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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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