[Rd] %in% very slow for Date class since R 4.3

[Martin Maechler]

>>>>> Enrico Schumann 
>>>>>     on Fri, 27 Jun 2025 15:42:47 +0200 writes:

    > On Thu, 26 Jun 2025, Dirk Eddelbuettel writes:
    >> On 25 June 2025 at 07:11, Kurt Hornik wrote:
    >> | >>>>> hormutz screed writes:
    >> | 
    >> | Thanks.  Makes sense to me, needs some discussion in R Core ...
    >> 
    >> Nice to see this in NEWS [1]:
    >> 
    >> CHANGES IN R-devel BUG FIXES
    >> 
    >> ‘<Date> %in% set’ has become as fast again, as it was before R 4.3.0, via
    >> new S3 method ‘mtfrm.Date’. 
    >> 
    >> Dirk
    >> 
    >> [1] https://developer.r-project.org/blosxom.cgi/R-devel via the RSS feed

    > As a remark -- not a complaint ;-) --, in R 4.5.1: 

[ well, I think you "should complain",  read on .... ]

Yes, we've realized that almost immediately,
and between the events and excellent talks at "Peter's 60th
birthday" workshop *), I have addressed this problem
and will commit changes (to C code) to solve it now within a few
hours hopefully:

We do want to keep the "equality" of  `==` (and hence `!=` )
equivalent to that of match() {and hence `%in%`} for such basic objects,

and indeed, we have always (I think) had

  R> "2025-01-01" == as.Date("2025-01-01")
  [1] TRUE


Thank you still, Enrico, for raising the issue!
Martin


--
Martin Maechler
ETH Zurich  and  R Core team

*) https://math.ethz.ch/fim/activities/conferences/High-dimensional-statistics-applications-and-distributional-shifts


    > match("2025-01-01", as.Date("2025-01-01"))
    > ## [1] 1

    > which is, in a way, consistent with

    > "2025-01-01" == as.Date("2025-01-01")
    > ## [1] TRUE


    > In R-devel (2025-06-26 r88362):

    > match("2025-01-01", as.Date("2025-01-01"))
    > ## [1] NA

    > "2025-01-01" == as.Date("2025-01-01")
    > ## [1] TRUE


    > -- 
    > Enrico Schumann
    > Lucerne, Switzerland
    > https://enricoschumann.net