Subject: Re: [boost] [odeint] Iterator semantics
From: Karsten Ahnert (karsten.ahnert_at_[hidden])
Date: 2012-08-19 04:30:07
On 08/19/2012 02:57 AM, Dave Abrahams wrote:
>
> on Fri Aug 10 2012, Karsten Ahnert <karsten.ahnert-AT-ambrosys.de> wrote:
>
>> I tried to find different solutions but it is difficult since one is
>> more or less always checking for overlap. On the other hand I wonder if
>> the requirement of transitivity can be relaxed in this case. I can not
>> imagine an algorithm where the above situation might occur. The iterator
>> is a single pass iterator which limits the number of possible
>> algorithms. Furthermore the violation can only appear if two end
>> iterators are used. This is not the case for all algorithms in the
>> standard and Boost.Range.
>>
>> Any ideas or comments? Is it really necessary to require transitivity?
>
> Yes. Transitivity of == is fundamental.
>
Ok. Then, the question is which kind of algorithms will fail. I think
all algorithms where you pass exactly one end-iterator are ok, like
algorithm( first , last , ... )
You simply can not create an iterator for which transitivity which will
in such situations. This is the case for most algorithm in the STL and
boost.range.