home | help 
std::flat_multimap::find(3)    C++ Standard Libary   std::flat_multimap::find(3)

NAME
     std::flat_multimap::find - std::flat_multimap::find

Synopsis
	iterator find( const Key& key );	     (1) (since C++23)
	const_iterator find( const Key& key ) const; (2) (since C++23)
	template< class K >			     (3) (since C++23)
	iterator find( const K& x );
	template< class K >			     (4) (since C++23)
	const_iterator find( const K& x ) const;

	1,2)  Finds  an element with key equivalent to key. If there are several
     elements with
	the requested key in the container, any of them may be returned.
	3,4) Finds an element with key that compares equivalent to the value  x.
     This
	overload participates in overload resolution only if the qualified-id
	Compare::is_transparent  is  valid and denotes a type. It allows calling
     this function
	without constructing an instance of Key.

Parameters
	key - key value of the element to search for
	x   - a value of any type that can be transparently compared with a key

Return value
	An iterator to the requested element. If no such element is found, past-
     the-end (see
	end()) iterator is returned.

Complexity
	Logarithmic in the size of the container.

Example
     // Run this code

      #include <iostream>
      #include <flat_map>

      struct LightKey
      {
	  int x;
      };

      struct FatKey
      {
	  int x;
	  int data[1000]; // a heavy blob
      };

      // As detailed above, the container must use std::less<> (or other  trans-
     parent
      //  Comparator)  to  access  these overloads. This includes standard over-
     loads,
      // such as comparison between std::string and std::string_view.
      bool operator<(const FatKey& fk, const LightKey& lk) { return fk.x < lk.x;
     }
      bool operator<(const LightKey& lk, const FatKey& fk) { return lk.x < fk.x;
     }
      bool operator<(const FatKey& fk1, const FatKey&  fk2)  {	return	fk1.x  <
     fk2.x; }

      int main()
      {
	  // Simple comparison demo.
	  std::flat_multimap<int, char> example{{1,'a'}, {2,'b'}};

	  if (auto search = example.find(2); search != example.end())
	      std::cout << "Found " << search->first << ' ' << search->second <<
     '\n';
	  else
	      std::cout << "Not found\n";

	  // Transparent comparison demo.
	  std::flat_multimap<FatKey, char, std::less<>> example2{{{1, {}}, 'a'},
     {{2, {}}, 'b'}};

	  LightKey lk = {2};
	  if (auto search = example2.find(lk); search != example2.end())
	      std::cout  << "Found " << search->first.x << ' ' << search->second
     << '\n';
	  else
	      std::cout << "Not found\n";

	  // Obtaining const iterators.
	  // Compiler decides whether to return iterator of (non) const type  by
     way of
	  // accessing map; to prevent intentional modification, one of the sim-
     plest
	  // options is to access the map via a constant reference.
	  const auto& example2ref = example2;
	  if (auto search = example2ref.find(lk); search != example2.end())
	  {
	      std::cout  << "Found " << search->first.x << ' ' << search->second
     << '\n';
	  //  search->second = 'c'; // error: assignment of member
				    // 'std::pair<const FatKey, char>::second'
				    // in read-only object
	  }
      }

Output:
      Found 2 b
      Found 2 b
      Found 2 b

See also
	count	    returns the number of elements matching specific key
		    (public member function)
	equal_range returns range of elements matching a specific key
		    (public member function)

http://cppreference.com 	   2024.06.10	     std::flat_multimap::find(3)
home | help