Re: [boost] Help with iterator helpers

From: nbecker_at_[hidden]
Date: 2002-01-29 11:35:32

>>>>> "David" == David Abrahams <david.abrahams_at_[hidden]> writes:

    David> ----- Original Message -----
    David> From: <nbecker_at_[hidden]>

    >> I was hoping to find a simpler example.  One thing not clear to me is
    >> the first template parameter T.  It says "operand type".  In the
    >> example, it is set to "test_iter<T,R,P>", which is a self-reference.
    >> I'm confused.

    David> The iterator helpers use the same idiom as the rest of the operators library
    David> templates: the first parameter is the type to which you are adding the
    David> operator functionality, i.e. the derived class. Don't worry; it's correct
    David> and it works.

    David> FWIW, most people find the iterator helpers aren't that useful
    David> now that we
    David> have the iterator adaptor library. It does a lot more to
    David> automate the job of
    David> making correct and useful iterators.
    >> 
    >> I'll have a look.  I thought the adaptors were, well, adaptors.  In
    >> this case, I'm not adapting an existing iterator, but making a new
    >> one, so I didn't think that the adaptors were applicable.

    David> You can adapt anything; it doesn't have to be an iterator. Your iterator has
    David> some state data, right? Just adapt that.

Depends what you mean by "adapt".  If by "adapt x" you mean "x is the
first parameter to iterator_adaptor", then I believe x has to be an
iterator.  You can't directly adapt a container, for example.  You can
adapt the container's iterator.

I guess if you want to adapt the container, you have to do it in 2
steps.  First adapt the container's iterator, then make an object that
uses that adapted iterator.