enumerate.cc

template <typename Cont>
struct enumeration {
	enumeration(Cont &c)
	:_c{c}, _begin{c.begin(), 0}, _end{c.end(), c.size()}
	{}

private:
	struct enumeration_iterator {
		typename Cont::iterator it;
		typename Cont::size_type n;

		enumeration_iterator &operator++() {
			it++;
			n++;
			return *this;
		}

		auto operator*() {
			struct {
				typename Cont::size_type n;
				typename Cont::value_type &v;
			} e{n, *it};
			return e;
		}

		bool operator!=(enumeration_iterator &other) {
			return it != other.it || n != other.n;
		}
	};

public:
	enumeration_iterator begin() {
		return _begin;
	}

	enumeration_iterator end() {
		return _end;
	}

private:
	Cont &_c;

	enumeration_iterator _begin, _end;
};

template <typename Cont>
enumeration<Cont> enumerate(Cont &c) {
	return enumeration<Cont>{c};
}