std::boyer_...ol_searcher(3)

💅 std::boyer_...ol_searcher(3) — C++ Standard Libary realness

Okay bestie, this is the manual page for std::boyer_...ol_searcher(3) from the C++ Standard Libary, and we are about to make search algorithms make sense. No cap. 🫶

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🌸 NAME 🌸

std::boyer_moore_horspool_searcher — and yeah, that’s also the NAME line, because this page said it twice and we respect the duplication era. 💅

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✨ Synopsis ✨

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;

This class has been around (since C++17), icon behavior only. ⭐

It’s a searcher suitable for use with the Searcher overload of std::search that implements the Boyer-Moore-Horspool string searching algorithm. That’s the whole vibe: a searcher made for that specific std::search overload, implementing Boyer-Moore-Horspool.

std::boyer_moore_horspool_searcher is CopyConstructible and CopyAssignable. Copy girlies, rise. 🎀

RandomIt1 must meet the requirements of LegacyRandomAccessIterator. Periodt.

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🧚 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() );

This constructor 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. Very “I made copies and I’m organized about it” of it. 💖

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. That’s the rule, bestie. 🦋

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🌸 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

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💀 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. So yeah, memory said “not today” possibly. 😭

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🔍 std::boyer_moore_horspool_searcher::operator()

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

This is 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. Matching value types only, iykyk. 💅

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🌸 Parameters 🌸

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

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🎀 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. Found bestie or not-found bestie, no in-between. ✨

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👑 Notes 👑

Feature-test macro realness:

• __cpp_lib_boyer_moore_searcher — 201603L — (C++17) — searchers

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🌈 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

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🦋 See also 🦋

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

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xoxo, your Unix bestie 🫶 source/version/date: http://cppreference.com, 2024.06.10, std::boyer_...ol_searcher(3). Slay. 💅✨