[Rd] 'modifyList' drops (not adds) NULL components

[Raubertas, Richard]

See response inline below.

> -----Original Message-----
> From: Deepayan Sarkar [mailto:deepayan.sarkar at gmail.com]
> Sent: Friday, June 28, 2013 7:17 AM
> To: Raubertas, Richard
> Cc: R-devel at r-project.org
> Subject: Re: [Rd] 'modifyList' drops (not adds) NULL components
> 
> On Thu, Jun 27, 2013 at 10:59 PM, Raubertas, Richard
> <richard_raubertas at merck.com> wrote:
> > Dear list,
> >
> > Utils::modifyList() drops NULL components in its second argument, instead
> of adding them to the first argument.  Compare:
> >> modifyList(x=list(A=1), val=list(B=2, C=3))
> > $A
> > [1] 1
> >
> > $B
> > [1] 2
> >
> > $C
> > [1] 3
> >
> >> modifyList(x=list(A=1), val=list(B=NULL, C=3))
> > $A
> > [1] 1
> >
> > $C
> > [1] 3
> >
> > To me this seems inconsistent with the documentation ("Elements in 'val'
> which are missing from 'x' are added to 'x'."),
> 
> Agreed.
> 
> > and also with how I'd want the function to behave.
> 
> Note that you still get
> 
> > foo <- modifyList(x=list(A=1), val=list(B=NULL, C=3))
> > foo$B
> NULL
> 
> So is there a specific reason you want the NULL elements to be
> explicitly listed?
> 
> -Deepayan

Yes, definitely.  Although 'foo$B' gives the same result, 'length(foo)' or 'names(foo)' do not.  Basically, the object 'foo', considered as a whole, is very different in the two cases, and this was a problem in the code I was writing.

Richard
> 
> >
> >> sessionInfo()
> > R version 3.0.1 Patched (2013-06-16 r62969)
> > Platform: x86_64-w64-mingw32/x64 (64-bit)
> >
> > locale:
> > [1] LC_COLLATE=English_United States.1252
> > [2] LC_CTYPE=English_United States.1252
> > [3] LC_MONETARY=English_United States.1252
> > [4] LC_NUMERIC=C
> > [5] LC_TIME=English_United States.1252
> >
> > attached base packages:
> > [1] stats     graphics  grDevices utils     datasets  methods   base
> >
> >
> > Richard Raubertas
> > Merck & Co.
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