Re: [boost] [intrusive] Intrusive containers library strikes back

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2006-09-18 10:38:03

Bruno Martínez wrote:
> On Wed, 13 Sep 2006 04:12:03 -0300, Ion Gaztañaga <igaztanaga_at_[hidden]>  
> wrote:
> 
>> If someone needs/wants more features, now's the time to request them!
> 
> I think intrusive containers would be useful.  There was a separate  
> initiative that added intrusiveness to the multi index library.  I think  
> it would be better to fold the many STL remakes that are popping up  
> (pointer containers, intrusive containers/shared mem containers) into  
> multi index than repeat the effort everywhere.  Case in point: what do I  
> do if I need a pointer-sharedmem-bimap?

Good point. But the problem is that users also want simple STL-like 
classes and they don't want to start using a class that offers a lot of 
additional features. That multi_index class might be also more expensive 
so using a multi_index as a simple single-index class can be a bad idea.

If a user just wants an intrusive linked list class, I suppose that 
he/she expects sizeof(ilist) == 2*sizeof(void *) (plus an optional size 
member if he/she wants constant-time size() member). A list user might 
also want a non-constant size() member but a constant time splice(), etc...

Another problem is the coordination between libraries and authors. 
Having a single library with a lot functionalities can be very difficult 
to maintain and it would require coordination between several authors.

If you want to have shared memory multi_index you need to change 
multi_index implementation to accept a templatized pointer type. That 
can be really a big task. It's not something a wrapper can solve. Maybe 
ptr container can also offer wrapper over user-provided classes apart 
from using STL containers, so that we can have a ptr_vector based on a 
shared memory vector. Again, it would require support for non-raw 
pointers. But it would be nice to have some *core* algorithms somewhere 
(surely intrusive, multi_index, and intrusive_multi_index have their own 
version). Other Boost have also those algorithms as internal files. For 
example, boost/detail has rb tree algorithm implementation.

Regards,

Ion