[phobos] length implementation for Range

[Masahiro Nakagawa]

Thanks for your advice.

changeset 1495 isn't bug fixing, so I listed the summery at the WHATSNEW  
section.


On Wed, 05 May 2010 08:17:11 +0900, Brad Roberts <braddr at puremagic.com>  
wrote:

> Don't forget to update the changelog, noting the issue number if there is
> one.  They're located in the phobos project.
>
> On Wed, 5 May 2010, Masahiro Nakagawa wrote:
>
>> Date: Wed, 05 May 2010 07:06:56 +0900
>> From: Masahiro Nakagawa <repeatedly at gmail.com>
>> Reply-To: Discuss the phobos library for D <phobos at puremagic.com>
>> To: Discuss the phobos library for D <phobos at puremagic.com>
>> Subject: Re: [phobos] length implementation for Range
>>
>> http://www.dsource.org/projects/phobos/changeset/1495
>> Committed.
>>
>>
>> On Wed, 05 May 2010 06:32:46 +0900, Andrei Alexandrescu  
>> <andrei at erdani.com>
>> wrote:
>>
>> > It is a bug, if you could fix that would be great. There are many  
>> places in
>> > which we don't use @property but we must.
>> >
>> > Andrei
>> >
>> > Masahiro Nakagawa wrote:
>> > > I agree. But, length of some range objects in Phobos isn't a  
>> property.
>> > > Is this a bug? If so, I will commit.
>> > >  On Wed, 05 May 2010 04:28:06 +0900, Andrei Alexandrescu
>> > > <andrei at erdani.com> wrote:
>> > >
>> > > > I think the length should be a property.
>> > > >
>> > > > Andrei
>> > > >
>> > > > Masahiro Nakagawa wrote:
>> > > > > Hi list,
>> > > > > This post is my first post at Phobos ML :)
>> > > > > I have one question about hasLength.
>> > > > > Current implementation from std.range:
>> > > > > -----
>> > > > > template hasLength(R)
>> > > > > {
>> > > > >      enum bool hasLength = is(typeof(R.init.length) : ulong) &&
>> > > > >          !isNarrowString!R;
>> > > > > }
>> > > > > -----
>> > > > > This implementation has following issues.
>> > > > > http://d.puremagic.com/issues/show_bug.cgi?id=2873
>> > > > > http://d.puremagic.com/issues/show_bug.cgi?id=3508
>> > > > > But, hasLength returns true when length method is marked as  
>> @property.
>> > > > > We should fix the above issue or length method should be marked  
>> as
>> > > > > @property?
>> > > > > If latter, some ranges in phobos are incomplete.