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Difference between revisions of "cpp/utility/functional/boyer moore horspool searcher"

From cppreference.com
< cpp‎ | utility‎ | functional
m (+"1=" to allow "=" without {{=}}. FTM.)
m ({{c}}, <string_view>, +std::quoted)
 
(One intermediate revision by one user not shown)
Line 32: Line 32:
 
The value type of {{tt|RandomIt1}} must be {{named req|DefaultConstructible}}, {{named req|CopyConstructible}} and {{named req|CopyAssignable}}.
 
The value type of {{tt|RandomIt1}} must be {{named req|DefaultConstructible}}, {{named req|CopyConstructible}} and {{named req|CopyAssignable}}.
  
−
For any two values {{tt|A}} and {{tt|B}} of the type {{c|std::iterator_traits<RandomIt1>::value_type}}, if {{c|1= pred(A, B) == true}}, then {{c|1= hf(A) == hf(B)}} shall be {{tt|true}}.
+
For any two values {{tt|A}} and {{tt|B}} of the type {{c|std::iterator_traits<RandomIt1>::value_type}}, if {{c|1= pred(A, B) == true}}, then {{c|1= hf(A) == hf(B)}} shall be {{c|true}}.
  
 
===Parameters===
 
===Parameters===
Line 66: Line 66:
  
 
===Return value===
 
===Return value===
−
If the pattern {{math|[pat_first, pat_last)}} is empty, returns {{c|std::make_pair(first, first)}}.
+
If the pattern {{range|pat_first|pat_last}} is empty, returns {{c|std::make_pair(first, first)}}.
  
−
Otherwise, returns a pair of iterators to the first and one past last positions in {{range|first|last}} where a subsequence that compares equal to {{math|[pat_first, pat_last)}} as defined by {{c|pred}} is located, or {{c|std::make_pair(last, last)}} otherwise.
+
Otherwise, returns a pair of iterators to the first and one past last positions in {{range|first|last}} where a subsequence that compares equal to {{range|pat_first|pat_last}} as defined by {{c|pred}} is located, or {{c|std::make_pair(last, last)}} otherwise.
 
}}
 
}}
  
Line 79: Line 79:
 
#include <algorithm>
 
#include <algorithm>
 
#include <functional>
 
#include <functional>
 +
#include <iomanip>
 
#include <iostream>
 
#include <iostream>
−
#include <string>
+
#include <string_view>
 
   
 
   
 
int main()
 
int main()
 
{
 
{
−
     std::string in = "Lorem ipsum dolor sit amet, consectetur adipiscing elit,"
+
     constexpr std::string_view in =
−
                    " sed do eiusmod tempor incididunt ut labore et dolore magna aliqua";
+
        "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed "
−
     std::string needle = "pisci";
+
        "do eiusmod tempor incididunt ut labore et dolore magna aliqua";
 +
 
 +
     const std::string_view needle{"pisci"};
 +
 
 
     auto it = std::search(in.begin(), in.end(),
 
     auto it = std::search(in.begin(), in.end(),
 
                   std::boyer_moore_horspool_searcher(
 
                   std::boyer_moore_horspool_searcher(
 
                       needle.begin(), needle.end()));
 
                       needle.begin(), needle.end()));
 
     if (it != in.end())
 
     if (it != in.end())
−
         std::cout << "The string " << needle << " found at offset "
+
         std::cout << "The string " << std::quoted(needle) << " found at offset "
 
                   << it - in.begin() << '\n';
 
                   << it - in.begin() << '\n';
 
     else
 
     else
−
         std::cout << "The string " << needle << " not found\n";
+
         std::cout << "The string " << std::quoted(needle) << " not found\n";
 
}
 
}
 
|output=
 
|output=
−
The string pisci found at offset 43
+
The string "pisci" found at offset 43
 
}}
 
}}
  

Latest revision as of 11:27, 24 May 2023

 
C++
 
Utilities library
General utilities
Relational operators (deprecated in C++20)
 
Function objects
Function invocation
(C++17)(C++23)
Identity function object
(C++20)
Transparent operator wrappers
(C++14)
(C++14)
(C++14)
(C++14)  
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)
(C++14)

Negators
(C++17)
Searchers
(C++17)
(C++17)
boyer_moore_horspool_searcher
(C++17)    
Old binders and adaptors
(until C++17*)
(until C++17*)
(until C++17*)
(until C++17*)
(until C++17*)  
(until C++17*)
(until C++17*)(until C++17*)(until C++17*)(until C++17*)
(until C++20*)
(until C++20*)
(until C++17*)(until C++17*)
(until C++17*)(until C++17*)

(until C++17*)
(until C++17*)(until C++17*)(until C++17*)(until C++17*)
(until C++20*)
(until C++20*)
 
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.

Contents

[edit] 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.

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_boyer_moore_searcher 201603L (C++17) searchers

[edit] 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

[edit] See also

 searches for the first occurrence of a range of elements
(function template) [edit]
(C++17)
 standard C++ library search algorithm implementation
(class template) [edit]
(C++17)
 Boyer-Moore search algorithm implementation
(class template) [edit]
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