Re: [boost] [interprocess][circular_buffer] specialized containers should have container template argument

Subject: Re: [boost] [interprocess][circular_buffer] specialized containers should have container template argument
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2009-05-04 14:44:22

Ion Gaztañaga skrev:
> Thorsten Ottosen wrote:
>> However, we can make them faster if you allow a new template argument. 
>> For example
>>   template
>>   <
>>     typename T,
>>     typename Pred,
>>     typename Alloc
>>         class PushBackContainer = /* some default */
>>   >
>>   class flat_set;
>>
>> My motivation is that these can perform somewhat better e.g. with an 
>> array (for circular_buffer), or auto_buffer (for flat_set/flat_map).
>> I think even some very simply array wrapper would be useable with
>> flat_set.
> 
> Interesting, but it seems that PushBackContainer and Allocator overlap. 

Right. But see below.

> auto_buffer is basically an allocator. But flat_xxx could be implemented 
> in any sequence container with random-access iterators (we need them for 
> binary search), so maybe it could be interesting to have more generic 
> classes like map_sequence<>, set_sequence (names are horrible I know, 
> but it's just an example):
> 
> template<class Sequence>
> class set_sequence;
> 
> set_sequence<vector<T>>
> set_sequence<deque<T>>
> 
> or something more similar to std::queue:
> 
> template<class T, class Sequence>
> class set_sequence;
> 
> 
> 
> Anyway, my opinion is that we should only use a minimal interface for 
> Sequence ((r/c)begin,(r/c)end, insert, erase, clear()).

I think you only need:

begin() [const and non-const]
end()   [ditto]
insert()
erase() [clear will be defined in terms of erase]

> Another option would be something like:
> 
> template< class T
>         , class Allocator
>         , class Sequence = vector<T, A>
>         >
> flat_set;
> 
> and we should require (as we require for allocator::value_type) that 
> Sequence::value_type is T and Sequence::allocator_type is Allocator.

Right on. We currently have:

template< class T
         , class Allocator
         , class Pred
 >
flat_set;

So just do

template< class T
         , class Allocator
         , class Pred
         , class Sequence = vector<T, Allocator>
         >
flat_set;

>> The EA STL implementation has this features.
> 
> I will look at this. Is there any public

Don't think so. It's described in

   http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2271.html

>>
>> What do you think?
> 
> These days I don't have much time and I have other improvements with 
> higher priority but I will add to the to-do list.
> 

Thanks ... it doesn't have high priority.

-Thorsten