ch-ch-changes

[Andrei Alexandrescu]

Denis Koroskin wrote:
> On Wed, 28 Jan 2009 07:15:25 +0300, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> wrote:
> 
>> I've worked valiantly on defining the range infrastructure and making 
>> std.algorithm work with it. I have to say that I'm even more pleased 
>> with the result than I'd ever expected when I started. Ranges and 
>> concepts really make for beautiful code, and I am sure pretty darn 
>> efficient too.
>>
>> There's a lot to sink one's teeth in, but unfortunately the code 
>> hinges on a compiler fix that Walter was kind enough to send me 
>> privately. I did document the work, but the documentation doesn't 
>> really make justice to the extraordinary possibilities that lay ahead 
>> of us. Anyhow, here's a sneak preview into the up-and-coming ranges 
>> and their algorithms.
>>
>> http://ssli.ee.washington.edu/~aalexand/d/web/phobos/std_range.html
>> http://ssli.ee.washington.edu/~aalexand/d/web/phobos/std_algorithm.html
>>
>> Ranges are easy to define and compose efficiently. It was, however, a 
>> pig to get a zip(r1, r2, ...) working that can mutate back the ranges 
>> it iterates on. With that, it's very easy to e.g. sort multiple arrays 
>> in parallel. Similarly, chain(r1, r2, ...) is able to offer e.g. 
>> random iteration if all components offer it, which means that you can 
>> do crazy things like sorting data that sits partially in one array and 
>> partially in another.
>>
>> Singly-linked list ranges are in, and to my soothing I found an answer 
>> to the container/range dichotomy in the form of a topology policy. A 
>> range may or may not be able to modify the topology of the data it's 
>> iterating over; if it can, it's a free-standing range, much like 
>> built-in arrays are. If it can't, it's a limited range tied to a 
>> container (of which I defined none so far, but give me time) and it's 
>> only the container that can mess with the topology in controlled ways. 
>> More on that later.
>>
>> Feedback welcome.
>>
>>
>> Andrei
> 
> Sweet!
> 
> One note - "move" has a precondition: "!pointsTo(source, source)". 
> Shouldn't it be "!pointsTo(source, target)"?

Source must not point to itself because after the move the moved object 
will point to an empty shell. It may point to target because after the 
move the moved object will point to itself.

Andrei