[Rd] sort yields different results on OS X (PR#14163)

[Prof Brian Ripley]

On Tue, 22 Dec 2009, Peter Dalgaard wrote:

> Prof Brian Ripley wrote:
>
>> 
>> That different OSes use the same name for a locale does not make them the 
>> same locale.
>> 
>> Note that R can be compiled to use ICU, which provides a well-considered 
>> collation suite.  R on Mac OS X uses ICU, as does a Linux build if it is 
>> available -- so I would say that it is RHEL that is out of line here (it 
>> makes little sense to have < and > far apart in the collation sequence).
>> 
>
> That's not it:
>
>> v <- c("1","<0","<3","2")
>> sort(v)
> [1] "<0" "1"  "2"  "<3"
>
> The point is rather that "special characters" are ignored during collation.

Sometimes ....

> Apparently, this comes from /usr/share/i18n/locales/iso14651_t1_common on 
> Fedora; I wouldn't know how faithful to the ISO standard that is.

ISO 14651 is a version of the Unicode Collation Algorithm 
(http://www.unicode.org/reports/tr10/) which ICU uses.  So other 
people have implemented the same set of rules to give different 
results -- which is quite possible given the number of non-prescribed 
choices that need to be made.

We've seen too many anomalies from glibc to trust it: which is why ICU 
is used if available.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595