Здравейте !

Имам бърз въпрос по тази задача :

NOTE: this task is the same as Task 3 – Parser, however the output is sorted depending on the object.
You are given code that reads objects from the console, each from a separate line, until a “stopLine” is entered. The format of the input is the following
•	A character called type, which determines the type of each object – i for integer, w for string, and s for Song
•	A line representing the stopLine 
•	Lines, each containing a single object, until a line matching the stopLine is reached – the program should not read anything after the stopLine.
The program then uses a set to store and then print all unique the objects on a single line, sorted in descending order, separated by single spaces. Descending order is different for each object type:
•	For integers, it is the same as the standard C++ ordering of integers, in reverse, i.e. larger numbers are placed before smaller numbers
•	For strings, it is the reverse of the C++ lexicographical order of strings
•	For Songs, it is a reverse ordering by the lengthSeconds field, i.e. longer Songs are placed before shorter Songs
Your task is to study the available code and create any necessary files for the program to compile and work correctly.
You should submit a single .zip file for this task, containing ONLY the files YOU created. The Judge system has a copy of the other files and will compile them, along with your files, in the same directory.
Restrictions
Each type of object supports stream insertion operator<<
Each object is valid, meaning that each line representing an object can be turned into an object of the appropriate type through stream extraction operator>>
Examples

Скелета който е даден е следният :

#include <iostream>
#include <string>
#include <set>

#include "Song.h"
#include "Parser.h"
#include "Comparators.h"
#include "PrintUtils.h"

std::ostream& operator<<(std::ostream& out, const Song& s) {
	return out << s.getName() << " " << s.getLengthSeconds();
}

std::istream& operator>>(std::istream& in, Song& s) {
	std::string name; int length;
	in >> name >> length;

	s = Song(name, length);
	return in;
}

int main() {
	char type;
	std::cin >> type; std::cin.ignore();
	std::string stopLine;
	std::getline(std::cin, stopLine);

	if (type == 'i') {
		Parser<int> p(std::cin, stopLine);
		int n;
		typedef std::set<int, Reverse<int, LessThan<int> > > Set;
		Set numbers;
		while (p.readNext(n)) {
			numbers.insert(n);
		}
		printContainer<Set>(numbers.begin(), numbers.end());
	}
	else if (type == 'w') {
		Parser<std::string> p(std::cin, stopLine);
		std::string w;
		typedef std::set<std::string, Reverse<std::string, LessThan<std::string> > > Set;
		Set words;
		while (p.readNext(w)) {
			words.insert(w);
		}
		printContainer<Set>(words.begin(), words.end());
	}
	else if (type == 's') {
		Parser<Song> p(std::cin, stopLine);
		Song s;
		typedef std::set<Song, Reverse<Song, LessThan<Song> > > Set;
		Set songs;
		while (p.readNext(s)) {
			songs.insert(s);
		}
		printContainer<Set>(songs.begin(), songs.end());
	}
	else {
		std::cout << "[invalid input]" << std::endl;
	}

	return 0;
}

Не мога да разбера какво прави този сет ! Всякаш този pair<T, Reverse<T, LessThan<T > > > ( самият сет ) pair.first е това n, обаче самата логика на Reverse не мога да я хвана. Може ли някой да ме насочи на някъде ( говоря за логиката със сета с другото ще се оправя :) ).