How can I bubble last element in the variadic templates?

Question

I have template function that get variadic templates as (for example) as (int, int, double)

template<class... Arg>
void
bubble(const Arg &...arg)
{ another_function(arg...); }

Inside the function, I must call with a different order of parameters (double, int, int). How can I implement this?

https://stackoverflow.com/questions/20162903/template-parameter-packs-access-nth-type-and-nth-element might help — An0num0us, Nov 23 '17 at 16:42

Jarod42 · Accepted Answer · 2017-11-23T19:15:17.060

4

With std::index_sequence, you may do something like:

template <typename Tuple, std::size_t ... Is>
decltype(auto) bubble_impl(const Tuple& tuple, std::index_sequence<Is...>)
{
    constexpr auto size = sizeof...(Is);
    return another_function(std::get<(Is + size - 1) % size>(tuple)...);
}


template <class... Args>
decltype(auto) bubble(const Args &...args)
{
    return bubble_impl(std::tie(args...), std::index_sequence_for<Args...>{});
}

edited Nov 23 '17 at 19:15

answered Nov 23 '17 at 16:49

Jarod42

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Thanks. But I have one more question. How to change this code if another_function has returned value(int)? – Hait Nov 23 '17 at 17:12
@Hait: Simply by adding return type and return :) – Jarod42 Nov 23 '17 at 17:23

How can I bubble last element in the variadic templates?

1 Answers1