64 lines
3.2 KiB
Markdown
64 lines
3.2 KiB
Markdown
[binary.search]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.8 Sorting and related operations [[alg.sorting]](alg.sorting#binary.search)
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### 26.8.4 Binary search [[alg.binary.search]](alg.binary.search#binary.search)
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#### 26.8.4.5 binary_search [binary.search]
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[ð](#lib:binary_search)
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`template<class ForwardIterator, class T = iterator_traits<ForwardIterator>::value_type>
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constexpr bool
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binary_search(ForwardIterator first, ForwardIterator last,
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const T& value);
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template<class ForwardIterator, class T = iterator_traits<ForwardIterator>::value_type,
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class Compare>
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constexpr bool
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binary_search(ForwardIterator first, ForwardIterator last,
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const T& value, Compare comp);
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template<[forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_iterator [iterator.concept.forward]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I> S, class Proj = identity,
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class T = projected_value_t<I, Proj>,
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[indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<const T*, projected<I, Proj>> Comp = ranges::less>
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constexpr bool ranges::binary_search(I first, S last, const T& value, Comp comp = {},
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Proj proj = {});
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template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
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class T = projected_value_t<iterator_t<R>, Proj>,
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[indirect_strict_weak_order](indirectcallable.indirectinvocable#concept:indirect_strict_weak_order "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<const T*, projected<iterator_t<R>, Proj>> Comp =
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ranges::less>
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constexpr bool ranges::binary_search(R&& r, const T& value, Comp comp = {},
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Proj proj = {});
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9605)
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Let comp be less{} andproj be identity{} for overloads with no parameters by those names[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9610)
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*Preconditions*: The elements e of [first, last)
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are partitioned with respect to the expressionsbool(invoke(comp, invoke(proj, e), value)) and!bool(invoke(comp, value, invoke(proj, e)))[.](#2.sentence-1)
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Also, for all elements e of [first, last),bool(comp(e, value)) implies !bool(comp(value, e)) for the overloads in namespace std[.](#2.sentence-2)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9620)
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*Returns*: true if and only if
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for some iterator i in the range [first, last),!bool(invoke(comp, invoke(proj, *i), value)) &&!bool(invoke(comp, value, invoke(proj, *i))) is true[.](#3.sentence-1)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L9628)
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*Complexity*: At most log2(last - first)+O(1) comparisons and projections[.](#4.sentence-1)
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