Implementation of a binding element

sorted_view_cpp17_sorted_element.cpp

template <class T>
struct sorted_element
{
	std::remove_reference_t<T>* _data;
	std::vector<std::size_t> const* _is;

	sorted_element(T& elem, std::vector<std::size_t> const& is)
	    : _data(&elem), _is(&is)
	{
	}

	decltype(auto) operator[](std::size_t i)
	{
		return _data->at(_is->at(i));
	}
};