Re: [boost] Re: Boost Iterable Range Library update (v1.5)

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.

Best,
John

-- 
John Torjo,    Contributing editor, C/C++ Users Journal
-- "Win32 GUI Generics" -- generics & GUI do mix, after all
-- http://www.torjo.com/win32gui/
-- v1.5 - tooltips at your fingertips (work for menus too!)
    + bitmap buttons (work for MessageBox too!)
    + tab dialogs, hyper links, lite html