C++ enumerate (끔찍한 흑마술입니다)

enumerate.cpp

#include<iostream>
#include<set>
#include<utility>
#include<cstdlib>
#include<ctime>
using namespace std;

template<class T>
struct enum_iter
{
	T it;size_t idx;
	enum_iter& operator++()
	{
		idx++;it++;
	}
	enum_iter operator++(int)
	{
		enum_iter tmp{it,idx};idx++;it++;return tmp;
	}
	bool operator!=(enum_iter i)
	{
		return it!=i.it;
	}
	pair<size_t,decltype(*it)> operator*()
	{
		return {idx,*it};
	}
};
template<class T>
struct enumerate
{
	T& cont;
	using iter=T::iterator;
	enumerate(T& t):cont(t){}
	enum_iter<iter> begin(){return enum_iter{cont.begin(),0};}
	enum_iter<iter> end(){return enum_iter{cont.end(),cont.size()};}
};

int main()
{
	srand(time(0));
	set<int> S;
	for(int i=0;i<10;i++)
	S.insert(rand());
	for(auto[i,k]:enumerate(S))cout<<i<<" "<<k<<endl;
}