NAME

std::boyer_moore_searcher - std::boyer_moore_searcher

Synopsis

Defined in header <functional>
template< class RandomIt1,

class Hash = std::hash<typename
std::iterator_traits<RandomIt1>::value_type>, (since C++17)
class BinaryPredicate = std::equal_to<> >

class boyer_moore_searcher;

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

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 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 (since C++17)
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: __cpp_lib_boyer_moore_searcher

Example

// Run this code

#include <iomanip>
#include <iostream>
#include <algorithm>
#include <functional>
#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 " << 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