Re: [boost] [Pointer Container] Modification of pointer containers to allow const elements

Subject: Re: [boost] [Pointer Container] Modification of pointer containers to allow const elements
From: Scott McMurray (me22.ca+boost_at_[hidden])
Date: 2010-10-15 17:35:30

On Fri, Oct 15, 2010 at 13:04, Gerardo Hernandez
<g.hernandez_at_[hidden]> wrote:
>
> I see the point. But I do not understand the advantage of using a
> single underlying type instead of two (which I presume was also
> Thorsten idea).
>

It's the same advantage as using the same underlying type for
ptr_vector<int> and ptr_vector<string>: instantiating less code.

>
> Using always void* would not only require a lot of
> const_cast when returning data from the containers
>

Not a big deal, since it already has to static_cast everywhere when
returning data from the containers.

>
> but also think that
> ptr_vector<T>::iterator must be of different type as ptr_vector<const
> T>::iterator, as:
>
> boost::ptr_vector<const int> v;
> v.push_back(new int);
> (*v.begin()) = 2;
>
> shall also be compiler error, as the container contains const elements.
>

Again, ptr_vector<int> and ptr_vector<string> also need different
iterators, despite using the same underlying type, so ptr_vector<int>
and ptr_vector<const int> will have different iterator types as well,
even though they'd both wrap the same internal iterator type.  And
just like above, they'll just need to const_cast in addition to the
static_casts that are already there.

~ Scott