R devel - Apr 2022 - intersect() change of behavior in 4.2

I wonder if this change is intentional, and if it is, whether it is
worth mentioning in the NEWS.

? R-4.1 -q -e 'intersect(list(),
"foo")'
> intersect(list(), "foo")
character(0)

? R-4.2 -q -e 'intersect(list(),
"foo")'
> intersect(list(), "foo")
list()

Hi all,

This change is documented on the man page so I think it is
intentional.
>From https://search.r-project.org/R/refmans/base/html/sets.html:
    For union, a vector of a common mode.
    For intersect, a vector of a common mode, or NULL if x or y is NULL.
    For setdiff, a vector of the same mode as x.

Now the results are symmetrical to intersect( "foo", list())
Probably it is worth mentioning in the NEWS as it was found to cause
some test to fail on a Bioconductor package some months ago.
This could affect other packages and analysis too.

Best,

Llu?s


On Tue, 12 Apr 2022 at 01:22, G?bor Cs?rdi <csardi.gabor at gmail.com>
wrote:
>
> I wonder if this change is intentional, and if it is, whether it is
> worth mentioning in the NEWS.
>
> ? R-4.1 -q -e 'intersect(list(), "foo")'
> > intersect(list(), "foo")
> character(0)
>
> ? R-4.2 -q -e 'intersect(list(), "foo")'
> > intersect(list(), "foo")
> list()
>
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