std::default_searcher

 

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Defined in header <functional>
template< class ForwardIt, class BinaryPredicate = std::equal_to<> > class default_searcher;		(since C++17)

A class suitable for use with Searcher overload of std::search that delegates the search operation to the pre-C++17 standard library's std::search.

default_searcher is CopyConstructible and CopyAssignable.

Member functions

std::default_searcher::default_searcher

default_searcher( ForwardIt pat_first,                   ForwardIt pat_last,                   BinaryPredicate pred = BinaryPredicate());		(since C++17) (until C++20)
constexpr default_searcher( ForwardIt pat_first,                             ForwardIt pat_last,                             BinaryPredicate pred = BinaryPredicate());		(since C++20)

Constructs a default_searcher by storing copies of pat_first, pat_last, and pred

Parameters

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

Exceptions

Any exceptions thrown by the copy constructors of BinaryPredicate or ForwardIt.

std::default_searcher::operator()

template< class ForwardIt2 > std::pair<ForwardIt2, ForwardIt2>     operator()( ForwardIt2 first, ForwardIt2 last ) const;		(since C++17) (until C++20)
template< class ForwardIt2 > constexpr std::pair<ForwardIt2, ForwardIt2>     operator()( ForwardIt2 first, ForwardIt2 last ) const;		(since C++20)

The member function called by the Searcher overload of std::search to perform a search with this searcher.

Returns a pair of iterators i, j, where i is std::search(first, last, pat_first, pat_last, pred) and j is std::next(i, std::distance(pat_first, pat_last)) unless std::search returned last (no match), in which case j equals last as well.

Parameters

first, last

-

a pair of iterators designating the string to be examined

Return value

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 a pair of copies of last otherwise.

Example

Run this code

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

Output:

The string pisci found at offset 43

See also

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