'modifyList' drops (not adds) NULL components

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'."),

and also with how I'd want the function to behave.

foo <- modifyList(x=list(A=1), val=list(B=NULL, C=3))
foo$B

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.

-----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

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.