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std::flat_map::value_comp(3)  C++ Standard Libary std::flat_map::value_comp(3)

NAME
       std::flat_map::value_comp - std::flat_map::value_comp

Synopsis
	  std::flat_map::value_compare value_comp() const;  (since C++23)

	  Returns   a	function   object   that   compares  objects  of  type
       std::flat_map::value_type
	  (key-value pairs) by using key_comp to compare the first  components
       of the pairs.

Parameters
	  (none)

Return value
	  The value comparison function	object.

Complexity
	  Constant.

Example
       // Run this code

	#include <iostream>
	#include <flat_map>
	#include <utility>

	// Example module 97 key compare function
	struct ModCmp
	{
	    bool operator()(int	lhs, int rhs) const
	    {
		return (lhs % 97) < (rhs % 97);
	    }
	};

	int main()
	{
	    std::flat_map<int, char, ModCmp> cont;
	    cont = {{1,	'a'}, {2, 'b'},	{3, 'c'}, {4, 'd'}, {5,	'e'}};

	    auto comp_func = cont.value_comp();

	    for	(const std::pair<int, char> val	= {100,	'a'}; auto it :	cont)
	    {
		const bool before = comp_func(it, val);
		const bool after = comp_func(val, it);

		std::cout << '(' << it.first <<	',' << it.second << ") ";
		if (!before && !after)
		    std::cout << "equivalent to	key (" << val.first << ")\n";
		else if	(before)
		    std::cout << "goes before key (" <<	val.first << ")\n";
		else if	(after)
		    std::cout << "goes after key (" << val.first << ")\n";
		else
		    std::unreachable();
	    }
	}

Output:
	(1,a) goes before key (100)
	(2,b) goes before key (100)
	(3,c) equivalent to key	(100)
	(4,d) goes after key (100)
	(5,e) goes after key (100)

See also
	  key_comp returns the function	that compares keys
		   (public member function)

http://cppreference.com		  2024.06.10	  std::flat_map::value_comp(3)

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