std::boyer_moore_searcher

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Defined in header <functional>
template< class RandomIt1,

          class Hash = std::hash<typename std::iterator_traits<RandomIt1>::value_type>,
          class BinaryPredicate = std::equal_to<> >

class boyer_moore_searcher;
 (since C++17)

A searcher suitable for use with the Searcher overload of std::search that implements the Boyer-Moore string searching algorithm.

std::boyer_moore_searcher is CopyConstructible and CopyAssignable.

RandomIt1 must meet the requirements of LegacyRandomAccessIterator.

Member functions

std::boyer_moore_searcher::boyer_moore_searcher

boyer_moore_searcher( RandomIt1 pat_first,

                      RandomIt1 pat_last,
                      Hash hf = Hash(),

                      BinaryPredicate pred = BinaryPredicate() );

Constructs a std::boyer_moore_searcher by storing copies of pat_first, pat_last, hf, and pred, setting up any necessary internal data structures.

The value type of RandomIt1 must be DefaultConstructible, CopyConstructible and CopyAssignable.

For any two values A and B of the type std::iterator_traits<RandomIt1>::value_type, if pred(A, B) == true, then hf(A) == hf(B) shall be true.

Parameters

pat_first, pat_last - a pair of iterators designating the string to be searched for
hf - a callable object used to hash the elements of the string
pred - a callable object used to determine equality

Exceptions

Any exceptions thrown by

  • the copy constructor of RandomIt1;
  • the default constructor, copy constructor, and copy assignment operator of the value type of RandomIt1; or
  • the copy constructor and function call operator of BinaryPredicate or Hash.

May also throw std::bad_alloc if additional memory required for internal data structures cannot be allocated.

std::boyer_moore_searcher::operator()

template< class RandomIt2 >
std::pair<RandomIt2, RandomIt2> operator()( RandomIt2 first, RandomIt2 last ) const;
 (since C++17)

The member function called by the Searcher overload of std::search to perform a search with this searcher. RandomIt2 must meet the requirements of LegacyRandomAccessIterator.

RandomIt1 and RandomIt2 must have the same value type.

Parameters

first, last - a pair of iterators designating the string to be examined

Return value

If the pattern [pat_first, pat_last) is empty, returns std::make_pair(first, first).

Otherwise, returns a pair of iterators to the first and one past last positions in [first, last) where a subsequence that compares equal to [pat_first, pat_last) as defined by pred is located, or std::make_pair(last, last) otherwise.

Notes

Feature-test macro Value Std Comment
__cpp_lib_boyer_moore_searcher 201603L (C++17) searchers

Example

Run this code
#include <algorithm>
#include <functional>
#include <iomanip>
#include <iostream>
#include <string_view>
 
int main()
{
    constexpr std::string_view haystack =
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed "
        "do eiusmod tempor incididunt ut labore et dolore magna aliqua";
 
    const std::string_view needle{"pisci"};
 
    if (const auto it = std::search(haystack.begin(), haystack.end(),
            std::boyer_moore_searcher(needle.begin(), needle.end()));
        it != haystack.end()
    )
        std::cout << "The string " << std::quoted(needle) << " found at offset "
                  << it - haystack.begin() << '\n';
    else
        std::cout << "The string " << std::quoted(needle) << " not found\n";
}

Output: 

The string "pisci" found at offset 43

See also

 searches for a range of elements
(function template)
(C++17)
 standard C++ library search algorithm implementation
(class template)
(C++17)
 Boyer-Moore-Horspool search algorithm implementation
(class template)
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