Container>)
89*0fca6ea1SDimitry Andric [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr _Container to(_Range&& __range, _Args&&... __args) {
9006c3fb27SDimitry Andric   // Mandates: C is a cv-unqualified class type.
9106c3fb27SDimitry Andric   static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
9206c3fb27SDimitry Andric   static_assert(
9306c3fb27SDimitry Andric       !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");
9406c3fb27SDimitry Andric 
9506c3fb27SDimitry Andric   // First see if the non-recursive case applies -- the conversion target is either:
9606c3fb27SDimitry Andric   // - a range with a convertible value type;
9706c3fb27SDimitry Andric   // - a non-range type which might support being created from the input argument(s) (e.g. an `optional`).
9806c3fb27SDimitry Andric   if constexpr (__try_non_recursive_conversion<_Container, _Range>) {
9906c3fb27SDimitry Andric     // Case 1 -- construct directly from the given range.
10006c3fb27SDimitry Andric     if constexpr (constructible_from<_Container, _Range, _Args...>) {
10106c3fb27SDimitry Andric       return _Container(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
10206c3fb27SDimitry Andric     }
10306c3fb27SDimitry Andric 
10406c3fb27SDimitry Andric     // Case 2 -- construct using the `from_range_t` tagged constructor.
10506c3fb27SDimitry Andric     else if constexpr (constructible_from<_Container, from_range_t, _Range, _Args...>) {
10606c3fb27SDimitry Andric       return _Container(from_range, std::forward<_Range>(__range), std::forward<_Args>(__args)...);
10706c3fb27SDimitry Andric     }
10806c3fb27SDimitry Andric 
10906c3fb27SDimitry Andric     // Case 3 -- construct from a begin-end iterator pair.
11006c3fb27SDimitry Andric     else if constexpr (__constructible_from_iter_pair<_Container, _Range, _Args...>) {
11106c3fb27SDimitry Andric       return _Container(ranges::begin(__range), ranges::end(__range), std::forward<_Args>(__args)...);
11206c3fb27SDimitry Andric     }
11306c3fb27SDimitry Andric 
11406c3fb27SDimitry Andric     // Case 4 -- default-construct (or construct from the extra arguments) and insert, reserving the size if possible.
11506c3fb27SDimitry Andric     else if constexpr (constructible_from<_Container, _Args...> &&
11606c3fb27SDimitry Andric                        __container_insertable<_Container, range_reference_t<_Range>>) {
11706c3fb27SDimitry Andric       _Container __result(std::forward<_Args>(__args)...);
11806c3fb27SDimitry Andric       if constexpr (sized_range<_Range> && __reservable_container<_Container>) {
11906c3fb27SDimitry Andric         __result.reserve(static_cast<range_size_t<_Container>>(ranges::size(__range)));
12006c3fb27SDimitry Andric       }
12106c3fb27SDimitry Andric 
12206c3fb27SDimitry Andric       ranges::copy(__range, ranges::__container_inserter<range_reference_t<_Range>>(__result));
12306c3fb27SDimitry Andric 
12406c3fb27SDimitry Andric       return __result;
12506c3fb27SDimitry Andric 
12606c3fb27SDimitry Andric     } else {
12706c3fb27SDimitry Andric       static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
12806c3fb27SDimitry Andric     }
12906c3fb27SDimitry Andric 
13006c3fb27SDimitry Andric     // Try the recursive case.
13106c3fb27SDimitry Andric   } else if constexpr (input_range<range_reference_t<_Range>>) {
13206c3fb27SDimitry Andric     return ranges::to<_Container>(
133*0fca6ea1SDimitry Andric         ref_view(__range) | views::transform([](auto&& __elem) {
13406c3fb27SDimitry Andric           return ranges::to<range_value_t<_Container>>(std::forward<decltype(__elem)>(__elem));
13506c3fb27SDimitry Andric         }),
13606c3fb27SDimitry Andric         std::forward<_Args>(__args)...);
13706c3fb27SDimitry Andric 
13806c3fb27SDimitry Andric   } else {
13906c3fb27SDimitry Andric     static_assert(__always_false<_Container>, "ranges::to: unable to convert to the given container type.");
14006c3fb27SDimitry Andric   }
14106c3fb27SDimitry Andric }
14206c3fb27SDimitry Andric 
14306c3fb27SDimitry Andric template <class _Range>
14406c3fb27SDimitry Andric struct __minimal_input_iterator {
14506c3fb27SDimitry Andric   using iterator_category = input_iterator_tag;
14606c3fb27SDimitry Andric   using value_type        = range_value_t<_Range>;
14706c3fb27SDimitry Andric   using difference_type   = ptrdiff_t;
14806c3fb27SDimitry Andric   using pointer           = add_pointer_t<range_reference_t<_Range>>;
14906c3fb27SDimitry Andric   using reference         = range_reference_t<_Range>;
15006c3fb27SDimitry Andric 
15106c3fb27SDimitry Andric   reference operator*() const;
15206c3fb27SDimitry Andric   pointer operator->() const;
15306c3fb27SDimitry Andric   __minimal_input_iterator& operator++();
15406c3fb27SDimitry Andric   __minimal_input_iterator operator++(int);
15506c3fb27SDimitry Andric   bool operator==(const __minimal_input_iterator&) const;
15606c3fb27SDimitry Andric };
15706c3fb27SDimitry Andric 
15806c3fb27SDimitry Andric // Deduces the full type of the container from the given template template parameter.
15906c3fb27SDimitry Andric template <template <class...> class _Container, input_range _Range, class... _Args>
16006c3fb27SDimitry Andric struct _Deducer {
16106c3fb27SDimitry Andric   _LIBCPP_HIDE_FROM_ABI static constexpr auto __deduce_func() {
16206c3fb27SDimitry Andric     using _InputIter = __minimal_input_iterator<_Range>;
16306c3fb27SDimitry Andric 
16406c3fb27SDimitry Andric     // Case 1 -- can construct directly from the given range.
16506c3fb27SDimitry Andric     if constexpr (requires { _Container(std::declval<_Range>(), std::declval<_Args>()...); }) {
16606c3fb27SDimitry Andric       using _Result = decltype( //
16706c3fb27SDimitry Andric           _Container(std::declval<_Range>(), std::declval<_Args>()...));
16806c3fb27SDimitry Andric       return type_identity<_Result>{};
16906c3fb27SDimitry Andric 
17006c3fb27SDimitry Andric       // Case 2 -- can construct from the given range using the `from_range_t` tagged constructor.
17106c3fb27SDimitry Andric     } else if constexpr ( //
17206c3fb27SDimitry Andric         requires { _Container(from_range, std::declval<_Range>(), std::declval<_Args>()...); }) {
17306c3fb27SDimitry Andric       using _Result = //
17406c3fb27SDimitry Andric           decltype(_Container(from_range, std::declval<_Range>(), std::declval<_Args>()...));
17506c3fb27SDimitry Andric       return type_identity<_Result>{};
17606c3fb27SDimitry Andric 
17706c3fb27SDimitry Andric       // Case 3 -- can construct from a begin-end iterator pair.
17806c3fb27SDimitry Andric     } else if constexpr ( //
17906c3fb27SDimitry Andric         requires { _Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...); }) {
18006c3fb27SDimitry Andric       using _Result =
18106c3fb27SDimitry Andric           decltype(_Container(std::declval<_InputIter>(), std::declval<_InputIter>(), std::declval<_Args>()...));
18206c3fb27SDimitry Andric       return type_identity<_Result>{};
18306c3fb27SDimitry Andric 
18406c3fb27SDimitry Andric     } else {
18506c3fb27SDimitry Andric       static_assert(__always_false<_Range>,
18606c3fb27SDimitry Andric                     "ranges::to: unable to deduce the container type from the template template argument.");
18706c3fb27SDimitry Andric     }
18806c3fb27SDimitry Andric   }
18906c3fb27SDimitry Andric 
19006c3fb27SDimitry Andric   using type = typename decltype(__deduce_func())::type;
19106c3fb27SDimitry Andric };
19206c3fb27SDimitry Andric 
19306c3fb27SDimitry Andric // `ranges::to` specialization -- `_Container` is a template template parameter requiring deduction to figure out the
19406c3fb27SDimitry Andric // container element type.
19506c3fb27SDimitry Andric template <template <class...> class _Container, input_range _Range, class... _Args>
196*0fca6ea1SDimitry Andric [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Range&& __range, _Args&&... __args) {
19706c3fb27SDimitry Andric   using _DeduceExpr = typename _Deducer<_Container, _Range, _Args...>::type;
19806c3fb27SDimitry Andric   return ranges::to<_DeduceExpr>(std::forward<_Range>(__range), std::forward<_Args>(__args)...);
19906c3fb27SDimitry Andric }
20006c3fb27SDimitry Andric 
20106c3fb27SDimitry Andric // Range adaptor closure object 1 -- wrapping the `ranges::to` version where `_Container` is a simple type template
20206c3fb27SDimitry Andric // parameter.
20306c3fb27SDimitry Andric template <class _Container, class... _Args>
20406c3fb27SDimitry Andric   requires(!view<_Container>)
205*0fca6ea1SDimitry Andric [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
20606c3fb27SDimitry Andric   // Mandates: C is a cv-unqualified class type.
20706c3fb27SDimitry Andric   static_assert(!is_const_v<_Container>, "The target container cannot be const-qualified, please remove the const");
20806c3fb27SDimitry Andric   static_assert(
20906c3fb27SDimitry Andric       !is_volatile_v<_Container>, "The target container cannot be volatile-qualified, please remove the volatile");
21006c3fb27SDimitry Andric 
211*0fca6ea1SDimitry Andric   auto __to_func = []<input_range _Range, class... _Tail>(_Range&& __range, _Tail&&... __tail) static
21206c3fb27SDimitry Andric     requires requires { //
21306c3fb27SDimitry Andric       /**/ ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
21406c3fb27SDimitry Andric     }
2155f757f3fSDimitry Andric   { return ranges::to<_Container>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...); };
21606c3fb27SDimitry Andric 
21706c3fb27SDimitry Andric   return __range_adaptor_closure_t(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
21806c3fb27SDimitry Andric }
21906c3fb27SDimitry Andric 
22006c3fb27SDimitry Andric // Range adaptor closure object 2 -- wrapping the `ranges::to` version where `_Container` is a template template
22106c3fb27SDimitry Andric // parameter.
22206c3fb27SDimitry Andric template <template <class...> class _Container, class... _Args>
223*0fca6ea1SDimitry Andric [[nodiscard]] _LIBCPP_HIDE_FROM_ABI constexpr auto to(_Args&&... __args) {
22406c3fb27SDimitry Andric   // clang-format off
22506c3fb27SDimitry Andric   auto __to_func = []<input_range _Range, class... _Tail,
22606c3fb27SDimitry Andric                       class _DeducedExpr = typename _Deducer<_Container, _Range, _Tail...>::type>
227*0fca6ea1SDimitry Andric     (_Range&& __range, _Tail&& ... __tail) static
22806c3fb27SDimitry Andric       requires requires { //
22906c3fb27SDimitry Andric       /**/ ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
23006c3fb27SDimitry Andric     }
23106c3fb27SDimitry Andric   {
23206c3fb27SDimitry Andric     return ranges::to<_DeducedExpr>(std::forward<_Range>(__range), std::forward<_Tail>(__tail)...);
23306c3fb27SDimitry Andric   };
23406c3fb27SDimitry Andric   // clang-format on
23506c3fb27SDimitry Andric 
23606c3fb27SDimitry Andric   return __range_adaptor_closure_t(std::__bind_back(__to_func, std::forward<_Args>(__args)...));
23706c3fb27SDimitry Andric }
23806c3fb27SDimitry Andric 
23906c3fb27SDimitry Andric } // namespace ranges
24006c3fb27SDimitry Andric 
24106c3fb27SDimitry Andric #endif // _LIBCPP_STD_VER >= 23
24206c3fb27SDimitry Andric 
24306c3fb27SDimitry Andric _LIBCPP_END_NAMESPACE_STD
24406c3fb27SDimitry Andric 
24506c3fb27SDimitry Andric #endif // _LIBCPP___RANGES_TO_H
246