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]

Brett L. Moore wrote:

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

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

Good luck,
Buster

[John Harrison]

"Thomas Matthews" <to********@sbcglobal.net> wrote in message
news:3F**************@sbcglobal.net...

Brett L. Moore wrote:

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
Many books on the subject say to inherit from std::forward_iterator.
See the <iterators> header.

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.

Also, read:
Effective C++
More Effective C++ {two separate books)
by Scott Meyers

The Standard Template Libary
by Josuttis

Especially the latter, I would say.

john

[Glen Low]

> (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?

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.