Re: [Boost-users] A forward iterator need not be default-constructible

Subject: Re: [Boost-users] A forward iterator need not be default-constructible
From: Dave Abrahams (dave_at_[hidden])
Date: 2011-09-30 11:23:28

on Fri Sep 30 2011, Krzysztof Żelechowski <giecrilj-AT-stegny.2a.pl> wrote:

> Dave Abrahams wrote:
>
>> make it copyable, for example.  A wrapper over a plain pointer could
>> initialize the pointer to 0.  Now it's a valid past-the-end iterator
>> into an array of length zero.  Such an iterator is also comparable with
>> other iterators into the same sequence.  That's actually far from
>> being minimally singular.
>> 
>
> I doubt there may be a sequence of length 0 at NULL.  How would you allocate 
> such a sequence?

It already exists.

   char* p = 0;
   p == p;     // defined behavior
   p - p;      // defined behavior
   p + 0;      // defined behavior

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com