Implement details of std::tuple

Question

This website teach us how to implement a simple std::tuple, but there are a piece of codes I do not understand

template <size_t k, class... Ts> typename std::enable_if< k == 0, typename elem_type_holder<0, tuple<Ts...>>::type&>::type get(tuple<Ts...>& t) { return t.tail; } template <size_t k, class T, class... Ts> typename std::enable_if< k != 0, typename elem_type_holder<k, tuple<T, Ts...>>::type&>::type get(tuple<T, Ts...>& t) { //Why t could assign to different type? tuple<Ts...>& base = t; return get<k - 1>(base); }

My question is

tuple<T, Ts...>

and

tuple<Ts...>

are different types, how could it work?

Edit : I think I found the answer, because

tuple<Ts...>

is base class of

tuple<T,Ts...>

In the second case Ts... type list can consist of T, Ts... so they can be the same type. — user7860670
– user7860670, Commented Jan 6, 2018 at 14:43
@meplomene yes, I know, my unfamiliar with variadic template blind my eye at first — StereoMatching
– StereoMatching, Commented Jan 6, 2018 at 14:48

HolyBlackCat · Accepted Answer · 2018-01-06 14:43:18Z

1

Probably tuple<T, Ts...> inherits from tuple<Ts...>.

answered Jan 6, 2018 at 14:43

HolyBlackCat

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