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

NAME
       std::flat_map::key_comp - std::flat_map::key_comp

Synopsis
	  key_compare key_comp() const;	 (since	C++23)

	  Returns  the function	object that compares the keys, which is	a copy
       of this
	  container's constructor argument comp.

Parameters
	  (none)

Return value
	  The key 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.key_comp();

	    for	(const auto it : cont)
	    {
		const bool before = comp_func(it.first,	100);
		const bool after = comp_func(100, it.first);

		std::cout << "Key (" <<	it.first << ','	<< it.second <<	") ";
		if (!before && !after)
		    std::cout << "equivalent to	key (100)\n";
		else if	(before)
		    std::cout << "goes before key (100)\n";
		else if	(after)
		    std::cout << "goes after key (100)\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
	  value_comp returns the function that compares	 keys  in  objects  of
       type value_type
		     (public member function)

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

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