>>>>> Ivan Krylov
>>>>> on Thu, 14 Mar 2024 14:17:38 +0300 writes:
> On Thu, 14 Mar 2024 10:41:54 +0100
> Martin Maechler <maech...@stat.math.ethz.ch> wrote:
>> Anybody trying S7 examples and see if they work w/o producing
>> wrong warnings?
> It looks like this is not applicable to S7. If I overwrite
> as.data.frame with a newly created S7 generic, it fails to dispatch on
> existing S3 classes:
> new_generic('as.data.frame', 'x')(factor(1))
> # Error: Can't find method for `as.data.frame(S3<factor>)`.
> But there is no need to overwrite the generic, because S7 classes
> should work with existing S3 generics:
> foo <- new_class('foo', parent = class_double)
> method(as.data.frame, foo) <- function(x) structure(
> # this is probably not generally correct
> list(x),
> names = deparse1(substitute(x)),
> row.names = seq_len(length(x)),
> class = 'data.frame'
> )
> str(as.data.frame(foo(pi)))
> # 'data.frame': 1 obs. of 1 variable:
> # $ x: <foo> num 3.14
> So I think that is nothing to break because S7 methods for
> as.data.frame will rely on S3 for dispatch.
Yes, as it should be. Thank you for checking..
>> > The patch passes make check-devel, but I'm not sure how to safely
>> > put setGeneric('as.data.frame'); as.data.frame(factor(1:10)) in a
>> > regression test.
>>
>> {What's the danger/problem? we do have "similar" tests in both
>> src/library/methods/tests/*.R
>> tests/reg-S4.R
>>
>> -- maybe we can discuss bi-laterally (or here, as you prefer)
>> }
> This might be educational for other people wanting to add a regression
> test to their patch. I see that tests/reg-tests-1e.R is already running
> under options(warn = 2), so if I add the following near line 750
> ("Deprecation of *direct* calls to as.data.frame.<someVector>")...
> # Should not warn for a call from a derivedDefaultMethod to the raw
> # S3 method -- implementation detail of S4 dispatch
> setGeneric('as.data.frame')
> as.data.frame(factor(1))
> ...then as.data.frame will remain an S4 generic. Should the test then
> rm(as.data.frame) and keep going? (Or even keep the S4 generic?) Is
> there any hidden state I may be breaking for the rest of the test this
> way?
> The test does pass like this, so this may be worrying about nothing.
Indeed, this could be educational; I think just adding
removeGeneric('as.data.frame')
is appropriate here as it is self-explaining and should not leave
much traces.
I'm about to test this in reg-tests-1e.R and with make check-all
and commit later today,
thanking you, Ivan!
Martin
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