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

Subject: Re: [boost] [mpl][docs]why use list?
From: Larry Evans (cppljevans_at_[hidden])
Date: 2009-03-27 12:00:40

On 03/23/09 05:40, Larry Evans wrote:
 > On 03/21/09 11:31, Steven Watanabe wrote:
[snip]
 >  > Also, it is possible for memoization to reduce the number of
 >  > template instantiations when iterating over lists with identical
 >  > tails, iterators into distinct vectors always have different types.
 >
 > Thank you.  This is what I needed to know.  In summary.
 >
[snip]

Hi Steven,

After viewing the code some more, I'm wondering if the memoization is
not also possible with vectors with identical tails.  That's because,
from:

 
https://svn.boost.org/trac/boost/browser/trunk/boost/mpl/vector/aux_/preprocessed/typeof_based/vector10.hpp

containing:

   template<
39	      typename T0, typename T1, typename T2
40	    >
41	struct vector3
42	    : v_item<
43	          T2
44	        , vector2< T0,T1 >
45	        >
46	{
47	    typedef vector3 type;
48	};

it appears that vector would have a memoization advantage for idential
heads. For instance:

   vector<T0,T1,T2_1> vs vector<T0,T1,T2_2>

from the above vector3 code:

   v_item<T2_1,vector2<T0,T1> > vs v_item<T2_2,vector2<T0,T1> >

So, maybe list has an advantage for identical tails but vector has an
advantage for identical heads?

-regards,
Larry