Obtain Argument Index while Unpacking Argument List with Variadic Templates

Question

I need to obtain the index of an argument while unpacking and converting argument list. Is there any solution for the following problem:

Answer 1

The simplest solution is surely to not use a vector of void*; just use the values directly:

template
void call_test(Arg const&...arg) {
  test(arg...);
}

(Or some variant on that theme.) But I suppose you wanted to do something other than just call test.

If you really want the indices, use what's called here the "indices trick". You should be able to search for that.