Example of a user-defined forward iterator?

[Brett L. Moore]

Hi,

I have an octree class that I would like to (slowly) migrate to an
STL-like container. I now need to implement two forward iterators for the
class. I would like to use the iterators in the following manner:

octree<GLfloat> ::nodeIterator p;
octree<GLfloat> ::itemIterator q;

for (p=foo.begin(); p!=foo.end();p+ +)
{
// bleh
}
(or something reasonably similar). I have reviewed Stroustrup, but have
found the limited examples difficult to adapt to my need. Can anyone
provide an example of a simple container and its iterator?
Thanks,Brett

[Buster Copley]

Re: Example of a user-defined forward iterator?

Brett L. Moore wrote:[color=blue]
> Hi,
>
> I have an octree class that I would like to (slowly) migrate to an
> STL-like container. I now need to implement two forward iterators for the
> class. I would like to use the iterators in the following manner:
>
> octree<GLfloat> ::nodeIterator p;
> octree<GLfloat> ::itemIterator q;
>
> for (p=foo.begin(); p!=foo.end();p+ +)
> {
> // bleh
> }
> (or something reasonably similar). I have reviewed Stroustrup, but have
> found the limited examples difficult to adapt to my need. Can anyone
> provide an example of a simple container and its iterator?
> Thanks,Brett[/color]

Take a look at boost/iterator_adapto rs.h. If you can't use it directly,
the source code may give you a hint or two.

Good luck,
Buster

[John Harrison]

Re: Example of a user-defined forward iterator?


"Thomas Matthews" <tomatthews@sbc global.net> wrote in message
news:3F12919A.6 090201@sbcgloba l.net...[color=blue]
> Brett L. Moore wrote:[color=green]
> > Hi,
> >
> > I have an octree class that I would like to (slowly) migrate to an
> > STL-like container. I now need to implement two forward iterators for[/color][/color]
the[color=blue][color=green]
> > class. I would like to use the iterators in the following manner:
> >
> > octree<GLfloat> ::nodeIterator p;
> > octree<GLfloat> ::itemIterator q;
> >
> > for (p=foo.begin(); p!=foo.end();p+ +)
> > {
> > // bleh
> > }
> > (or something reasonably similar). I have reviewed Stroustrup, but have
> > found the limited examples difficult to adapt to my need. Can anyone
> > provide an example of a simple container and its iterator?
> > Thanks,Brett[/color]
>
> Many books on the subject say to inherit from std::forward_it erator.
> See the <iterators> header.[/color]

Maybe, but I don't believe there is such a class in the standard. I *think*
it may be been in the original STL implementation but got dropped.

Inheriting from std::iterator is a possibility but not required, I think.
[color=blue]
>
> Also, read:
> Effective C++
> More Effective C++ {two separate books)
> by Scott Meyers
>
> The Standard Template Libary
> by Josuttis[/color]

Especially the latter, I would say.

john

[Glen Low]

Re: Example of a user-defined forward iterator?

> (or something reasonably similar). I have reviewed Stroustrup, but have[color=blue]
> found the limited examples difficult to adapt to my need. Can anyone
> provide an example of a simple container and its iterator?[/color]


The clearest conceptual discussion of forward iterators and containers
I've found was in Stepanov's (the creator of STL) old site:

http://www.sgi.com/tech/stl/

http://www.sgi.com/tech/stl/ForwardContainer.html

http://www.sgi.com/tech/stl/ForwardIterator.html

The definitions may be a little dated since STL got munged into the
C++ Standard Library, but I found the site invaluable when I wanted to
implement my own iterators. It has subtleties like what is
"past-the-end" etc. which you wouldn't otherwise get from just reading
code.