Re: [boost] [ptr_container] iterators bug

From: David Abrahams (dave_at_[hidden])
Date: 2005-06-15 11:01:27

Jonathan Wakely <cow_at_[hidden]> writes:

> On Wed, Jun 15, 2005 at 10:24:10AM +0200, Thorsten Ottosen wrote:
>
>> "David Abrahams" <dave_at_[hidden]> wrote in message 
>> news:uk6kws88y.fsf_at_boost-consulting.com...
>> 
>> | If someone would clearly and succinctly spell out the question, I'd be
>> | happy to.
>> 
>> should one be able to add, subtract, and compare mutable random access 
>> iterators with
>> random access const_iterators provided they point to the same container?
>
> It's not required for any iterator in general (you can't convert all
> output iterators to input iterators, for instance ostream_iterator
> cannot be converted to a read-only iterator type).
>
> But the container requirements require that X::iterator be convertible
> to X::const_iterator, and then all those operations work by using that
> conversion.  

That's incorrect.  For example, if the operations are templated no
implicit conversion will take place.

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