Re: [boost] [MPL][vector] Is there interest in mpl::vector using variadic templates?

Subject: Re: [boost] [MPL][vector] Is there interest in mpl::vector using variadic templates?
From: Peter Dimov (lists_at_[hidden])
Date: 2017-03-03 16:58:23

Bruno Dutra wrote:

> OTOH the void* trick requires that a pack of M void pointers be 
> instantiated when the element at position M is retrieved from a list, so, 
> for a list of N elements, the compiler must instantiate N *distinct* packs 
> of void pointers, because each of these packs have a different size and is 
> thus a distinct type.

Not just that, but the helper function that is required to obtain the Mth 
element is a template instantiation as well.

Saying that we shouldn't use map_from_list because it consumes memory for 
the instantiation is misleading; the alternatives consume memory for 
instantiations as well. Except for __type_pack_element, of course.