On Wed, 7 Jun 2006, Martin Maechler wrote:
> {Diverted to R-devel}
>
>>>>>> "BDR" == Prof Brian Ripley <[EMAIL PROTECTED]>
>>>>>> on Tue, 6 Jun 2006 21:14:01 +0100 (BST) writes:
>
> BDR> On Tue, 6 Jun 2006, [EMAIL PROTECTED]
> BDR> wrote:
> >> Hi ,
> >>
> >> When I sort a vector of POSIXct values in R-2.3.0 and
> >> R-2.3.1, I get a vector of numeric values and this gets
> >> some of my code to crash (class object creation). Is that
> >> a R bug?
>
> BDR> No, it is as documented: see ?sort
>
> BDR> As from R 2.3.0, all attributes are removed from
> BDR> the return value except names, which are sorted. (If
> BDR> 'partial' is specified even the names are removed.)
>
> BDR> Note, the class is an attribute. For many classes
> BDR> sorting destroys the appropriateness of the class.
(An example BTW is a time series: the times associated with values would
be shuffled on sorting.)
> Indeed, and I agree this a good change.
> However, the above also suggests that ideally, sort() would be
> a generic function.
>
> One good reason for sort() not being generic now is the fact
> that method dispatch costs a bit, *and* that we like sort() to
> be really fast.
> One way to achieve a generic sort() and keep the possibility of
> of very fast sort() --- similarly to rep() and rep.int()
> would be to rename the current sort into something like
> sortNum() {"Num" for numeric}, make sort() into a generic,
> and replace sort() by sortNum() in those code parts which need
> to remain optimally fast.
The current sort handles much more than numeric vectors. I agree with
reasoning, but it seems wrong to ask all those using sort() in packages
to rename their usages (conditional on R >= 2.4.0) not to be penalized.
sort() is an interface to three C functions. It ought to be possible to
use internal dispatch for internal sort and (not for psort or qsort), for
which I believe the overhead would be acceptable. I think that is
acceptable: people who set partial or method must have read the help page.
--
Brian D. Ripley, [EMAIL PROTECTED]
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
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