Simulate std::tie's functionality for the input iterators.

tie_from.cc

#include <tuple>

template <typename Iter, typename T1>
inline auto tie_from(Iter it, T1& t1)
	-> std::tuple<T1&>
{
	t1 = *it;
	return std::tuple<T1&>(t1);
}

template <typename Iter, typename T1, typename... T2>
inline auto tie_from(Iter it, T1& t1, T2&... t2)
	-> std::tuple<T1&, T2&...>
{
	t1 = *it++;
	return std::tuple_cat(std::tuple<T1&>(t1), tie_from(it, t2...));
}

#include <iostream>
#include <list>

int main()
{
	std::list<int> ls = { 3, 4, 5 };
	int x, y;
	auto t = tie_from(begin(ls), x, y);
	std::cout << x << ' ' << y << std::endl;
	std::get<0>(t) = 8;
	std::cout << x << ' ' << y << std::endl;
}