iterator help - C / C++

Rex_chaos

Hi all,
I am writing my own container and need an iterator. I am hesitating
if I should my iterator should inherited from std::iterator or just
write my own one. Please give me an idea.

BTW, if I write my own one, should I let it defined inside my
container(inner class) or just be a complelely independent class.

Thanks.

Jul 19 '05 #1

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2854

David B. Held

"Rex_chaos" <re*******@21cn .com> wrote in message
news:f7******** *************** *@posting.googl e.com...

I am writing my own container and need an iterator. I am
hesitating if I should my iterator should inherited from
std::iterator or just write my own one. Please give me an
idea.
Generally, you write an iterator that is most appropriate for
accessing the data in your container.
BTW, if I write my own one, should I let it defined inside my
container(inner class) or just be a complelely independent
class.

Most STL implementations define the iterator types as
nested classes. I prefer this technique myself, but I don't
believe there is any harm in defining it outside the container
class.

Dave

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Jul 19 '05 #2

Dietmar Kuehl

re*******@21cn. com (Rex_chaos) wrote:

I am writing my own container and need an iterator. I am hesitating
if I should my iterator should inherited from std::iterator or just
write my own one. Please give me an idea.
'std::iterator< >' just typedefs a bunch of types. That's it. If you
don't derive from 'std::iterator< >' you should be sure to [partially]
specialize 'std::iterator_ traits<>' for your iterator type because
otherwise the algorithms won't work OK. Due to lack of partial
specialization support with some compilers, it is probably a good idea
to derive from 'std::iterator< >' anyway: originally, this was mostly a
work around.
BTW, if I write my own one, should I let it defined inside my
container(inner class) or just be a complelely independent class.

This one is a little bit tricky. First of all, it does not matter to
user. Since nested classes have no additional rights external class
have, nesting the iterator class only serves a documentation purpose.
With some specialization I found that it is sufficient to specialize
the container while leaving the iterator alone. Also, the semantics of
making an external class a friend are well defined in the standard
which does not apply to nested classes. Thus, I tend to make iterators
external classes. There is, however, no strong argument I'm aware of
which prefers one of the approaches.
--
<mailto:di***** ******@yahoo.co m> <http://www.dietmar-kuehl.de/>
Phaidros eaSE - Easy Software Engineering: <http://www.phaidros.co m/>

Jul 19 '05 #3

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