[Rd] intersect() change of behavior in 4.2

[Lluís Revilla]

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,

Lluís


On Tue, 12 Apr 2022 at 01:22, Gábor Csárdi <csardi.gabor using 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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