std::default_searcher

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

#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

searches for a range of elements
(function template)

© cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
http://en.cppreference.com/w/cpp/utility/functional/default_searcher