From berwin at maths.uwa.edu.au  Thu Mar 12 08:46:16 2009
From: berwin at maths.uwa.edu.au (Berwin A Turlach)
Date: Thu, 12 Mar 2009 15:46:16 +0800
Subject: [Rd] surprising behaviour of names<-
In-Reply-To: <49B8110A.5060909@idi.ntnu.no>
References: <49B67CB1.8060005@idi.ntnu.no> <49B682F9.8050307@biostat.ku.dk>
	<49B6E6D9.7010809@idi.ntnu.no>
	<96A4BB14-D6EA-44B1-B524-6DB139F3A7F8@r-project.org>
	<49B8110A.5060909@idi.ntnu.no>
Message-ID: <20090312154616.5b650ce2@berwin-nus1>

On Wed, 11 Mar 2009 20:29:14 +0100
Wacek Kusnierczyk <Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:

> Simon Urbanek wrote:
> > Wacek,
> >
> > Peter gave you a full answer explaining it very well. If you really
> > want to be able to trace each instance yourself, you have to learn
> > far more about R internals than you apparently know (and Peter
> > hinted at that). Internally x=1 an x=c(1) are slightly different in
> > that the former has NAMED(x) = 2 whereas the latter has NAMED(x) =
> > 0 which is what causes the difference in behavior as Peter
> > explained. The reason is that c(1) creates a copy of the 1 (which
> > is a constant [=unmutable] thus requiring a copy) and the new copy
> > has no other references and thus can be modified and hence NAMED(x)
> > = 0.
> 
> 
> simon, thanks for the explanation, it's now as clear as i might
> expect.
> 
> now i'm concerned with what you say:  that to understand something
> visible to the user one needs to "learn far more about R internals
> than one apparently knows".  your response suggests that to use r
> without confusion one needs to know the internals, 

Simon can probably speak for himself, but according to my reading he
has not suggested anything similar to what you suggest he suggested. :)

> and this would be a really bad thing to say.. 

No problems, since he did not say anything vaguely similar to what you
suggest he said.

Cheers,

	Berwin



[Rd] surprising behaviour of names<-
Berwin A Turlach