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std::search(3)		       C++ Standard Libary		  std::search(3)

NAME
     std::search - std::search

Synopsis
	Defined in header <algorithm>
	template< class ForwardIt1, class ForwardIt2 >

	ForwardIt1  search( ForwardIt1 first, ForwardIt1 last,	  (1) (constexpr
     since C++20)

			   ForwardIt2 s_first, ForwardIt2 s_last
	);
	template< class ExecutionPolicy, class ForwardIt1, class
	ForwardIt2 >

	ForwardIt1  search(  ExecutionPolicy&&	policy, 	     (2)  (since
     C++17)
			   ForwardIt1 first, ForwardIt1 last,

			   ForwardIt2 s_first, ForwardIt2 s_last
	);
	template< class ForwardIt1, class ForwardIt2, class
	BinaryPred >

	ForwardIt1  search( ForwardIt1 first, ForwardIt1 last,	  (3) (constexpr
     since C++20)
			   ForwardIt2 s_first, ForwardIt2
	s_last,

			   BinaryPred p );
	template< class ExecutionPolicy,

		  class ForwardIt1, class ForwardIt2, class
	BinaryPred >
	ForwardIt1  search(  ExecutionPolicy&&	policy, 	     (4)  (since
     C++17)
			   ForwardIt1 first, ForwardIt1 last,
			   ForwardIt2 s_first, ForwardIt2
	s_last,

			   BinaryPred p );
	template< class ForwardIt, class Searcher >
								     (since
     C++17)
	ForwardIt  search( ForwardIt first, ForwardIt last,	  (5) (constexpr
     since C++20)

			  const Searcher& searcher );

	1-4) Searches for the first  occurrence  of  the  sequence  of	elements
     [s_first, s_last)
	in the range [first, last).
	1) Elements are compared using operator==.
	3) Elements are compared using the given binary predicate p.
	2,4) Same as (1,3), but executed according to policy.
	These overloads participate in overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

	5)  Searches  the  range  [first, last) for the pattern specified in the
     constructor of
	searcher.

	The standard library provides the following searchers:

	default_searcher	      standard C++ library search algorithm
	(C++17) 		      implementation
				      (class template)
	boyer_moore_searcher		  Boyer-Moore	   search      algorithm
     (since C++17)
	(C++17) 		      implementation
				      (class template)
	boyer_moore_horspool_searcher Boyer-Moore-Horspool search algorithm
	(C++17) 		      implementation
				      (class template)

Parameters
	first, last	- the range of elements to examine
	s_first, s_last - the range of elements to search for
	policy		 - the execution policy to use. See execution policy for
     details.
	searcher	- the searcher encapsulating the  search  algorithm  and
     the pattern to
			  look for
			  binary  predicate  which  returns true if the elements
     should be
			  treated as equal.

			  The signature of  the  predicate  function  should  be
     equivalent to
			  the following:

			   bool pred(const Type1 &a, const Type2 &b);

	p		- While the signature does not need to have const &, the
     function
			  must	not  modify the objects passed to it and must be
     able to
			  accept all values of type (possibly const)  Type1  and
     Type2
			  regardless of value category (thus, Type1 & is not al-
     lowed
			  ,  nor  is Type1 unless for Type1 a move is equivalent
     to a copy
			  (since C++11)).
			  The types Type1 and Type2 must be such that objects of
     types
			  ForwardIt1 and ForwardIt2 can be dereferenced and then
     implicitly
			  converted to Type1 and Type2 respectively.

Type requirements
	-
	ForwardIt1, ForwardIt2 must meet the requirements of LegacyForwardItera-
     tor.
	-
	BinaryPred must meet the requirements of BinaryPredicate.

Return value
	1-4) Iterator to the beginning	of  first  occurrence  of  the	sequence
     [s_first, s_last)
	in  the range [first, last). If no such occurrence is found, last is re-
     turned.
	If [s_first, s_last) is empty, first is returned.
	5) searcher(first, last).first.

Complexity
	1-4)  Given  \(\scriptsize  N\)N  as  std::distance(first,   last)   and
     \(\scriptsize S\)S
	as std::distance(s_first, s_last):
	1,2) At most \(\scriptsize N\cdot S\)NA.S comparisons using operator==.
	3,4)  At most \(\scriptsize N\cdot S\)NA.S applications of the predicate
     p.
	5) Depends on searcher.

Exceptions
	The overloads with a template parameter named ExecutionPolicy report er-
     rors as
	follows:

	  * If execution of a function invoked as part of the  algorithm  throws
     an exception
	    and  ExecutionPolicy is one of the standard policies, std::terminate
     is called.
	    For any other ExecutionPolicy, the	behavior  is  implementation-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation
				      search (1)
	template<class ForwardIt1, class ForwardIt2>
	constexpr //< since C++20
	ForwardIt1 search(ForwardIt1 first, ForwardIt1 last,
			  ForwardIt2 s_first, ForwardIt2 s_last)
	{
	    while (true)
	    {
		ForwardIt1 it = first;
		for (ForwardIt2 s_it = s_first; ; ++it, ++s_it)
		{
		    if (s_it == s_last)
			return first;
		    if (it == last)
			return last;
		    if (!(*it == *s_it))
			break;
		}
		++first;
	    }
	}
				      search (3)
	template<class ForwardIt1, class ForwardIt2, class BinaryPred>
	constexpr //< since C++20
	ForwardIt1 search(ForwardIt1 first, ForwardIt1 last,
			  ForwardIt2 s_first, ForwardIt2 s_last, BinaryPred p)
	{
	    while (true)
	    {
		ForwardIt1 it = first;
		for (ForwardIt2 s_it = s_first; ; ++it, ++s_it)
		{
		    if (s_it == s_last)
			return first;
		    if (it == last)
			return last;
		    if (!p(*it, *s_it))
			break;
		}
		++first;
	    }
	}

Example
     // Run this code

      #include <algorithm>
      #include <cassert>
      #include <functional>
      #include <iomanip>
      #include <iostream>
      #include <iterator>
      #include <string_view>
      #include <vector>

      using namespace std::literals;

      bool contains(const auto& cont, std::string_view s)
      {
	  // str.find() (or str.contains(), since C++23) can be used as well
	  return  std::search(cont.begin(),  cont.end(),  s.begin(), s.end()) !=
     cont.end();
      }

      int main()
      {
	  const auto str{"why waste time learning, when ignorance  is  instanta-
     neous?"sv};
	  assert(contains(str, "learning"));
	  assert(not contains(str, "lemming"));

	  const std::vector vec(str.begin(), str.end());
	  assert(contains(vec, "learning"));
	  assert(not contains(vec, "leaning"));

	  // The C++17 overload with searchers demo:
	  constexpr auto quote
	  {
	      "Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed "
	      "do eiusmod tempor incididunt ut labore et dolore magna aliqua"sv
	  };

	  for (const auto word : {"pisci"sv, "Pisci"sv})
	  {
	      std::cout << "The string " << std::quoted(word) << ' ';
	      const	  std::boyer_moore_searcher	  searcher(word.begin(),
     word.end());
	      const auto it = std::search(quote.begin(), quote.end(), searcher);
	      if (it == quote.end())
		  std::cout << "not found\n";
	      else
		  std::cout << "found at  offset  "  <<  std::distance(quote.be-
     gin(), it) << '\n';
	  }
      }

Output:
      The string "pisci" found at offset 43
      The string "Pisci" not found

	Defect reports

	The  following	behavior-changing  defect  reports were applied retroac-
     tively to
	previously published C++ standards.

	   DR	 Applied to	      Behavior as published		 Correct
     behavior
	LWG 1205 C++98	    the return value was unclear  if		 returns
     first in this
			    [s_first, s_last) is empty		       case
			    the resolution of LWG issue 1205 was
	LWG  1338  C++98      incorrectly applied,			 returns
     last in this
			    making first to be returned if no	       case
			    occurence is found
	LWG 2150 C++98	    the condition of asequence occurencea was  corrected
			    incorrect

See also
	find_end		      finds the last sequence of elements  in  a
     certain range
				      (function template)
				      returns  true  if one sequence is a subse-
     quence of
	includes		      another
				      (function template)
	equal			      determines if two sets of elements are the
     same
				      (function template)
	find
	find_if 		      finds the first  element	satisfying  spe-
     cific criteria
	find_if_not		      (function template)
	(C++11)
				      returns true if one range is lexicographi-
     cally less
	lexicographical_compare       than another
				      (function template)
	mismatch		       finds the first position where two ranges
     differ
				      (function template)
				      searches a range for a number of	consecu-
     tive copies of
	search_n		      an element
				      (function template)
	default_searcher	       standard C++ library search algorithm im-
     plementation
	(C++17) 		      (class template)
	boyer_moore_searcher	      Boyer-Moore search  algorithm  implementa-
     tion
	(C++17) 		      (class template)
	boyer_moore_horspool_searcher  Boyer-Moore-Horspool search algorithm im-
     plementation
	(C++17) 		      (class template)
	ranges::search		      searches for a range of elements
	(C++20) 		      (niebloid)

http://cppreference.com 	   2024.06.10			  std::search(3)
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