103 lines
6.3 KiB
Markdown
103 lines
6.3 KiB
Markdown
[alg.find.first.of]
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# 26 Algorithms library [[algorithms]](./#algorithms)
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## 26.6 Non-modifying sequence operations [[alg.nonmodifying]](alg.nonmodifying#alg.find.first.of)
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### 26.6.9 Find first [alg.find.first.of]
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[ð](#lib:find_first_of)
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`template<class InputIterator, class ForwardIterator>
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constexpr InputIterator
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find_first_of(InputIterator first1, InputIterator last1,
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ForwardIterator first2, ForwardIterator last2);
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template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
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ForwardIterator1
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find_first_of(ExecutionPolicy&& exec,
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ForwardIterator1 first1, ForwardIterator1 last1,
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ForwardIterator2 first2, ForwardIterator2 last2);
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template<class InputIterator, class ForwardIterator,
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class BinaryPredicate>
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constexpr InputIterator
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find_first_of(InputIterator first1, InputIterator last1,
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ForwardIterator first2, ForwardIterator last2,
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BinaryPredicate pred);
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template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
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class BinaryPredicate>
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ForwardIterator1
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find_first_of(ExecutionPolicy&& exec,
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ForwardIterator1 first1, ForwardIterator1 last1,
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ForwardIterator2 first2, ForwardIterator2 last2,
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BinaryPredicate pred);
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template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_iterator [iterator.concept.input]") I1, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I1> S1, [forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_iterator [iterator.concept.forward]") I2, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_for [iterator.concept.sentinel]")<I2> S2,
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class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
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requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_comparable [alg.req.ind.cmp]")<I1, I2, Pred, Proj1, Proj2>
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constexpr I1 ranges::find_first_of(I1 first1, S1 last1, I2 first2, S2 last2,
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Pred pred = {},
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Proj1 proj1 = {}, Proj2 proj2 = {});
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template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R2,
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class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
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requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_comparable [alg.req.ind.cmp]")<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
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constexpr borrowed_iterator_t<R1>
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ranges::find_first_of(R1&& r1, R2&& r2,
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Pred pred = {},
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Proj1 proj1 = {}, Proj2 proj2 = {});
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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]") I1, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<I1> S1,
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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]") I2, [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_sentinel_for [iterator.concept.sizedsentinel]")<I2> S2,
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class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
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requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_comparable [alg.req.ind.cmp]")<I1, I2, Pred, Proj1, Proj2>
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I1 ranges::find_first_of(Ep&& exec, I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
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Proj1 proj1 = {}, Proj2 proj2 = {});
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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]") R1, [sized-random-access-range](range.refinements#concept:sized-random-access-range "25.4.6 Other range refinements [range.refinements]") R2,
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class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
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requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_comparable [alg.req.ind.cmp]")<iterator_t<R1>, iterator_t<R2>, Pred, Proj1, Proj2>
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borrowed_iterator_t<R1>
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ranges::find_first_of(Ep&& exec, R1&& r1, R2&& r2, Pred pred = {},
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Proj1 proj1 = {}, Proj2 proj2 = {});
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`
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[1](#1)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5275)
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Let E be:
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- [(1.1)](#1.1)
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*i == *j for the overloads with no parameter pred;
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- [(1.2)](#1.2)
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pred(*i, *j) != false for the overloads with a parameter pred and no parameter proj1;
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- [(1.3)](#1.3)
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bool(invoke(pred, invoke(proj1, *i), invoke(proj2, *j))) for the overloads with parameters pred and proj1[.](#1.sentence-1)
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[2](#2)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5283)
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*Effects*: Finds an element that matches one of a set of values[.](#2.sentence-1)
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[3](#3)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5287)
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*Returns*: The first iterator i in the range [first1, last1)
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such that for some iterator j in the range [first2, last2)E holds[.](#3.sentence-1)
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Returns last1 if [first2, last2) is empty or
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if no such iterator is found[.](#3.sentence-2)
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[4](#4)
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[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5296)
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*Complexity*: At most (last1 - first1) * (last2 - first2) applications
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of the corresponding predicate and any projections[.](#4.sentence-1)
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