[alg.nonmodifying]

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

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

### [26.6.1](#alg.all.of) All of [[alg.all.of]](alg.all.of)

[🔗](#lib:all_of)

`template<class InputIterator, class Predicate>
  constexpr bool all_of(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
  bool all_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last,
              Predicate pred);

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr bool ranges::all_of(I first, S last, Pred pred, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr bool ranges::all_of(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  bool ranges::all_of(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  bool ranges::all_of(Ep&& exec, R&& r, Pred pred, Proj proj = {});
`

[1](#alg.all.of-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4408)

Let E be:

- [(1.1)](#alg.all.of-1.1)

pred(*i) for the overloads in namespace std;

- [(1.2)](#alg.all.of-1.2)

invoke(pred, invoke(proj, *i)) for the overloads in namespace ranges[.](#alg.all.of-1.sentence-1)

[2](#alg.all.of-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4418)

*Returns*: false if E is false for some iterator i in the range [first, last), andtrue otherwise[.](#alg.all.of-2.sentence-1)

[3](#alg.all.of-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4424)

*Complexity*: At most last - first applications of the predicate and any projection[.](#alg.all.of-3.sentence-1)

### [26.6.2](#alg.any.of) Any of [[alg.any.of]](alg.any.of)

[🔗](#lib:any_of)

`template<class InputIterator, class Predicate>
  constexpr bool any_of(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
  bool any_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last,
              Predicate pred);

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr bool ranges::any_of(I first, S last, Pred pred, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr bool ranges::any_of(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  bool ranges::any_of(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  bool ranges::any_of(Ep&& exec, R&& r, Pred pred, Proj proj = {});
`

[1](#alg.any.of-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4455)

Let E be:

- [(1.1)](#alg.any.of-1.1)

pred(*i) for the overloads in namespace std;

- [(1.2)](#alg.any.of-1.2)

invoke(pred, invoke(proj, *i)) for the overloads in namespace ranges[.](#alg.any.of-1.sentence-1)

[2](#alg.any.of-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4465)

*Returns*: true if E is true for some iterator i in the range [first, last), and false otherwise[.](#alg.any.of-2.sentence-1)

[3](#alg.any.of-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4470)

*Complexity*: At most last - first applications of the predicate
and any projection[.](#alg.any.of-3.sentence-1)

### [26.6.3](#alg.none.of) None of [[alg.none.of]](alg.none.of)

[🔗](#lib:none_of)

`template<class InputIterator, class Predicate>
  constexpr bool none_of(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
  bool none_of(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last,
               Predicate pred);

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr bool ranges::none_of(I first, S last, Pred pred, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr bool ranges::none_of(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  bool ranges::none_of(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  bool ranges::none_of(Ep&& exec, R&& r, Pred pred, Proj proj = {});
`

[1](#alg.none.of-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4502)

Let E be:

- [(1.1)](#alg.none.of-1.1)

pred(*i) for the overloads in namespace std;

- [(1.2)](#alg.none.of-1.2)

invoke(pred, invoke(proj, *i)) for the overloads in namespace ranges[.](#alg.none.of-1.sentence-1)

[2](#alg.none.of-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4512)

*Returns*: false if E is true for some iterator i in the range [first, last), andtrue otherwise[.](#alg.none.of-2.sentence-1)

[3](#alg.none.of-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4518)

*Complexity*: At most last - first applications of the predicate and any projection[.](#alg.none.of-3.sentence-1)

### [26.6.4](#alg.contains) Contains [[alg.contains]](alg.contains)

[🔗](#lib:contains)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  constexpr bool ranges::contains(I first, S last, const T& value, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
  constexpr bool ranges::contains(R&& r, const T& value, Proj proj = {});
`

[1](#alg.contains-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4537)

*Returns*: ranges​::​find(std​::​move(first), last, value, proj) != last[.](#alg.contains-1.sentence-1)

[🔗](#alg.contains-itemdecl:2)

`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 Proj = identity, class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  bool ranges::contains(Ep&& exec, I first, S last, const T& value, 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 Proj = identity,
         class T = projected_value_t<iterator_t<R>, Proj>>
  requires
    [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
  bool ranges::contains(Ep&& exec, R&& r, const T& value, Proj proj = {});
`

[2](#alg.contains-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4555)

*Returns*: ranges​::​find(std​::​forward<Ep>(exec), first, last, value, proj) != last[.](#alg.contains-2.sentence-1)

[🔗](#lib:contains_subrange)

`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 bool ranges::contains_subrange(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 bool ranges::contains_subrange(R1&& r1, R2&& r2, Pred pred = {},
                                           Proj1 proj1 = {}, Proj2 proj2 = {});
`

[3](#alg.contains-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4576)

*Returns*: first2 == last2 || !ranges::search(first1, last1, first2, last2,
 pred, proj1, proj2).empty()

[🔗](#alg.contains-itemdecl:4)

`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>
  bool ranges::contains_subrange(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>
  bool ranges::contains_subrange(Ep&& exec, R1&& r1, R2&& r2, Pred pred = {},
                                 Proj1 proj1 = {}, Proj2 proj2 = {});
`

[4](#alg.contains-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4599)

*Returns*: first2 == last2 || !ranges::search(std::forward<Ep>(exec), first1, last1,
 first2, last2, pred, proj1, proj2).empty()

### [26.6.5](#alg.foreach) For each [[alg.foreach]](alg.foreach)

[🔗](#lib:for_each)

`template<class InputIterator, class Function>
  constexpr Function for_each(InputIterator first, InputIterator last, Function f);
`

[1](#alg.foreach-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4616)

*Preconditions*: Function meets
the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements (Table [31](utility.arg.requirements#tab:cpp17.moveconstructible "Table 31: Cpp17MoveConstructible requirements"))[.](#alg.foreach-1.sentence-1)

[*Note [1](#alg.foreach-note-1)*:

Function need not meet the requirements of[*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") (Table [32](utility.arg.requirements#tab:cpp17.copyconstructible "Table 32: Cpp17CopyConstructible requirements (in addition to Cpp17MoveConstructible)"))[.](#alg.foreach-1.sentence-2)

— *end note*]

[2](#alg.foreach-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4625)

*Effects*: Applies f to the result of dereferencing
every iterator in the range [first, last),
starting from first and proceeding to last - 1[.](#alg.foreach-2.sentence-1)

[*Note [2](#alg.foreach-note-2)*:

If the type of first meets the requirements of a mutable iterator,f can apply non-constant functions through the dereferenced iterator[.](#alg.foreach-2.sentence-2)

— *end note*]

[3](#alg.foreach-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4635)

*Returns*: f[.](#alg.foreach-3.sentence-1)

[4](#alg.foreach-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4639)

*Complexity*: Applies f exactly last - first times[.](#alg.foreach-4.sentence-1)

[5](#alg.foreach-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4643)

*Remarks*: If f returns a result, the result is ignored[.](#alg.foreach-5.sentence-1)

[🔗](#lib:for_each_)

`template<class ExecutionPolicy, class ForwardIterator, class Function>
  void for_each(ExecutionPolicy&& exec,
                ForwardIterator first, ForwardIterator last,
                Function f);
`

[6](#alg.foreach-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4657)

*Preconditions*: Function meets the [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements[.](#alg.foreach-6.sentence-1)

[7](#alg.foreach-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4661)

*Effects*: Applies f to the result of dereferencing
every iterator in the range [first, last)[.](#alg.foreach-7.sentence-1)

[*Note [3](#alg.foreach-note-3)*:

If the type of first meets the requirements of a mutable iterator,f can apply non-constant functions through the dereferenced iterator[.](#alg.foreach-7.sentence-2)

— *end note*]

[8](#alg.foreach-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4670)

*Complexity*: Applies f exactly last - first times[.](#alg.foreach-8.sentence-1)

[9](#alg.foreach-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4674)

*Remarks*: If f returns a result, the result is ignored[.](#alg.foreach-9.sentence-1)

Implementations do not have
the freedom granted under [[algorithms.parallel.exec]](algorithms.parallel.exec "26.3.3 Effect of execution policies on algorithm execution") to make arbitrary copies of elements from the input sequence[.](#alg.foreach-9.sentence-2)

[10](#alg.foreach-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4681)

[*Note [4](#alg.foreach-note-4)*:

Does not return a copy of its Function parameter,
since parallelization often does not permit efficient state accumulation[.](#alg.foreach-10.sentence-1)

— *end note*]

[🔗](#lib:for_each__)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirectly_unary_invocable](indirectcallable.indirectinvocable#concept:indirectly_unary_invocable "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Fun>
  constexpr ranges::for_each_result<I, Fun>
    ranges::for_each(I first, S last, Fun f, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirectly_unary_invocable](indirectcallable.indirectinvocable#concept:indirectly_unary_invocable "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Fun>
  constexpr ranges::for_each_result<borrowed_iterator_t<R>, Fun>
    ranges::for_each(R&& r, Fun f, Proj proj = {});
`

[11](#alg.foreach-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4701)

*Effects*: Calls invoke(f, invoke(proj, *i)) for every iterator i in the range [first, last),
starting from first and proceeding to last - 1[.](#alg.foreach-11.sentence-1)

[*Note [5](#alg.foreach-note-5)*:

If the result of invoke(proj, *i) is a mutable reference,f can apply non-constant functions[.](#alg.foreach-11.sentence-2)

— *end note*]

[12](#alg.foreach-12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4711)

*Returns*: {last, std​::​move(f)}[.](#alg.foreach-12.sentence-1)

[13](#alg.foreach-13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4715)

*Complexity*: Applies f and proj exactly last - first times[.](#alg.foreach-13.sentence-1)

[14](#alg.foreach-14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4719)

*Remarks*: If f returns a result, the result is ignored[.](#alg.foreach-14.sentence-1)

[15](#alg.foreach-15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4723)

[*Note [6](#alg.foreach-note-6)*:

The overloads in namespace ranges requireFun to model [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")[.](#alg.foreach-15.sentence-1)

— *end note*]

[🔗](#alg.foreach-itemdecl:4)

`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 Proj = identity,
          [indirectly_unary_invocable](indirectcallable.indirectinvocable#concept:indirectly_unary_invocable "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Fun>
  I ranges::for_each(Ep&& exec, I first, S last, Fun f, 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 Proj = identity,
         [indirectly_unary_invocable](indirectcallable.indirectinvocable#concept:indirectly_unary_invocable "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Fun>
  borrowed_iterator_t<R>
    ranges::for_each(Ep&& exec, R&& r, Fun f, Proj proj = {});
`

[16](#alg.foreach-16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4742)

*Effects*: Calls invoke(f, invoke(proj, *i)) for every iterator i in the range [first, last)[.](#alg.foreach-16.sentence-1)

[*Note [7](#alg.foreach-note-7)*:

If the result of invoke(proj, *i) is a mutable reference,f can apply non-constant functions[.](#alg.foreach-16.sentence-2)

— *end note*]

[17](#alg.foreach-17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4752)

*Returns*: last[.](#alg.foreach-17.sentence-1)

[18](#alg.foreach-18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4756)

*Complexity*: Applies f and proj exactly last - first times[.](#alg.foreach-18.sentence-1)

[19](#alg.foreach-19)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4760)

*Remarks*: 

- [(19.1)](#alg.foreach-19.1)

  If f returns a result, the result is ignored[.](#alg.foreach-19.1.sentence-1)

- [(19.2)](#alg.foreach-19.2)

  Implementations do not have the freedom granted under [[algorithms.parallel.exec]](algorithms.parallel.exec "26.3.3 Effect of execution policies on algorithm execution") to make arbitrary copies of elements from the input sequence[.](#alg.foreach-19.2.sentence-1)

- [(19.3)](#alg.foreach-19.3)

  f may modify objects via its arguments ([[algorithms.parallel.user]](algorithms.parallel.user "26.3.2 Requirements on user-provided function objects"))[.](#alg.foreach-19.3.sentence-1)

[*Note [8](#alg.foreach-note-8)*:

Does not return a copy of its Fun parameter,
since parallelization often does not permit
efficient state accumulation[.](#alg.foreach-19.sentence-2)

— *end note*]

[🔗](#lib:for_each_n)

`template<class InputIterator, class Size, class Function>
  constexpr InputIterator for_each_n(InputIterator first, Size n, Function f);
`

[20](#alg.foreach-20)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4785)

*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"))[.](#alg.foreach-20.sentence-1)

[21](#alg.foreach-21)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4790)

*Preconditions*: n >= 0 is true[.](#alg.foreach-21.sentence-1)

Function meets the [*Cpp17MoveConstructible*](utility.arg.requirements#:Cpp17MoveConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements[.](#alg.foreach-21.sentence-2)

[*Note [9](#alg.foreach-note-9)*:

Function need not meet
the requirements of [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]")[.](#alg.foreach-21.sentence-3)

— *end note*]

[22](#alg.foreach-22)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4799)

*Effects*: Applies f to the result of dereferencing
every iterator in the range [first, first + n) in order[.](#alg.foreach-22.sentence-1)

[*Note [10](#alg.foreach-note-10)*:

If the type of first meets the requirements of a mutable iterator,f can apply non-constant functions through the dereferenced iterator[.](#alg.foreach-22.sentence-2)

— *end note*]

[23](#alg.foreach-23)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4808)

*Returns*: first + n[.](#alg.foreach-23.sentence-1)

[24](#alg.foreach-24)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4812)

*Remarks*: If f returns a result, the result is ignored[.](#alg.foreach-24.sentence-1)

[🔗](#lib:for_each_n_)

`template<class ExecutionPolicy, class ForwardIterator, class Size, class Function>
  ForwardIterator for_each_n(ExecutionPolicy&& exec, ForwardIterator first, Size n,
                             Function f);
`

[25](#alg.foreach-25)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4825)

*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"))[.](#alg.foreach-25.sentence-1)

[26](#alg.foreach-26)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4830)

*Preconditions*: n >= 0 is true[.](#alg.foreach-26.sentence-1)

Function meets the [*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements[.](#alg.foreach-26.sentence-2)

[27](#alg.foreach-27)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4835)

*Effects*: Applies f to the result of dereferencing
every iterator in the range [first, first + n)[.](#alg.foreach-27.sentence-1)

[*Note [11](#alg.foreach-note-11)*:

If the type of first meets the requirements of a mutable iterator,f can apply non-constant functions through the dereferenced iterator[.](#alg.foreach-27.sentence-2)

— *end note*]

[28](#alg.foreach-28)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4844)

*Returns*: first + n[.](#alg.foreach-28.sentence-1)

[29](#alg.foreach-29)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4848)

*Remarks*: If f returns a result, the result is ignored[.](#alg.foreach-29.sentence-1)

Implementations do not have
the freedom granted under [[algorithms.parallel.exec]](algorithms.parallel.exec "26.3.3 Effect of execution policies on algorithm execution") to make arbitrary copies of elements from the input sequence[.](#alg.foreach-29.sentence-2)

[🔗](#lib:for_each_n__)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, class Proj = identity,
         [indirectly_unary_invocable](indirectcallable.indirectinvocable#concept:indirectly_unary_invocable "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Fun>
  constexpr ranges::for_each_n_result<I, Fun>
    ranges::for_each_n(I first, iter_difference_t<I> n, Fun f, Proj proj = {});
`

[30](#alg.foreach-30)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4865)

*Preconditions*: n >= 0 is true[.](#alg.foreach-30.sentence-1)

[31](#alg.foreach-31)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4869)

*Effects*: Calls invoke(f, invoke(proj, *i)) for every iterator i in the range
[first, first + n) in order[.](#alg.foreach-31.sentence-1)

[*Note [12](#alg.foreach-note-12)*:

If the result of invoke(proj, *i) is a mutable reference,f can apply non-constant functions[.](#alg.foreach-31.sentence-2)

— *end note*]

[32](#alg.foreach-32)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4879)

*Returns*: {first + n, std​::​move(f)}[.](#alg.foreach-32.sentence-1)

[33](#alg.foreach-33)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4883)

*Remarks*: If f returns a result, the result is ignored[.](#alg.foreach-33.sentence-1)

[34](#alg.foreach-34)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4887)

[*Note [13](#alg.foreach-note-13)*:

The overload in namespace ranges requires Fun to model [copy_constructible](concept.copyconstructible#concept:copy_constructible "18.4.14 Concept copy_­constructible [concept.copyconstructible]")[.](#alg.foreach-34.sentence-1)

— *end note*]

[🔗](#alg.foreach-itemdecl:8)

`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, class Proj = identity,
         [indirectly_unary_invocable](indirectcallable.indirectinvocable#concept:indirectly_unary_invocable "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Fun>
  I ranges::for_each_n(Ep&& exec, I first, iter_difference_t<I> n, Fun f, Proj proj = {});
`

[35](#alg.foreach-35)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4901)

*Preconditions*: n >= 0 is true[.](#alg.foreach-35.sentence-1)

[36](#alg.foreach-36)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4905)

*Effects*: Calls invoke(f, invoke(proj, *i)) for every iterator i in the range [first, first + n)[.](#alg.foreach-36.sentence-1)

[*Note [14](#alg.foreach-note-14)*:

If the result of invoke(proj, *i) is a mutable reference,f can apply non-constant functions[.](#alg.foreach-36.sentence-2)

— *end note*]

[37](#alg.foreach-37)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4915)

*Returns*: first + n[.](#alg.foreach-37.sentence-1)

[38](#alg.foreach-38)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L4919)

*Remarks*: 

- [(38.1)](#alg.foreach-38.1)

  If f returns a result, the result is ignored[.](#alg.foreach-38.1.sentence-1)

- [(38.2)](#alg.foreach-38.2)

  Implementations do not have the freedom granted under [[algorithms.parallel.exec]](algorithms.parallel.exec "26.3.3 Effect of execution policies on algorithm execution") to make arbitrary copies of elements from the input sequence[.](#alg.foreach-38.2.sentence-1)

- [(38.3)](#alg.foreach-38.3)

  f may modify objects via its arguments ([[algorithms.parallel.user]](algorithms.parallel.user "26.3.2 Requirements on user-provided function objects"))[.](#alg.foreach-38.3.sentence-1)

[*Note [15](#alg.foreach-note-15)*:

Does not return a copy of its Fun parameter,
since parallelization often does not permit
efficient state accumulation[.](#alg.foreach-38.sentence-2)

— *end note*]

### [26.6.6](#alg.find) Find [[alg.find]](alg.find)

[🔗](#lib:find)

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

template<class InputIterator, class Predicate>
  constexpr InputIterator find_if(InputIterator first, InputIterator last,
                                  Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
  ForwardIterator find_if(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last,
                          Predicate pred);

template<class InputIterator, class Predicate>
  constexpr InputIterator find_if_not(InputIterator first, InputIterator last,
                                      Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
  ForwardIterator find_if_not(ExecutionPolicy&& exec,
                              ForwardIterator first, ForwardIterator last,
                              Predicate pred);

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  constexpr I ranges::find(I first, S last, const T& value, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
  constexpr borrowed_iterator_t<R>
    ranges::find(R&& r, const T& value, 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 Proj = identity, class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  I ranges::find(Ep&& exec, I first, S last, const T& value, 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 Proj = identity,
         class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to,
                                     projected<iterator_t<R>, Proj>, const T*>
  borrowed_iterator_t<R> ranges::find(Ep&& exec, R&& r, const T& value, Proj proj = {});

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr I ranges::find_if(I first, S last, Pred pred, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr borrowed_iterator_t<R>
    ranges::find_if(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  I ranges::find_if(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  borrowed_iterator_t<R> ranges::find_if(Ep&& exec, R&& r, Pred pred, Proj proj = {});

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr I ranges::find_if_not(I first, S last, Pred pred, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr borrowed_iterator_t<R>
    ranges::find_if_not(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  I ranges::find_if_not(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  borrowed_iterator_t<R> ranges::find_if_not(Ep&& exec, R&& r, Pred pred, Proj proj = {});
`

[1](#alg.find-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5017)

Let E be:

- [(1.1)](#alg.find-1.1)

*i == value for find;

- [(1.2)](#alg.find-1.2)

pred(*i) != false for find_if;

- [(1.3)](#alg.find-1.3)

pred(*i) == false for find_if_not;

- [(1.4)](#alg.find-1.4)

bool(invoke(proj, *i) == value) for ranges​::​find;

- [(1.5)](#alg.find-1.5)

bool(invoke(pred, invoke(proj, *i))) for ranges​::​find_if;

- [(1.6)](#alg.find-1.6)

bool(!invoke(pred, invoke(proj, *i))) for ranges​::​find_if_not[.](#alg.find-1.sentence-1)

[2](#alg.find-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5028)

*Returns*: The first iterator i in the range [first, last)
for which E is true[.](#alg.find-2.sentence-1)

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

[3](#alg.find-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5034)

*Complexity*: At most last - first applications
of the corresponding predicate and any projection[.](#alg.find-3.sentence-1)

### [26.6.7](#alg.find.last) Find last [[alg.find.last]](alg.find.last)

[🔗](#lib:find_last)

`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,
         class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  constexpr subrange<I> ranges::find_last(I first, S last, const T& value, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
  constexpr borrowed_subrange_t<R> ranges::find_last(R&& r, const T& value, 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 Proj = identity, class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  subrange<I> ranges::find_last(Ep&& exec, I first, S last, const T& value, 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 Proj = identity,
          class T = projected_value_t<iterator_t<R>, Proj>>
  requires
    [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
  borrowed_subrange_t<R> ranges::find_last(Ep&& exec, R&& r, const T& value, Proj proj = {});

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,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr subrange<I> ranges::find_last_if(I first, S last, Pred pred, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr borrowed_subrange_t<R> ranges::find_last_if(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  subrange<I> ranges::find_last_if(Ep&& exec, I first, S last, 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 Proj = identity,
          [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  borrowed_subrange_t<R> ranges::find_last_if(Ep&& exec, R&& r, Pred pred, Proj proj = {});

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,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr subrange<I> ranges::find_last_if_not(I first, S last, Pred pred, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr borrowed_subrange_t<R> ranges::find_last_if_not(R&& r, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  subrange<I> ranges::find_last_if_not(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  borrowed_subrange_t<R> ranges::find_last_if_not(Ep&& exec, R&& r, Pred pred, Proj proj = {});
`

[1](#alg.find.last-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5095)

Let E be:

- [(1.1)](#alg.find.last-1.1)

bool(invoke(proj, *i) == value) for ranges​::​find_last;

- [(1.2)](#alg.find.last-1.2)

bool(invoke(pred, invoke(proj, *i))) for ranges​::​find_last_if;

- [(1.3)](#alg.find.last-1.3)

bool(!invoke(pred, invoke(proj, *i))) for ranges​::​find_last_if_not[.](#alg.find.last-1.sentence-1)

[2](#alg.find.last-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5106)

*Returns*: Let i be the last iterator in the range [first, last)
for which E is true[.](#alg.find.last-2.sentence-1)

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

[3](#alg.find.last-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5113)

*Complexity*: At most last - first applications of
the corresponding predicate and projection[.](#alg.find.last-3.sentence-1)

### [26.6.8](#alg.find.end) Find end [[alg.find.end]](alg.find.end)

[🔗](#lib:find_end)

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

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

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::find_end(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::find_end(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::find_end(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::find_end(Ep&& exec, R1&& r1, R2&& r2, Pred pred = {},
                     Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#alg.find.end-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5176)

Let:

- [(1.1)](#alg.find.end-1.1)

pred be equal_to{} for the overloads with no parameter pred;

- [(1.2)](#alg.find.end-1.2)

E be:
  * [(1.2.1)](#alg.find.end-1.2.1)

pred(*(i + n), *(first2 + n)) for the overloads in namespace std;

  * [(1.2.2)](#alg.find.end-1.2.2)

invoke(pred, invoke(proj1, *(i + n)), invoke(proj2, *(first2 + n))) for the overloads in namespace ranges;

- [(1.3)](#alg.find.end-1.3)

i be last1 if [first2, last2) is empty,
 or if (last2 - first2) > (last1 - first1) is true,
 or if there is no iterator
 in the range [first1, last1 - (last2 - first2))
 such that for every non-negative integer n < (last2 - first2), E is true[.](#alg.find.end-1.sentence-1)
  Otherwise i is the last such iterator
 in [first1, last1 - (last2 - first2))[.](#alg.find.end-1.3.sentence-2)

[2](#alg.find.end-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5203)

*Returns*: 

- [(2.1)](#alg.find.end-2.1)

  i for the overloads in namespace std[.](#alg.find.end-2.1.sentence-1)

- [(2.2)](#alg.find.end-2.2)

  {i, i + (i == last1 ? 0 : last2 - first2)} for the overloads in namespace ranges[.](#alg.find.end-2.2.sentence-1)

[3](#alg.find.end-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5211)

*Complexity*: At most(last2 - first2) * (last1 - first1 - (last2 - first2) + 1) applications of the corresponding predicate and any projections[.](#alg.find.end-3.sentence-1)

### [26.6.9](#alg.find.first.of) Find first [[alg.find.first.of]](alg.find.first.of)

[🔗](#lib:find_first_of)

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

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

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,
         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 I1 ranges::find_first_of(I1 first1, S1 last1, I2 first2, S2 last2,
                                     Pred pred = {},
                                     Proj1 proj1 = {}, Proj2 proj2 = {});
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,
         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_iterator_t<R1>
    ranges::find_first_of(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>
  I1 ranges::find_first_of(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_iterator_t<R1>
    ranges::find_first_of(Ep&& exec, R1&& r1, R2&& r2, Pred pred = {},
                          Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#alg.find.first.of-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5275)

Let E be:

- [(1.1)](#alg.find.first.of-1.1)

*i == *j for the overloads with no parameter pred;

- [(1.2)](#alg.find.first.of-1.2)

pred(*i, *j) != false for the overloads with a parameter pred and no parameter proj1;

- [(1.3)](#alg.find.first.of-1.3)

bool(invoke(pred, invoke(proj1, *i), invoke(proj2, *j))) for the overloads with parameters pred and proj1[.](#alg.find.first.of-1.sentence-1)

[2](#alg.find.first.of-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5283)

*Effects*: Finds an element that matches one of a set of values[.](#alg.find.first.of-2.sentence-1)

[3](#alg.find.first.of-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5287)

*Returns*: The first iterator i in the range [first1, last1)
such that for some iterator j in the range [first2, last2)E holds[.](#alg.find.first.of-3.sentence-1)

Returns last1 if [first2, last2) is empty or
if no such iterator is found[.](#alg.find.first.of-3.sentence-2)

[4](#alg.find.first.of-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5296)

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

### [26.6.10](#alg.adjacent.find) Adjacent find [[alg.adjacent.find]](alg.adjacent.find)

[🔗](#lib:adjacent_find)

`template<class ForwardIterator>
  constexpr ForwardIterator
    adjacent_find(ForwardIterator first, ForwardIterator last);
template<class ExecutionPolicy, class ForwardIterator>
  ForwardIterator
    adjacent_find(ExecutionPolicy&& exec,
                  ForwardIterator first, ForwardIterator last);

template<class ForwardIterator, class BinaryPredicate>
  constexpr ForwardIterator
    adjacent_find(ForwardIterator first, ForwardIterator last,
                  BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator, class BinaryPredicate>
  ForwardIterator
    adjacent_find(ExecutionPolicy&& exec,
                  ForwardIterator first, ForwardIterator last,
                  BinaryPredicate pred);

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,
         [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>,
                                   projected<I, Proj>> Pred = ranges::equal_to>
  constexpr I ranges::adjacent_find(I first, S last, Pred pred = {}, Proj proj = {});
template<[forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>,
                                   projected<iterator_t<R>, Proj>> Pred = ranges::equal_to>
  constexpr borrowed_iterator_t<R> ranges::adjacent_find(R&& r, 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 Proj = identity,
         [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>,
                                    projected<I, Proj>> Pred = ranges::equal_to>
  I ranges::adjacent_find(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>,
                                    projected<iterator_t<R>, Proj>> Pred = ranges::equal_to>
  borrowed_iterator_t<R>
    ranges::adjacent_find(Ep&& exec, R&& r, Pred pred = {}, Proj proj = {});
`

[1](#alg.adjacent.find-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5346)

Let E be:

- [(1.1)](#alg.adjacent.find-1.1)

*i == *(i + 1) for the overloads with no parameter pred;

- [(1.2)](#alg.adjacent.find-1.2)

pred(*i, *(i + 1)) != false for the overloads with a parameter pred and no parameter proj;

- [(1.3)](#alg.adjacent.find-1.3)

bool(invoke(pred, invoke(proj, *i), invoke(proj, *(i + 1)))) for the overloads with both parameters pred and proj[.](#alg.adjacent.find-1.sentence-1)

[2](#alg.adjacent.find-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5355)

*Returns*: The first iterator i such that both i and i + 1 are in the range [first, last)
for which E holds[.](#alg.adjacent.find-2.sentence-1)

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

[3](#alg.adjacent.find-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5362)

*Complexity*: For the non-parallel algorithm overloads,
exactly  min((i - first) + 1, (last - first) - 1)  applications of the corresponding predicate,
where i is adjacent_find's return value[.](#alg.adjacent.find-3.sentence-1)

For the parallel algorithm overloads,O(last - first) applications of the corresponding predicate[.](#alg.adjacent.find-3.sentence-2)

No more than twice as many applications of any projection[.](#alg.adjacent.find-3.sentence-3)

### [26.6.11](#alg.count) Count [[alg.count]](alg.count)

[🔗](#lib:count)

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

template<class InputIterator, class Predicate>
  constexpr typename iterator_traits<InputIterator>::difference_type
    count_if(InputIterator first, InputIterator last, Predicate pred);
template<class ExecutionPolicy, class ForwardIterator, class Predicate>
  typename iterator_traits<ForwardIterator>::difference_type
    count_if(ExecutionPolicy&& exec,
             ForwardIterator first, ForwardIterator last, Predicate pred);

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  constexpr iter_difference_t<I>
    ranges::count(I first, S last, const T& value, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity, class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<iterator_t<R>, Proj>, const T*>
  constexpr range_difference_t<R>
    ranges::count(R&& r, const T& value, 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 Proj = identity, class T = projected_value_t<I, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to, projected<I, Proj>, const T*>
  iter_difference_t<I>
    ranges::count(Ep&& exec, I first, S last, const T& value, 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 Proj = identity,
         class T = projected_value_t<iterator_t<R>, Proj>>
  requires [indirect_binary_predicate](indirectcallable.indirectinvocable#concept:indirect_binary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<ranges::equal_to,
                                      projected<iterator_t<R>, Proj>, const T*>
  range_difference_t<R> ranges::count(Ep&& exec, R&& r, const T& value, Proj proj = {});

template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  constexpr iter_difference_t<I>
    ranges::count_if(I first, S last, Pred pred, Proj proj = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  constexpr range_difference_t<R>
    ranges::count_if(R&& r, 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 Proj = identity, [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I, Proj>> Pred>
  iter_difference_t<I>
    ranges::count_if(Ep&& exec, I first, S last, 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 Proj = identity,
         [indirect_unary_predicate](indirectcallable.indirectinvocable#concept:indirect_unary_predicate "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R>, Proj>> Pred>
  range_difference_t<R>
    ranges::count_if(Ep&& exec, R&& r, Pred pred, Proj proj = {});
`

[1](#alg.count-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5436)

Let E be:

- [(1.1)](#alg.count-1.1)

*i == value for the overloads
 with no parameter pred or proj;

- [(1.2)](#alg.count-1.2)

pred(*i) != false for the overloads
 with a parameter pred but no parameter proj;

- [(1.3)](#alg.count-1.3)

invoke(proj, *i) == value for the overloads
 with a parameter proj but no parameter pred;

- [(1.4)](#alg.count-1.4)

bool(invoke(pred, invoke(proj, *i))) for the overloads
 with both parameters proj and pred[.](#alg.count-1.sentence-1)

[2](#alg.count-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5453)

*Effects*: Returns the number of iterators i in the range [first, last)
for which E holds[.](#alg.count-2.sentence-1)

[3](#alg.count-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5458)

*Complexity*: Exactly last - first applications
of the corresponding predicate and any projection[.](#alg.count-3.sentence-1)

### [26.6.12](#alg.mismatch) Mismatch [[alg.mismatch]](alg.mismatch)

[🔗](#lib:mismatch)

`template<class InputIterator1, class InputIterator2>
  constexpr pair<InputIterator1, InputIterator2>
    mismatch(InputIterator1 first1, InputIterator1 last1,
             InputIterator2 first2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
  pair<ForwardIterator1, ForwardIterator2>
    mismatch(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2);

template<class InputIterator1, class InputIterator2,
         class BinaryPredicate>
  constexpr pair<InputIterator1, InputIterator2>
    mismatch(InputIterator1 first1, InputIterator1 last1,
             InputIterator2 first2, BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  pair<ForwardIterator1, ForwardIterator2>
    mismatch(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2, BinaryPredicate pred);

template<class InputIterator1, class InputIterator2>
  constexpr pair<InputIterator1, InputIterator2>
    mismatch(InputIterator1 first1, InputIterator1 last1,
             InputIterator2 first2, InputIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
  pair<ForwardIterator1, ForwardIterator2>
    mismatch(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2, ForwardIterator2 last2);

template<class InputIterator1, class InputIterator2,
         class BinaryPredicate>
  constexpr pair<InputIterator1, InputIterator2>
    mismatch(InputIterator1 first1, InputIterator1 last1,
             InputIterator2 first2, InputIterator2 last2,
             BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  pair<ForwardIterator1, ForwardIterator2>
    mismatch(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2, ForwardIterator2 last2,
             BinaryPredicate pred);

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, [input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") 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 ranges::mismatch_result<I1, I2>
    ranges::mismatch(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
                     Proj1 proj1 = {}, Proj2 proj2 = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [input_range](range.refinements#concept:input_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 ranges::mismatch_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
    ranges::mismatch(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>
  ranges::mismatch_result<I1, I2>
    ranges::mismatch(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>
  ranges::mismatch_result<borrowed_iterator_t<R1>, borrowed_iterator_t<R2>>
    ranges::mismatch(Ep&& exec, R1&& r1, R2&& r2, Pred pred = {},
                     Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#alg.mismatch-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5543)

Let last2 be first2 + (last1 - first1) for the overloads in namespace std with no parameter last2[.](#alg.mismatch-1.sentence-1)

[2](#alg.mismatch-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5547)

Let E be:

- [(2.1)](#alg.mismatch-2.1)

!(*(first1 + n) == *(first2 + n)) for the overloads with no parameter pred;

- [(2.2)](#alg.mismatch-2.2)

pred(*(first1 + n), *(first2 + n)) == false for the overloads with a parameter pred and
 no parameter proj1;

- [(2.3)](#alg.mismatch-2.3)

!invoke(pred, invoke(proj1, *(first1 + n)), invoke(proj2, *(first2 + n))) for the overloads with both parameters pred and proj1[.](#alg.mismatch-2.sentence-1)

[3](#alg.mismatch-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5563)

Let N be min(last1 - first1, last2 - first2)[.](#alg.mismatch-3.sentence-1)

[4](#alg.mismatch-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5566)

*Returns*: { first1 + n, first2 + n },
where n is the smallest integer in [0, N) such that E holds,
or N if no such integer exists[.](#alg.mismatch-4.sentence-1)

[5](#alg.mismatch-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5572)

*Complexity*: At most N applications of the corresponding predicate and any projections[.](#alg.mismatch-5.sentence-1)

### [26.6.13](#alg.equal) Equal [[alg.equal]](alg.equal)

[🔗](#lib:equal)

`template<class InputIterator1, class InputIterator2>
  constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
                       InputIterator2 first2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
  bool equal(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2);

template<class InputIterator1, class InputIterator2,
         class BinaryPredicate>
  constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
                       InputIterator2 first2, BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  bool equal(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2, BinaryPredicate pred);

template<class InputIterator1, class InputIterator2>
  constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
                       InputIterator2 first2, InputIterator2 last2);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2>
  bool equal(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2, ForwardIterator2 last2);

template<class InputIterator1, class InputIterator2,
         class BinaryPredicate>
  constexpr bool equal(InputIterator1 first1, InputIterator1 last1,
                       InputIterator2 first2, InputIterator2 last2,
                       BinaryPredicate pred);
template<class ExecutionPolicy, class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  bool equal(ExecutionPolicy&& exec,
             ForwardIterator1 first1, ForwardIterator1 last1,
             ForwardIterator2 first2, ForwardIterator2 last2,
             BinaryPredicate pred);

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, [input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") 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 bool ranges::equal(I1 first1, S1 last1, I2 first2, S2 last2,
                               Pred pred = {},
                               Proj1 proj1 = {}, Proj2 proj2 = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [input_range](range.refinements#concept:input_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 bool ranges::equal(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>
  bool ranges::equal(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>
  bool ranges::equal(Ep&& exec, R1&& r1, R2&& r2,
                     Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#alg.equal-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5645)

Let:

- [(1.1)](#alg.equal-1.1)

last2 be first2 + (last1 - first1) for the overloads in namespace std with no parameter last2;

- [(1.2)](#alg.equal-1.2)

pred be equal_to{} for the overloads with no parameter pred;

- [(1.3)](#alg.equal-1.3)

E be:
  * [(1.3.1)](#alg.equal-1.3.1)

pred(*i, *(first2 + (i - first1))) for the overloads with no parameter proj1;

  * [(1.3.2)](#alg.equal-1.3.2)

invoke(pred, invoke(proj1, *i), invoke(proj2, *(first2 + (i - first1)))) for the overloads with parameter proj1[.](#alg.equal-1.sentence-1)

[2](#alg.equal-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5667)

*Returns*: If last1 - first1 != last2 - first2, return false[.](#alg.equal-2.sentence-1)

Otherwise return true if E holds for every iterator i in the range [first1, last1)[.](#alg.equal-2.sentence-2)

Otherwise, returns false[.](#alg.equal-2.sentence-3)

[3](#alg.equal-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5674)

*Complexity*: If

- [(3.1)](#alg.equal-3.1)

the types of first1, last1, first2, and last2 meet the [*Cpp17RandomAccessIterator*](random.access.iterators#:Cpp17RandomAccessIterator "24.3.5.7 Random access iterators [random.access.iterators]") requirements ([[random.access.iterators]](random.access.iterators "24.3.5.7 Random access iterators"))
 and last1 - first1 != last2 - first2 for the overloads in namespace std;

- [(3.2)](#alg.equal-3.2)

the types of first1, last1, first2, and last2 pairwise model [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]") ([[iterator.concept.sizedsentinel]](iterator.concept.sizedsentinel "24.3.4.8 Concept sized_­sentinel_­for"))
 and last1 - first1 != last2 - first2 for the first and third overloads in namespace ranges, or

- [(3.3)](#alg.equal-3.3)

R1 and R2 each model [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]") and ranges​::​distance(r1) != ranges​::​distance(r2) for the second and fourth overloads in namespace ranges,

then no applications of the corresponding predicate and each projection;
otherwise, at most min(last1 - first1, last2 - first2)  applications of the corresponding predicate and any projections[.](#alg.equal-3.sentence-1)

### [26.6.14](#alg.is.permutation) Is permutation [[alg.is.permutation]](alg.is.permutation)

[🔗](#lib:is_permutation)

`template<class ForwardIterator1, class ForwardIterator2>
  constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2);
template<class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2, BinaryPredicate pred);
template<class ForwardIterator1, class ForwardIterator2>
  constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2, ForwardIterator2 last2);
template<class ForwardIterator1, class ForwardIterator2,
         class BinaryPredicate>
  constexpr bool is_permutation(ForwardIterator1 first1, ForwardIterator1 last1,
                                ForwardIterator2 first2, ForwardIterator2 last2,
                                BinaryPredicate pred);
`

[1](#alg.is.permutation-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5722)

Let last2 be first2 + (last1 - first1) for the overloads with no parameter named last2,
and let pred be equal_to{} for the overloads with no parameter pred[.](#alg.is.permutation-1.sentence-1)

[2](#alg.is.permutation-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5728)

*Mandates*: ForwardIterator1 and ForwardIterator2 have the same value type[.](#alg.is.permutation-2.sentence-1)

[3](#alg.is.permutation-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5732)

*Preconditions*: The comparison function is an equivalence relation[.](#alg.is.permutation-3.sentence-1)

[4](#alg.is.permutation-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5736)

*Returns*: If last1 - first1 != last2 - first2, return false[.](#alg.is.permutation-4.sentence-1)

Otherwise return true if there exists a permutation of the elements
in the range [first2, last2),
beginning with ForwardIterator2 begin,
such that equal(first1, last1, begin, pred) returns true;
otherwise, returns false[.](#alg.is.permutation-4.sentence-2)

[5](#alg.is.permutation-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5746)

*Complexity*: No applications of the corresponding predicate
if ForwardIterator1 and ForwardIterator2 meet the requirements of random access iterators andlast1 - first1 != last2 - first2[.](#alg.is.permutation-5.sentence-1)

Otherwise, exactly last1 - first1 applications
of the corresponding predicate
if equal(first1, last1, first2, last2, pred) would return true;
otherwise, at worst O(N2), where N has the value last1 - first1[.](#alg.is.permutation-5.sentence-2)

[🔗](#lib:is_permutation_)

`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 Proj1 = identity, class Proj2 = identity,
         [indirect_equivalence_relation](indirectcallable.indirectinvocable#concept:indirect_equivalence_relation "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<I1, Proj1>,
                                       projected<I2, Proj2>> Pred = ranges::equal_to>
  constexpr bool ranges::is_permutation(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 Proj1 = identity, class Proj2 = identity,
         [indirect_equivalence_relation](indirectcallable.indirectinvocable#concept:indirect_equivalence_relation "24.3.6.3 Indirect callables [indirectcallable.indirectinvocable]")<projected<iterator_t<R1>, Proj1>,
                                       projected<iterator_t<R2>, Proj2>> Pred = ranges::equal_to>
  constexpr bool ranges::is_permutation(R1&& r1, R2&& r2, Pred pred = {},
                                        Proj1 proj1 = {}, Proj2 proj2 = {});
`

[6](#alg.is.permutation-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5776)

*Returns*: If last1 - first1 != last2 - first2, return false[.](#alg.is.permutation-6.sentence-1)

Otherwise return true if there exists a permutation of the elements
in the range [first2, last2), bounded by [pfirst, plast),
such thatranges​::​equal(first1, last1, pfirst, plast, pred, proj1, proj2) returns true;
otherwise, returns false[.](#alg.is.permutation-6.sentence-2)

[7](#alg.is.permutation-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L5786)

*Complexity*: No applications of the corresponding predicate and projections if

- [(7.1)](#alg.is.permutation-7.1)

for the first overload,
  * [(7.1.1)](#alg.is.permutation-7.1.1)

S1 and I1 model [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<S1, I1>,

  * [(7.1.2)](#alg.is.permutation-7.1.2)

S2 and I2 model [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<S2, I2>, and

  * [(7.1.3)](#alg.is.permutation-7.1.3)

last1 - first1 != last2 - first2;

- [(7.2)](#alg.is.permutation-7.2)

for the second overload,R1 and R2 each model [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]"), andranges​::​distance(r1) != ranges​::​distance(r2)[.](#alg.is.permutation-7.sentence-1)

Otherwise, exactly last1 - first1 applications
of the corresponding predicate and projections
if ranges​::​equal(​first1, last1, first2, last2, pred, proj1, proj2) would return true;
otherwise, at worst O(N2), where N has the value last1 - first1[.](#alg.is.permutation-7.sentence-2)

### [26.6.15](#alg.search) Search [[alg.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](#alg.search-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[.](#alg.search-1.sentence-1)

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

[2](#alg.search-2)

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

*Complexity*: At most (last1 - first1) * (last2 - first2) applications
of the corresponding predicate[.](#alg.search-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](#alg.search-3)

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

*Returns*: 

- [(3.1)](#alg.search-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)](#alg.search-3.2)

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

[4](#alg.search-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[.](#alg.search-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](#alg.search-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"))[.](#alg.search-5.sentence-1)

[6](#alg.search-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[.](#alg.search-6.sentence-1)

[7](#alg.search-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[.](#alg.search-7.sentence-1)

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

[8](#alg.search-8)

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

*Complexity*: At most last - first applications of the corresponding predicate[.](#alg.search-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](#alg.search-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)[.](#alg.search-9.sentence-1)

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

[10](#alg.search-10)

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

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

[🔗](#lib:search__)

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

[11](#alg.search-11)

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

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

[12](#alg.search-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[.](#alg.search-12.sentence-1)

### [26.6.16](#alg.starts.with) Starts with [[alg.starts.with]](alg.starts.with)

[🔗](#lib:starts_with)

`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, [input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") 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 bool ranges::starts_with(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
                                     Proj1 proj1 = {}, Proj2 proj2 = {});
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [input_range](range.refinements#concept:input_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 bool ranges::starts_with(R1&& r1, R2&& r2, Pred pred = {},
                                     Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#alg.starts.with-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6045)

*Returns*: ranges::mismatch(std::move(first1), last1, std::move(first2), last2,
 pred, proj1, proj2).in2 == last2

[🔗](#alg.starts.with-itemdecl:2)

`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>
  bool ranges::starts_with(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>
  bool ranges::starts_with(Ep&& exec, R1&& r1, R2&& r2,
                           Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
`

[2](#alg.starts.with-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6069)

*Returns*: ranges::mismatch(std::forward<Ep>(exec), std::move(first1), last1, std::move(first2),
 last2, pred, proj1, proj2).in2 == last2

### [26.6.17](#alg.ends.with) Ends with [[alg.ends.with]](alg.ends.with)

[🔗](#lib:ends_with)

`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, [input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") 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 ([forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_­iterator [iterator.concept.forward]")<I1> || [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<S1, I1>) &&
           ([forward_iterator](iterator.concept.forward#concept:forward_iterator "24.3.4.11 Concept forward_­iterator [iterator.concept.forward]")<I2> || [sized_sentinel_for](iterator.concept.sizedsentinel#concept:sized_sentinel_for "24.3.4.8 Concept sized_­sentinel_­for [iterator.concept.sizedsentinel]")<S2, I2>) &&
           [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 bool ranges::ends_with(I1 first1, S1 last1, I2 first2, S2 last2, Pred pred = {},
                                   Proj1 proj1 = {}, Proj2 proj2 = {});
`

[1](#alg.ends.with-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6091)

Let N1 be last1 - first1 andN2 be last2 - first2[.](#alg.ends.with-1.sentence-1)

[2](#alg.ends.with-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6095)

*Returns*: false if N1 < N2, otherwise:ranges::equal(std::move(first1) + (N1 - N2), last1, std::move(first2), last2,
 pred, proj1, proj2)

[🔗](#alg.ends.with-itemdecl:2)

`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>
  bool ranges::ends_with(Ep&& exec, I1 first1, S1 last1, I2 first2, S2 last2,
                         Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
`

[3](#alg.ends.with-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6114)

Let N1 be last1 - first1 andN2 be last2 - first2[.](#alg.ends.with-3.sentence-1)

[4](#alg.ends.with-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6118)

*Returns*: false if N1 < N2, otherwise:ranges::equal(std::forward<Ep>(exec), std::move(first1) + (N1 - N2), last1,
 std::move(first2), last2, pred, proj1, proj2)

[🔗](#alg.ends.with-itemdecl:3)

`template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R1, [input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R2, class Pred = ranges::equal_to, class Proj1 = identity,
         class Proj2 = identity>
  requires ([forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<R1> || [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<R1>) &&
           ([forward_range](range.refinements#concept:forward_range "25.4.6 Other range refinements [range.refinements]")<R2> || [sized_range](range.sized#concept:sized_range "25.4.4 Sized ranges [range.sized]")<R2>) &&
           [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 bool ranges::ends_with(R1&& r1, R2&& r2, Pred pred = {},
                                   Proj1 proj1 = {}, Proj2 proj2 = {});
`

[5](#alg.ends.with-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6138)

Let N1 be ranges​::​distance(r1) andN2 be ranges​::​distance(r2)[.](#alg.ends.with-5.sentence-1)

[6](#alg.ends.with-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6142)

*Returns*: false if N1 < N2, otherwise:ranges::equal(views::drop(ranges::ref_view(r1), N1 - static_cast<decltype(N1)>(N2)),
 r2, pred, proj1, proj2)

[🔗](#alg.ends.with-itemdecl:4)

`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>
  bool ranges::ends_with(Ep&& exec, R1&& r1, R2&& r2,
                         Pred pred = {}, Proj1 proj1 = {}, Proj2 proj2 = {});
`

[7](#alg.ends.with-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6161)

Let N1 be ranges​::​distance(r1) andN2 be ranges​::​distance(r2)[.](#alg.ends.with-7.sentence-1)

[8](#alg.ends.with-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6165)

*Returns*: false if N1 < N2, otherwise:ranges::equal(std::forward<Ep>(exec),
 views::drop(ranges::ref_view(r1), N1 - static_cast<decltype(N1)>(N2)),
 r2, pred, proj1, proj2)

### [26.6.18](#alg.fold) Fold [[alg.fold]](alg.fold)

[🔗](#lib:fold_left)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class T = iter_value_t<I>,
         [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<T, I> F>
  constexpr auto ranges::fold_left(I first, S last, T init, F f);
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class T = range_value_t<R>,
         [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<T, iterator_t<R>> F>
  constexpr auto ranges::fold_left(R&& r, T init, F f);
`

[1](#alg.fold-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6188)

*Returns*: ranges::fold_left_with_iter(std::move(first), last, std::move(init), f).value

[🔗](#lib:fold_left_first)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S,
         [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<iter_value_t<I>, I> F>
  requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<iter_value_t<I>, iter_reference_t<I>>
  constexpr auto ranges::fold_left_first(I first, S last, F f);
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<range_value_t<R>, iterator_t<R>> F>
  requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<range_value_t<R>, range_reference_t<R>>
  constexpr auto ranges::fold_left_first(R&& r, F f);
`

[2](#alg.fold-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6207)

*Returns*: ranges::fold_left_first_with_iter(std::move(first), last, f).value

[🔗](#lib:fold_right)

`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, class T = iter_value_t<I>,
         [indirectly-binary-right-foldable](algorithm.syn#concept:indirectly-binary-right-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<T, I> F>
  constexpr auto ranges::fold_right(I first, S last, T init, F f);
template<[bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]") R, class T = range_value_t<R>,
         [indirectly-binary-right-foldable](algorithm.syn#concept:indirectly-binary-right-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<T, iterator_t<R>> F>
  constexpr auto ranges::fold_right(R&& r, T init, F f);
`

[3](#alg.fold-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6225)

*Effects*: Equivalent to:using U = decay_t<invoke_result_t<F&, iter_reference_t<I>, T>>;if (first == last)return U(std::move(init));
I tail = ranges::next(first, last);
U accum = invoke(f, *--tail, std::move(init));while (first != tail) accum = invoke(f, *--tail, std::move(accum));return accum;

[🔗](#lib:fold_right_last)

`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,
         [indirectly-binary-right-foldable](algorithm.syn#concept:indirectly-binary-right-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<iter_value_t<I>, I> F>
  requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<iter_value_t<I>, iter_reference_t<I>>
  constexpr auto ranges::fold_right_last(I first, S last, F f);
template<[bidirectional_range](range.refinements#concept:bidirectional_range "25.4.6 Other range refinements [range.refinements]") R,
         [indirectly-binary-right-foldable](algorithm.syn#concept:indirectly-binary-right-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<range_value_t<R>, iterator_t<R>> F>
  requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<range_value_t<R>, range_reference_t<R>>
  constexpr auto ranges::fold_right_last(R&& r, F f);
`

[4](#alg.fold-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6253)

Let U bedecltype(ranges​::​fold_right(first, last, iter_value_t<I>(*first), f))[.](#alg.fold-4.sentence-1)

[5](#alg.fold-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6257)

*Effects*: Equivalent to:if (first == last)return optional<U>();
I tail = ranges::prev(ranges::next(first, std::move(last)));return optional<U>(in_place,
 ranges::fold_right(std::move(first), tail, iter_value_t<I>(*tail), std::move(f)));

[🔗](#lib:fold_left_with_iter)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S, class T = iter_value_t<I>,
         [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<T, I> F>
  constexpr see below ranges::fold_left_with_iter(I first, S last, T init, F f);
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, class T = range_value_t<R>,
         [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<T, iterator_t<R>> F>
  constexpr see below ranges::fold_left_with_iter(R&& r, T init, F f);
`

[6](#alg.fold-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6280)

Let U be decay_t<invoke_result_t<F&, T, iter_reference_t<I>>>[.](#alg.fold-6.sentence-1)

[7](#alg.fold-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6283)

*Effects*: Equivalent to:if (first == last)return {std::move(first), U(std::move(init))};
U accum = invoke(f, std::move(init), *first);for (++first; first != last; ++first) accum = invoke(f, std::move(accum), *first);return {std::move(first), std::move(accum)};

[8](#alg.fold-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6295)

*Remarks*: The return type isfold_left_with_iter_result<I, U> for the first overload andfold_left_with_iter_result<borrowed_iterator_t<R>, U> for the second overload[.](#alg.fold-8.sentence-1)

[🔗](#lib:fold_left_first_with_iter)

`template<[input_iterator](iterator.concept.input#concept:input_iterator "24.3.4.9 Concept input_­iterator [iterator.concept.input]") I, [sentinel_for](iterator.concept.sentinel#concept:sentinel_for "24.3.4.7 Concept sentinel_­for [iterator.concept.sentinel]")<I> S,
         [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<iter_value_t<I>, I> F>
  requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<iter_value_t<I>, iter_reference_t<I>>
  constexpr see below ranges::fold_left_first_with_iter(I first, S last, F f);
template<[input_range](range.refinements#concept:input_range "25.4.6 Other range refinements [range.refinements]") R, [indirectly-binary-left-foldable](algorithm.syn#concept:indirectly-binary-left-foldable "26.4 Header <algorithm> synopsis [algorithm.syn]")<range_value_t<R>, iterator_t<R>> F>
  requires [constructible_from](concept.constructible#concept:constructible_from "18.4.11 Concept constructible_­from [concept.constructible]")<range_value_t<R>, range_reference_t<R>>
  constexpr see below ranges::fold_left_first_with_iter(R&& r, F f);
`

[9](#alg.fold-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6315)

Let U bedecltype(ranges::fold_left(std::move(first), last, iter_value_t<I>(*first), f))

[10](#alg.fold-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6321)

*Effects*: Equivalent to:if (first == last)return {std::move(first), optional<U>()};
optional<U> init(in_place, *first);for (++first; first != last; ++first)*init = invoke(f, std::move(*init), *first);return {std::move(first), std::move(init)};

[11](#alg.fold-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/algorithms.tex#L6333)

*Remarks*: The return type isfold_left_first_with_iter_result<I, optional<U>> for the first overload andfold_left_first_with_iter_result<borrowed_iterator_t<R>, optional<U>> for the second overload[.](#alg.fold-11.sentence-1)