[alg.search]

# 26 Algorithms library [[algorithms]](./#algorithms)

## 26.6 Non-modifying sequence operations [[alg.nonmodifying]](alg.nonmodifying#alg.search)

### 26.6.15 Search [alg.search]

[🔗](#lib:search)

`template<class ForwardIterator1, class ForwardIterator2>
  constexpr ForwardIterator1
    search(ForwardIterator1 first1, ForwardIterator1 last1,
           ForwardIterator2 first2, ForwardIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
  ForwardIterator1
    search(ExecutionPolicy&& exec,
           ForwardIterator1 first1, ForwardIterator1 last1,
           ForwardIterator2 first2, ForwardIterator2 last2);

template<class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  constexpr ForwardIterator1
    search(ForwardIterator1 first1, ForwardIterator1 last1,
           ForwardIterator2 first2, ForwardIterator2 last2,
           BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  ForwardIterator1
    search(ExecutionPolicy&& exec,
           ForwardIterator1 first1, ForwardIterator1 last1,
           ForwardIterator2 first2, ForwardIterator2 last2,
           BinaryPredicate pred);
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5839)

*Returns*: The first iterator i in the range [first1, last1 - (last2 - first2)]
such that
for every non-negative integer n less than last2 - first2 the following corresponding conditions hold:*(i + n) == *(first2 + n), pred(*(i + n), *(first2 + n)) != false[.](#1.sentence-1)

Returns first1 if [first2, last2) is empty,
otherwise returns last1 if no such iterator is found[.](#1.sentence-2)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5849)

*Complexity*: At most (last1 - first1) * (last2 - first2) applications
of the corresponding predicate[.](#2.sentence-1)

[🔗](#lib:search_)

`template<[forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_­iterator [iterator.concept.forward]") 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, class Pred = ranges::equal_to,
         class Proj1 = identity, class Proj2 = identity>
  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>
  constexpr subrange<I1>
    ranges::search(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
                   Proj1 proj1 = {}, Proj2 proj2 = {});
template<[forward_range](range.refinements#concept:forward_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, class Pred = ranges::equal_to,
         class Proj1 = identity, class Proj2 = identity>
  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>
  constexpr borrowed_subrange_t<R1>
    ranges::search(R1&& r1, R2&& r2, Pred pred = {},
                   Proj1 proj1 = {}, Proj2 proj2 = {});

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,
         [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,
         class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
  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>
  subrange<I1>
    ranges::search(Ep&& exec, I1 first1, S1 last1, I2 first2, S2 last2,
                   Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
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,
         class Pred = ranges::equal_to, class Proj1 = identity, class Proj2 = identity>
  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>
  borrowed_subrange_t<R1>
    ranges::search(Ep&& exec, R1&& r1, R2&& r2,
                   Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5887)

*Returns*: 

- [(3.1)](#3.1)

{i, i + (last2 - first2)},
 where i is
 the first iterator in the range [first1, last1 - (last2 - first2)]
 such that
 for every non-negative integer n less than last2 - first2 the conditionbool(invoke(pred, invoke(proj1, *(i + n)), invoke(proj2, *(first2 + n)))) is true.

- [(3.2)](#3.2)

Returns {last1, last1} if no such iterator exists.

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5905)

*Complexity*: At most (last1 - first1) * (last2 - first2) applications
of the corresponding predicate and projections[.](#4.sentence-1)

[🔗](#lib:search_n)

`template<class ForwardIterator, class Size, class T = iterator_traits<ForwardIterator>::value_type>
  constexpr ForwardIterator
    search_n(ForwardIterator first, ForwardIterator last,
             Size count, const T& value);
template<class ExecutionPolicy, class ForwardIterator, class Size,
         class T = iterator_traits<ForwardIterator>::value_type>
  ForwardIterator
    search_n(ExecutionPolicy&& exec,
             ForwardIterator first, ForwardIterator last,
             Size count, const T& value);

template<class ForwardIterator, class Size, class T = iterator_traits<ForwardIterator>::value_type,
         class BinaryPredicate>
  constexpr ForwardIterator
    search_n(ForwardIterator first, ForwardIterator last,
             Size count, const T& value,
             BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Size,
         class T = iterator_traits<ForwardIterator>::value_type,
         class BinaryPredicate>
  ForwardIterator
    search_n(ExecutionPolicy&& exec,
             ForwardIterator first, ForwardIterator last,
             Size count, const T& value,
             BinaryPredicate pred);
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5942)

*Mandates*: The type Size is convertible to an integral type ([[conv.integral]](conv.integral "7.3.9 Integral conversions"), [[class.conv]](class.conv "11.4.8 Conversions"))[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5947)

Let E be pred(*(i + n), value) != false for the overloads with a parameter pred,
and *(i + n) == value otherwise[.](#6.sentence-1)

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5952)

*Returns*: The first iterator i in the range [first, last - count]
such that for every non-negative integer n less than count the condition E is true[.](#7.sentence-1)

Returns last if no such iterator is found[.](#7.sentence-2)

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5959)

*Complexity*: At most last - first applications of the corresponding predicate[.](#8.sentence-1)

[🔗](#lib:search_n_)

`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 Pred = ranges::equal_to, class Proj = identity,
         class T = projected_value_t<I, Proj>>
  requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_­comparable [alg.req.ind.cmp]")<I, const T*, Pred, Proj>
  constexpr subrange<I>
    ranges::search_n(I first, S last, iter_difference_t<I> count,
                     const T& value, Pred pred = {}, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Pred = ranges::equal_to,
         class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_­comparable [alg.req.ind.cmp]")<iterator_t<R>, const T*, Pred, Proj>
  constexpr borrowed_subrange_t<R>
    ranges::search_n(R&& r, range_difference_t<R> count,
                     const T& value, Pred pred = {}, Proj proj = {});

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,
         class Pred = ranges::equal_to, class Proj = identity,
         class T = projected_value_t<I, Proj>>
  requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_­comparable [alg.req.ind.cmp]")<I, const T*, Pred, Proj>
  subrange<I>
    ranges::search_n(Ep&& exec, I first, S last, iter_difference_t<I> count,
                     const T& value, Pred pred = {}, Proj proj = {});
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, class Pred = ranges::equal_to,
         class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirectly_comparable](alg.req.ind.cmp#concept:indirectly_comparable "24.3.7.5 Concept indirectly_­comparable [alg.req.ind.cmp]")<iterator_t<R>, const T*, Pred, Proj>
  borrowed_subrange_t<R>
    ranges::search_n(Ep&& exec, R&& r, range_difference_t<R> count,
                     const T& value, Pred pred = {}, Proj proj = {});
`

[9](#9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5996)

*Returns*: {i, i + count} where i is the first iterator in the range [first, last - count]
such that for every non-negative integer n less than count,
the following condition holds:invoke(pred, invoke(proj, *(i + n)), value)[.](#9.sentence-1)

Returns {last, last} if no such iterator is found[.](#9.sentence-2)

[10](#10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6005)

*Complexity*: At most last - first applications
of the corresponding predicate and projection[.](#10.sentence-1)

[🔗](#lib:search__)

`template<class ForwardIterator, class Searcher>
  constexpr ForwardIterator
    search(ForwardIterator first, ForwardIterator last, const Searcher& searcher);
`

[11](#11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6019)

*Effects*: Equivalent to: return searcher(first, last).first;

[12](#12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6023)

*Remarks*: Searcher need not meet the [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements[.](#12.sentence-1)