Re: [boost] Comment on string / unicode discussion

From: David Abrahams (dave_at_[hidden])
Date: 2006-07-06 06:46:58

"Robert Ramey" <ramey_at_[hidden]> writes:

> David Abrahams wrote:
>> "Robert Ramey" <ramey_at_[hidden]> writes:
>>
>>
>> How are these different from many of the iterators provided by
>> http://www.boost.org/libs/iterator, particularly transform_iterator?
>
> http://www.boost.org/libs/serialization/doc/index.html describes this.
>
> All the "dataflow iterators" are derived from boost.iterator.  For
> some I derived from transform iterator for others I derived
> from filter and I forget the rest.

I don't know what you mean by "derived" but if you're referring to
regular C++ derivation, that generally doesn't result in a legal
iterator class.  For example, the result type of operator++ is usually
wrong.

> Aside from implementing the transforming behavior required
> for the specific instance, the only real addition is the
> requirement that all of them have a templated constructor.

Details would be helpful here.

> This simple addition made all the difference for me.
>
> This permitted me to compose them to any ressonable
> depth and sequence with just one (rather long)
> typedef into a new iterator which can be used
> just as easily as any other.

The existing iterator adaptors are easily composed, so I'd like to
know a little more about what you did, and gained.

> I've never been able to convince anyone else
> of the merit of the approach - but hope springs eternal.

Maybe you never articulated sufficiently clearly what you added to the
basics provided by the iterator library, and why.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com