[R] Can we get rid of && and ||?
Prof Brian Ripley
ripley at stats.ox.ac.uk
Thu Apr 13 14:38:09 CEST 2000
> Date: Thu, 13 Apr 2000 14:21:14 +0200 (CEST)
> From: GB <gb at stat.umu.se>
> thanks for your comments. I have only one question/remark:
> > > Provided there are no other differences, I suggest that either
> > >
> > > a) '&&' is made obsolete, and '&' is 'improved' so that b in
> > > 'a & b' is evaluated only if some component of a is TRUE, or
> > That would break S compatibility and a lot of correctly written code
> > (including in R itself).
> I meant keeping '&&' for precisely that reason, but changing '&' as
Ah, that's not what I understood by `made obselete'.
(`obsolete' = `disused', `discarded', ..., Concise Oxford Dictionary.)
> indicated, so that new code never had to consider '&&'. So, I made two
> assumptions here: (i) Old code (or S code) will not be disturbed by the
> 'improvement' of '&'; (ii) New code can always use '&' instead of '&&'.
Strictly (i) is false. Suppose I wrote
changed <- x[(n1 <- new(some)) | (n2 <- new(someother))]
Obscure, but legal S code. If n1 is all true, n2 would not be created,
> Of course, if either assumption is wrong, the idea is not so good.
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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