[Rd] s4 methods and base

Prof Brian Ripley ripley at stats.ox.ac.uk
Tue Aug 5 20:05:17 MEST 2003

On Tue, 5 Aug 2003, Marsland, John wrote:

> I'm sure that many people are in the same position as me in that they are
> trying to write packages and code that is vaguely "future proof".
> Would it be possible to get some guidance on how the R-core team see the
> evolution of the "base" package with regard to s4 methods.
> There seem to be quite a lot of inconsistencies between s3 and s4 methods
> and classes currently and this (I'm sure) is only to be expected in a period
> of transition. eg POSIXlt vs POSIXt and POSIXct. And there seem like dozens

Those are S3 classes, and there is nothing transitional about them!
There are no S4 classes in `base R' that I am aware of to be inconsistent.
Are you sure you understand the difference?

> of print methods to convert 

First you need to define S4 classes, and there are currently no moves to 
do that for the statistical modelling software, for example.

> - it's not an enviable task and I'm sure it will
> take time! ... if indeed you do see R being purged of s3 by some point in
> the future.

We are still using S3 classes designed a decade ago, and I expect to be 
still using them in another decade.  I even have S4 versions of some of 
them (e.g. lda, multinom) and no plans to use those in R.

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

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