Re: [Boost-users] Re: iterator_adaptor: disguise iterator as const_iterator?

From: Duane Murphy (duanemurphy_at_[hidden])
Date: 2004-12-02 14:01:13

I've started doing a conversion of many old iterators to the new
iterators. I also have been going through the docs, so I thought I would
add a few comments.

--- At Thu, 2 Dec 2004 13:07:48 -0500, David Abrahams wrote:

>Martin Wartens wrote:
> >>> I have to say that the documentation was not of much help to me.
> >>> There are lots of complicated implementation details but only
> >>> small examples.
> >>
> >> You're not kidding?  Did you go through the tutorial starting with
> >>  iterator_facade (http://tinyurl.com/2gzpz#tutorial-example) which
> >>  continues on to the iterator adaptor tutorial
> >> (http://tinyurl.com/58e2p#tutorial-example)?  Gee, it looks from
> >> the below like you did!
> >
> > No, I am serious. Looking at the iterator_facade doc, first of all it
> > does not tell me what it is all about. The one sentence in the
> > abstract is indeed very abstract.
>
>Wow, good point.

The biggest thing missing for me is what the difference is between facade
and adaptor. In particular when would you choose one over the other. I
think i know the answer, but it wasn't clear that the docs explained that
very well.
>
> > I would like to see more examples, if that is possible.
>
>Hm.  Examples of what?

The example with details shows a forward iterator that can also be used
as an adaptor. Clever for continuity, but reality is seldom that cooperative.

I would like to see a full random access facade. For example: build the
full suite of four iterators for std::vector from the outside of std:
:vector. That is assume std::vector had no iterators; how would iterators
be implemented?

> > I hope this didn't sound rude, I know it must be hard to write a doc
> > for such a complicated library.
>
>Yes, but that usually means the library needs to be simplified ;-)

I have found boost::iterator to be awesome. Using boost::iterator to
build new iterators is actually easier than the docs seem to make it out
to be. It seems like it might be a case of "you can't see the forest
because of the trees."

 ...Duane