GCC (in any version) equivalent of clang's __type_pack_element to get Nth element of template parameter pack

Question

https://reviews.llvm.org/D15421

clang has __type_pack_element which allows efficient indexing of parameter packs in variadic templates. Is there a GCC equivalent?

I am not interested in using tuple_element_t. I am looking for an alternative that is a compiler primitive

Answer 1

If you are really brave/crazy you could try and use the same techniques as kvasir::mpl does for this problem. In metaben.ch benchmarks its the same or faster than others who use __type_pack_element and works on GCC (note that the benchmark looks at every element, if you just ever index a few it will look quite different but usually if you want one then you eventually want the others too).

benchmark

implementation

old blog post about it