Re: [boost] [mpl][docs]why use list?

Subject: Re: [boost] [mpl][docs]why use list?
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2009-03-29 15:35:36

AMDG

Larry Evans wrote:
> Now, on a related matter,
>
> what's the rationale for vector0::lower_bound_::value == 32768

push_front decreases lower_bound_, and the lower_bound_ needs to
stay positive.  the lower_bound_ in vector zero needs to be fairly high
to avoid problems.  There is no reason why it has to be exactly 32768.

> as shown here:
>
>
> https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/vector/aux_/vector0.hpp#L35 
>
>
> and what's the rationale for at_front=0 here:
>
>
> https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/vector/aux_/item.hpp#L31 
>
>
> The only reason, AFAICT, for the at_front value is that the vectorI
> specializations here:
>
>
> https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/vector/aux_/preprocessed/typeof_based 
>
>
> for some reason add items starting from the tail, as shown at:
>
>
> https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/vector/aux_/preprocessed/typeof_based/vector10.hpp#L43 
>
>
> However, if the items were added from the head, then at_front=1 could
> be used.  The reason that would be desirable is that it enables the
> variadic template compiler to used to simplify the mpl::vector
> implementation, as shown here:
>
>   TinyURL.com/cof5br
at_front indicates whether to use push_front or push_back.  It's
really a bool not an int.

In Christ,
Steven Watanabe