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std::flat_m...t::key_comp(3)   C++ Standard Libary  std::flat_m...t::key_comp(3)

NAME
     std::flat_multiset::key_comp - std::flat_multiset::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. It is the same as value_comp.

Parameters
	(none)

Return value
	The key comparison function object.

Complexity
	Constant.

Example
     // Run this code

      #include <iostream>
      #include <flat_set>
      #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_multiset<int, ModCmp> cont{1, 2, 3, 4, 5};

	  auto comp_func = cont.key_comp();

	  for (const int key : cont)
	  {
	      const bool before = comp_func(key, 100);
	      const bool after = comp_func(100, key);

	      std::cout << '(' << key << ") ";
	      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:
      Key (1) goes before key (100)
      Key (2) goes before key (100)
      Key (3) equivalent to key (100)
      Key (4) goes after key (100)
      Key (5) 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_m...t::key_comp(3)
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