From: David Abrahams (dave_at_[hidden])
Date: 2007-11-15 08:14:04
on Fri Nov 09 2007, "JOAQUIN LOPEZ MU?Z" <joaquin-AT-tid.es> wrote:
> De: David Abrahams <dave_at_[hidden]>
>> on Fri Nov 09 2007, Thorsten Ottosen <nesotto-AT-cs.aau.dk> wrote:
>> > "template<class InputIterator>
>> > typename iterator_traits<InputIterator>::difference_type
>> > distance(InputIterator first, InputIterator last);
>> > 4 Effects: Returns the number of increments or decrements needed
>> to get
>> > from first to last.
>> > 5 Requires: last shall be reachable from first."
>> > How can one ever use decrements to get from first to last?
>> When InputIterator is a random access iterator, last < first does not
>> violate the precondition.
> I'm afraid (last<first) violates the precondition even with
> random access iterators, according to 24.1.6 and as explicitly
> acknowledged at
> http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-closed.html#204 .
I don't see how to read the issue resolution so it says that.
> This is IMHO an unfortunate decision by the committee and renders
> the "or decrements" bit in the effects clause of std::distance
> void and misleading.
I do agree that the decision is unfortunate. The wording is clearly
-- Dave Abrahams Boost Consulting http://www.boost-consulting.com
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