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

NAME
       std::multimap::value_comp - std::multimap::value_comp

Synopsis
	  std::multimap::value_compare value_comp() const;

	  Returns  a  function	object that compares objects of	type std::mul-
       timap::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 <cassert>
	#include <iostream>
	#include <map>

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

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

	    auto comp_func = cont.value_comp();

	    const std::pair<int, char> val = { 100, 'a'	};

	    for	(auto it : cont) {
		bool before = comp_func(it, val);
		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
		    assert(0); // Cannot happen
	    }
	}

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		  2022.07.31	  std::multimap::value_comp(3)

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