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std::map::find(3)	      C++ Standard Libary	     std::map::find(3)

NAME
       std::map::find -	std::map::find

Synopsis
	  iterator find( const Key& key	);	       (1)
	  const_iterator find( const Key& key )	const; (2)
	  template< class K >			       (3) (since C++14)
	  iterator find( const K& x );
	  template< class K >			       (4) (since C++14)
	  const_iterator find( const K&	x ) const;

	  1,2) Finds an	element	with key equivalent to key.
	  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 call-
       ing 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.

Notes
		   Feature-test	      macro		    Value	   Std
       Feature
							       Heterogeneous
       comparison lookup
	  __cpp_lib_generic_associative_lookup	201304L	(C++14)	in associative
       containers;
							       overloads (3,4)

Example
       // Run this code

	#include <iostream>
	#include <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
       transparent
	// 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::map<int, char>	example{{1,'a'}, {2,'b'}};

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

	    // Transparent comparison demo.
	    std::map<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
       simplest
	    // 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>::sec-
       ond'
				      // 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::map::find(3)

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