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From: John Torjo (john.lists_at_[hidden])
Date: 2004-11-12 14:10:05

> Like Robert I am uncomfortable with a
> range concept that has iteration capabilities.
> For one thing, standard containers don't
> satisfy that concept, and it seems to me
> that a container ought to be a range without
> any special adaptation. Furthermore

Well... This was to allow easy manual loops.

> I have doubts about how well this "range/iterator"
> concept maps onto bidirectional
> and random access. That said...

It maps ok with bidirectional/random access. If an iterator has a given
iterator category, the range will preserve it. I have used it in code,
and it's quite powerful.

> ...Perhaps more importantly, iterator interfaces don't lend themselves
> to functional composition:
> ranges::for_each(
> transformed(filtered(some_array, is_even), _1 / 2)
> , print);
> Try to say *that* with iterators.

Indeed ;)

> This is the design approach taken in
> MPL and Fusion, and it works very well. I am
> strongly for an algorithm and lazy adapter
> library based on ranges, and moderately
> strongly against directly giving ranges any
> direct iteration capability.

As you probably know, the library is around 1 year old. I've used it
heavily on some of my projects, and all I can say is that iteration
capability has helped me much.


John Torjo,    Contributing editor, C/C++ Users Journal
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