details of std::make_index_sequence and std::index_sequence

Question

I\'m enjoying ramping up on variadic templates and have started fiddling about with this new feature. I\'m trying to get my head around the implementation details of s

Answer 1

For the sake of completeness, I'll add a more modern implementation of std::make_index_sequence, using if constexpr and auto, that make template programming a lot more like "normal" programming.

template 
struct index_sequence {};

template 
auto make_index_sequence_impl() {
    // only one branch is considered. The other may be ill-formed
    if constexpr (N == 0) return index_sequence(); // end case
    else return make_index_sequence_impl(); // recursion
}

template 
using make_index_sequence = std::decay_t())>;

I strongly advise to use this style of template programming, which is easier to reason about.