168 lines
9.4 KiB
Markdown
168 lines
9.4 KiB
Markdown
[alg.reverse]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.7 Mutating sequence operations [[alg.modifying.operations]](alg.modifying.operations#alg.reverse)
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### 26.7.10 Reverse [alg.reverse]
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[ð](#lib:reverse)
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`template<class BidirectionalIterator>
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constexpr void reverse(BidirectionalIterator first, BidirectionalIterator last);
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template<class ExecutionPolicy, class BidirectionalIterator>
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void reverse(ExecutionPolicy&& exec,
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BidirectionalIterator first, BidirectionalIterator last);
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template<[bidirectional_iterator](iterator.concept.bidir#concept:bidirectional_iterator "24.3.4.12 Concept bidirectional_iterator [iterator.concept.bidir]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I> S>
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requires [permutable](alg.req.permutable#concept:permutable "24.3.7.6 Concept permutable [alg.req.permutable]")<I>
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constexpr I ranges::reverse(I first, S last);
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template<[bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]") R>
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requires [permutable](alg.req.permutable#concept:permutable "24.3.7.6 Concept permutable [alg.req.permutable]")<iterator_t<R>>
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constexpr borrowed_iterator_t<R> ranges::reverse(R&& r);
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template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_access_iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<I> S>
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requires [permutable](alg.req.permutable#concept:permutable "24.3.7.6 Concept permutable [alg.req.permutable]")<I>
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I ranges::reverse(Ep&& exec, I first, S last);
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template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R>
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requires [permutable](alg.req.permutable#concept:permutable "24.3.7.6 Concept permutable [alg.req.permutable]")<iterator_t<R>>
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borrowed_iterator_t<R> ranges::reverse(Ep&& exec, R&& r);
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8064)
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*Preconditions*: For the overloads in namespace std,BidirectionalIterator meets
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the [*Cpp17ValueSwappable*](swappable.requirements#:Cpp17ValueSwappable "16.4.4.3 Swappable requirements [swappable.requirements]") requirements ([[swappable.requirements]](swappable.requirements "16.4.4.3 Swappable requirements"))[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8070)
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*Effects*: For each non-negative integer i < (last - first) / 2,
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applies std::iter_swap, orranges::iter_swap for the overloads in namespace ranges,
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to all pairs of iterators first + i, (last - i) - 1[.](#2.sentence-1)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8077)
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*Returns*: last for the overloads in namespace ranges[.](#3.sentence-1)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8081)
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*Complexity*: Exactly (last - first)/2 swaps[.](#4.sentence-1)
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[ð](#lib:reverse_copy)
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`template<class BidirectionalIterator, class OutputIterator>
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constexpr OutputIterator
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reverse_copy(BidirectionalIterator first, BidirectionalIterator last,
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OutputIterator result);
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template<class ExecutionPolicy, class BidirectionalIterator, class ForwardIterator>
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ForwardIterator
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reverse_copy(ExecutionPolicy&& exec,
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BidirectionalIterator first, BidirectionalIterator last,
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ForwardIterator result);
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template<[bidirectional_iterator](iterator.concept.bidir#concept:bidirectional_iterator "24.3.4.12 Concept bidirectional_iterator [iterator.concept.bidir]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I> S, [weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_incrementable [iterator.concept.winc]") O>
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requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_copyable [alg.req.ind.copy]")<I, O>
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constexpr ranges::reverse_copy_result<I, O>
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ranges::reverse_copy(I first, S last, O result);
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template<[bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]") R, [weakly_incrementable](iterator.concept.winc#concept:weakly_incrementable "24.3.4.4 Concept weakly_incrementable [iterator.concept.winc]") O>
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requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_copyable [alg.req.ind.copy]")<iterator_t<R>, O>
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constexpr ranges::reverse_copy_result<borrowed_iterator_t<R>, O>
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ranges::reverse_copy(R&& r, O result);
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`
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[5](#5)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8109)
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Let N be last - first[.](#5.sentence-1)
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[6](#6)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8112)
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*Preconditions*: The ranges [first, last) and [result, result + N)
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do not overlap[.](#6.sentence-1)
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[7](#7)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8117)
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*Effects*: Copies the range [first, last) to the range [result, result + N)
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such that for every non-negative integer i < N the following assignment takes place:*(result + N - 1 - i) = *(first + i)[.](#7.sentence-1)
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[8](#8)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8124)
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*Returns*:
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- [(8.1)](#8.1)
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result + N for the overloads in namespace std[.](#8.1.sentence-1)
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- [(8.2)](#8.2)
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{last, result + N} for the overloads in namespace ranges[.](#8.2.sentence-1)
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[9](#9)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8133)
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*Complexity*: Exactly N assignments[.](#9.sentence-1)
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[ð](#itemdecl:3)
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`template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_access_iterator [iterator.concept.random.access]") I, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<I> S,
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[random_access_iterator](iterator.concept.random.access#concept:random_access_iterator "24.3.4.13 Concept random_access_iterator [iterator.concept.random.access]") O, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<O> OutS>
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requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_copyable [alg.req.ind.copy]")<I, O>
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ranges::reverse_copy_truncated_result<I, O>
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ranges::reverse_copy(Ep&& exec, I first, S last, O result,
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OutS result_last);
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template<[execution-policy](algorithms.parallel.defns#concept:execution-policy "26.3.1 Preamble [algorithms.parallel.defns]") Ep, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") OutR>
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requires [indirectly_copyable](alg.req.ind.copy#concept:indirectly_copyable "24.3.7.3 Concept indirectly_copyable [alg.req.ind.copy]")<iterator_t<R>, iterator_t<OutR>>
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ranges::reverse_copy_truncated_result<borrowed_iterator_t<R>, borrowed_iterator_t<OutR>>
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ranges::reverse_copy(Ep&& exec, R&& r, OutR&& result_r);
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`
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[10](#10)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8152)
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Let N be min(last - first, result_last - result),
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and let *NEW_FIRST* be first + (last - first) - N[.](#10.sentence-1)
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[11](#11)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8156)
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*Preconditions*: The ranges [first, last) and [result, result + N)
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do not overlap[.](#11.sentence-1)
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[12](#12)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8161)
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*Effects*: Copies the range [*NEW_FIRST*, last)
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to the range [result, result + N)
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such that for every non-negative integer i<N the following assignment takes place:*(result + N - 1 - i) = *(*NEW_FIRST* + i)[.](#12.sentence-1)
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[13](#13)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8169)
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*Returns*: {last, *NEW_FIRST*, result + N}[.](#13.sentence-1)
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[14](#14)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L8173)
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*Complexity*: Exactly N assignments[.](#14.sentence-1)
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