[phobos] phobos commit, revision 1566

[Steve Schveighoffer]

Arguably, Take should never support back and popBack.  If you have a random access range, why wouldn't you just do r[0..3]?

-Steve




----- Original Message ----
> From: Andrei Alexandrescu <andrei at erdani.com>
> To: Discuss the phobos library for D <phobos at puremagic.com>
> Cc: dsource.org <noreply at dsource.org>
> Sent: Sat, May 29, 2010 9:54:58 AM
> Subject: Re: [phobos] phobos commit, revision 1566
> 
> Typo: "Attenpting" (at least two places)

I think popBack for 
> bidirectional ranges is broken. Consider I have a 
range of 1000 elements and 
> I take 5 of them. Then popBack would have to 
back off 996 elements. That is 
> not what your code is doing, and it would 
not satisfy the complexity 
> requirements of popBack.

Please keep the popBack code only for 
> random-access ranges.


Thanks,

Andrei

On 05/29/2010 
> 08:44 AM, dsource.org 
> wrote:
> phobos commit, revision 1566
>
>
> user: 
> rsinfu
>
> msg:
> Fixed bugzilla 3876: std.range.Take 
> back/popBack methods don't work correctly.
> Thanks to Philippe Sigaud for 
> the proposed solution.  It was helpful.
>
> The former 
> implementation simply used input.back for Take.back.  It didn't work if 
> input.length was larger than maxAvailable.  For example:
>  
>   input = [ 1, 2, 3, 4, 5 ]
>    s = take(input, 3)  
>           // [ 1, 2, 3 ]
>    s.back == 
> input.back == 5     // wrong!
>
> Take must pop all the 
> excess elements from the input ([4,5] in the above example) to provide correct 
> back element.  This change makes it to do so if input is purely 
> bidirectional.  (random access is used instead if 
> possible.)
>
> - Added Take.opSlice
> - Added some enforcement 
> error messages
>
> 
> http://www.dsource.org/projects/phobos/changeset/1566
>
> 
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