Re: [boost] Iterator adaptor documentation

From: Thomas Witt (witt_at_[hidden])
Date: 2002-01-25 10:07:17

On Friday 25 January 2002 15:10, you wrote:
> ----- Original Message -----
> > My personal opinion is that an iterator_adaptor that exposes its base
> > iterator is dangerous and error prone. Thank of an cyclic iterator that
>
> wraps
>
> > around when it encounters the end iterator of the sequence. You can
> > safely assume that this iterator is always dereferencable unless somebody
> > fiddles with base(). The same problem applies to any adaptor that
> > modifies the sequencing behaviour.
>
> Yes, I understand the problem.
>
> However, since so few compilers support friend templates, I don't see an
> easy solution to that other than saying "don't touch". Do you?
>

You are confusing me. 

For me this is a friend template

class A
{
  template <class T> friend class B;
};

but we need:

template <class T>
class C
{
  friend class T;
};

Though gcc-2.95.3 and edg in ms mode accept

template <class T>
class C
{
   friend T;
};

I think neither this nor the solution above is legal with regard to the 
standard. To be more accurate it looks like this problem is not covered by 
the standard.

To me it feels like an omission. Anyway if it is so we wont be able to fix it 
any time soon.

Thomas

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-- 
Dipl.-Ing. Thomas Witt
Institut fuer Verkehrswesen, Eisenbahnbau und -betrieb, Universitaet Hannover
voice: [phone] - 4273, fax: [phone]
http://www.ive.uni-hannover.de