[boost] Re: [pointer container] copyability

From: David Abrahams (dave_at_[hidden])
Date: 2005-04-28 08:33:17

Aleksey Gurtovoy <agurtovoy_at_[hidden]> writes:

> David Abrahams writes:
>> "Thorsten Ottosen" <nesotto_at_[hidden]> writes:
>>> the second reason is that value-based and OO programming are different
>>> and are best kept seperate; there are different idioms, different
>>> parts of the langauge is being used.  
>>
>> That's a very paternalistic approach to library design, and rather
>> unprecedented.  Normally the only reason to make functionality that
>> you're implementing anyway hard to access is that it introduces
>> potential correctness problems, e.g. undefined behavior.  Efficiency
>> considerations are usually only used when deciding whether or not to
>> provide functionality at all. for example, that's why we don't have
>> std::vector::push_front.
>
> To be fair, usually the "disabled" functionality is still available
> through other means, e.g. you can still do
>
>     v.insert( v.begin(), ... ) // == v.push_front( ... )
>
> and
>
>     std::advance( bi, n ) // == bi + n

Yes, but the other part of the convention in those cases is that we
only do it when there's a big-O difference.  In the case of
ptr_container clone() is O(N) just like a copy construction would be
for any other container.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com