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

	  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
	  Iterator  to	an element with	key equivalent to key. If no such ele-
       ment is found,
	  past-the-end (see end()) iterator is returned.

Complexity
	  Logarithmic in the size of the container.

Notes
	  Feature-test macro: __cpp_lib_generic_associative_lookup (for	 over-
       loads (3,4))

Example
       // Run this code

	#include <iostream>
	#include <map>

	struct FatKey	{ int x; int data[1000]; };
	struct LightKey	{ int x; };
	//  Note:  as  detailed	 above,	the container must use std::less<> (or
       other
	//   transparent Comparator) to	access these overloads.
	// This	includes standard overloads, such as 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'}};

	    auto search	= example.find(2);
	    if (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};
	    auto search2 = example2.find(lk);
	    if (search2	!= example2.end()) {
		std::cout  <<  "Found  "  <<  search2->first.x	<<  "	"   <<
       search2->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 modification	on purpose, one	of easiest choices  is
       to access map by
	// const reference.
	    const auto&	example2ref = example2;
	    auto search3 = example2ref.find(lk);
	    if (search3	!= example2.end()) {
		std::cout   <<	 "Found	 "  <<	search3->first.x  <<  '	 '  <<
       search3->second << '\n';
	    //	search3->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		  2022.07.31		     std::map::find(3)

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