Re: [boost] Re: mpl/loki

From: Joel de Guzman (djowel_at_[hidden])
Date: 2003-07-12 18:21:08

David Abrahams <dave_at_[hidden]> wrote:
> Aleksey Gurtovoy <agurtovoy_at_[hidden]> writes:
> 
>> IMO we should just stop using 'void_' for internal purposes and give it
>> up to users :).
> 
> I am still unsure about 'void_' being better than 'nil' or
> 'null'....  Users already have a type, 'void', which means void.
> There's no correspondence between void_ and void the way there is
> between bool_ and bool.

IMO, there is. For example, the new TR1 tuples implementation 
(it's feature complete and in the sandbox now BTW) uses void_
as it would a void tuple element. nil_t or something would do, but 
we'll need to convert this to void_ simply because MPL expects void_.

Admittedly, the void_ is not part of its public API and the use should 
not care about it, *but* you have to consider that the tuple lib *IS* a 
client of MPL. As such, it needs the mpl_void_ as a *public* API. 
Another good example is Phoenix/LL. We are using void_ much as 
a void argument to something. Here now, there is a direct mapping
to our C++ void. Again, the void_ is not part of Phoenix's  public API 
but then again, it *is* a client of MPL.

-- 
Joel de Guzman
joel at boost-consulting.com
http://www.boost-consulting.com
http://spirit.sf.net