std:: boyer_moore_horspool_searcher

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boyer_moore_horspool_searcher
(C++17)
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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_horspool_searcher ;
(since C++17)

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

std::boyer_moore_horspool_searcher is CopyConstructible and CopyAssignable .

RandomIt1 must meet the requirements of LegacyRandomAccessIterator .

Member functions

std::boyer_moore_horspool_searcher:: boyer_moore_horspool_searcher

boyer_moore_horspool_searcher ( RandomIt1 pat_first,

RandomIt1 pat_last,
Hash hf = Hash ( ) ,

BinaryPredicate pred = BinaryPredicate ( ) ) ;

Constructs a std::boyer_moore_horspool_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, or copy assignment operator of the value type of RandomIt1 ; or
  • the copy constructor or 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_horspool_searcher:: operator()

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

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 Feature
__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 in =
        "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"};
 
    auto it = std::search(in.begin(), in.end(),
                  std::boyer_moore_horspool_searcher(
                      needle.begin(), needle.end()));
    if (it != in.end())
        std::cout << "The string " << std::quoted(needle) << " found at offset "
                  << it - in.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 the first occurrence of a range of elements
(function template)
(C++17)
standard C++ library search algorithm implementation
(class template)
(C++17)
Boyer-Moore search algorithm implementation
(class template)
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