[Rd] class(<matrix>) |--> c("matrix", "arrary") [was "head.matrix ..."]
murdoch@dunc@n @end|ng |rom gm@||@com
Sun Nov 10 17:48:26 CET 2019
On 10/11/2019 9:17 a.m., Bryan Hanson wrote:
>> On Nov 10, 2019, at 3:36 AM, Martin Maechler <maechler using stat.math.ethz.ch> wrote:
>>>>>>> Gabriel Becker
>>>>>>> on Sat, 2 Nov 2019 12:37:08 -0700 writes:
>>> I agree that we can be careful and narrow and still see a
>>> nice improvement in behavior. While Herve's point is valid
>>> and I understand his frustration, I think staying within
>>> the matrix vs c(matrix, array) space is the right scope
>>> for this work in terms of fiddling with inheritance.
>>>> Also, we seem to have a rule that inherits(x, c) iff c %in% class(x),
>>> good point, and that's why my usage of inherits(.,.) was not
>>> quite to the point. [OTOH, it was to the point, as indeed from
>>> the ?class / ?inherits docu, S3 method dispatch and inherits
>>> must be consistent ]
>>>> which would break -- unless we change class(x) to return the whole
>>> set of inherited classes, which I sense that we'd rather not do....
>>> Note again that both "matrix" and "array" are special [see ?class] as
>>> being of __implicit class__ and I am considering that this
>>> implicit class behavior for these two should be slightly
>>> changed ....
>>> And indeed I think you are right on spot and this would mean
>>> that indeed the implicit class
>>> "matrix" should rather become c("matrix", "array").
>> I've made up my mind (and not been contradicted by my fellow R
>> corers) to try go there for R 4.0.0 next April.
>> I've found the few places in base R that needed a change (to
>> pass 'make check-all' in the R sources) and found that indeed a
>> overzealous check in 'Matrix' needed also a change (a place
>> where the checking code assume class(<matrix>) |--> "matrix" ).
>> There are certainly many more package (codes and checks) that
>> need adaption .. i.e., should be changed rather *before* the
>> above change is activated in R-devel (and then will affect all CRAN
>> and Bioconductor checks.)
>> To this end, I've published an 'R Blog' yesterday,
>> which translates to
>> notably mentioning why using class(x) == "...." (or '!=') or
>> switch(class(.) ...) is quite unsafe and hence bad and you
>> should very often not replace class(x) by class(x) but
>> really use the "only truly correct" ;-)
>> inherits(x, "...")
>> is(x, "....") # if you're advanced/brave enough (:-) to
>> # use formal classes (S4)
> Thanks for the helpful blog post Martin. Is the following
> “test_class” %in% class(some_object)
> which I think in your symbols would be
> “…” %in% class(x)
> safe as far as you see it? By safe, I mean equivalent to your suggestion of inherits(x, “…”) .
Those aren't equivalent if S4 gets involved. You can see it if you run
example("new") # Creates an object named t2 of class "trackcurve"
# that contains "track"
inherits(t2, "track") # TRUE
"track" %in% class(t2) # FALSE
I can't think of any examples not involving S4.
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