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From: Arno Schödl (aschoedl_at_[hidden])
Date: 2008-09-02 17:39:51

> I'm trying to find out what the specific example applications are. I
> have a suspicion that range adapters or single-level iterator adaptors
> may not be the best way to address these applications and may even
> sacrifice significant performance, but I can't tell until I know what
> the applications are. Just so, single-level iterators (or ordinary
> range adapters, which don't add anything conceptually to iterators) are
> not the best way to address iteration over hierarchical data structures,
> which is why we have segmented iterators.

This is a typical one, copied straight from our code:

                                                make_first_range( vecpairanchorsrcgrdln ),
                                                boost::mem_fn(&_vector< Ref<CGridlineAnchor> >::begin)
                                        boost::mem_fn( &CGridlineAnchor::Binding )

This is a case in point: I did not write this code, and in the absence of specific guidelines against, the programmer decided to stack transform_range. In this case, performance-wise, this is no better or worse than using a single transform_range with boost::bind. Likewise, people may innocently write

rng | filtered( funcA )
    | filtered( funcB )
    | filtered( funcC )
    | filtered( funcD )
    | filtered( funcE )

blissfully unaware of any performance penalty.

> However, it seems to me that you already have a general answer in mind,
> and it might be better to back up and look at the real problems you want
> to solve before moving on to the answer.

Would it be my turn now to ask for some credit ;-) ?


Dr. Arno Schoedl · aschoedl_at_[hidden] 
Technical Director 
think-cell Software GmbH · Invalidenstr. 34 · 10115 Berlin, Germany · phone +49-30-666473-10 · toll-free (US) +1-800-891-8091
Directors: Dr. Markus Hannebauer, Dr. Arno Schoedl · Amtsgericht Charlottenburg, HRB 85229

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