[func.search.bmh]

# 22 General utilities library [[utilities]](./#utilities)

## 22.10 Function objects [[function.objects]](function.objects#func.search.bmh)

### 22.10.18 Searchers [[func.search]](func.search#bmh)

#### 22.10.18.4 Class template boyer_moore_horspool_searcher [func.search.bmh]

[ð](#lib:boyer_moore_horspool_searcher)

namespace std {template<class RandomAccessIterator1, class Hash = hash<typename iterator_traits<RandomAccessIterator1>::value_type>, class BinaryPredicate = equal_to<>>class boyer_moore_horspool_searcher {public: boyer_moore_horspool_searcher(RandomAccessIterator1 pat_first,
 RandomAccessIterator1 pat_last,
 Hash hf = Hash(),
 BinaryPredicate pred = BinaryPredicate()); template<class RandomAccessIterator2> pair<RandomAccessIterator2, RandomAccessIterator2>operator()(RandomAccessIterator2 first, RandomAccessIterator2 last) const; private: RandomAccessIterator1 pat_first_; // *exposition only* RandomAccessIterator1 pat_last_; // *exposition only* Hash hash_; // *exposition only* BinaryPredicate pred_; // *exposition only*};}

[ð](#lib:boyer_moore_horspool_searcher,constructor)

`boyer_moore_horspool_searcher(RandomAccessIterator1 pat_first,
                              RandomAccessIterator1 pat_last,
                              Hash hf = Hash(),
                              BinaryPredicate pred = BinaryPredicate());
`

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15501)

*Preconditions*: The value type of RandomAccessIterator1 meets the [*Cpp17DefaultConstructible*](utility.arg.requirements#:Cpp17DefaultConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]"),[*Cpp17CopyConstructible*](utility.arg.requirements#:Cpp17CopyConstructible "16.4.4.2 Template argument requirements [utility.arg.requirements]"), and [*Cpp17CopyAssignable*](utility.arg.requirements#:Cpp17CopyAssignable "16.4.4.2 Template argument requirements [utility.arg.requirements]") requirements[.](#1.sentence-1)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15506)

Let V be iterator_traits<RandomAccessIterator1>​::​value_type[.](#2.sentence-1)

For any two values A and B of type V,
if pred(A, B) == true, then hf(A) == hf(B) is true[.](#2.sentence-2)

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15511)

*Effects*: Initializespat_first_ with pat_first,pat_last_ with pat_last,hash_ with hf, andpred_ with pred[.](#3.sentence-1)

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15520)

*Throws*: Any exception thrown by the copy constructor of RandomAccessIterator1,
or by the default constructor, copy constructor, or the copy assignment operator of the value type of RandomAccessIterator1,
or the copy constructor or operator() of BinaryPredicate or Hash[.](#4.sentence-1)

May throw bad_alloc if additional memory needed for internal data structures cannot be allocated[.](#4.sentence-2)

[ð](#lib:operator(),boyer_moore_horspool_searcher)

`template<class RandomAccessIterator2>
  pair<RandomAccessIterator2, RandomAccessIterator2>
    operator()(RandomAccessIterator2 first, RandomAccessIterator2 last) const;
`

[5](#5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15536)

*Mandates*: RandomAccessIterator1 and RandomAccessIterator2 have the same value type[.](#5.sentence-1)

[6](#6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15541)

*Effects*: Finds a subsequence of equal values in a sequence[.](#6.sentence-1)

[7](#7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15545)

*Returns*: A pair of iterators i and j such that

- [(7.1)](#7.1)

i is the first iterator in the range
[first, last - (pat_last_ - pat_first_)) such that
for every non-negative integer n less than pat_last_ - pat_first_ the following condition holds:pred(*(i + n), *(pat_first_ + n)) != false, and

- [(7.2)](#7.2)

j == next(i, distance(pat_first_, pat_last_))[.](#7.sentence-1)

Returns make_pair(first, first) if [pat_first_, pat_last_) is empty,
otherwise returns make_pair(last, last) if no such iterator is found[.](#7.sentence-2)

[8](#8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/utilities.tex#L15559)

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