Re: [Rd] identical() fails to compare isS4(<S4 instance>) to TRUE

From: Martin Morgan <mtmorgan_at_fhcrc.org>
Date: Thu, 04 Oct 2012 14:50:43 -0700

On 10/04/2012 02:23 PM, Duncan Murdoch wrote:
> On 12-10-04 4:57 PM, Martin Morgan wrote:
>>
>> > setClass("A", "integer")
>> > isS4(new("A"))
>> [1] TRUE
>> > identical(isS4(new("A")), TRUE)
>> [1] FALSE
>>
>> > sessionInfo()
>> R Under development (unstable) (2012-10-04 r60876)
>> Platform: x86_64-unknown-linux-gnu (64-bit)
>>
>> locale:
>> [1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
>> [3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
>> [5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
>> [7] LC_PAPER=C LC_NAME=C
>> [9] LC_ADDRESS=C LC_TELEPHONE=C
>> [11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
>>
>> attached base packages:
>> [1] stats graphics grDevices utils datasets methods base
>>
>
> I can confirm this in R-devel, but it doesn't happen in R-patched. In R-devel,
> isS4 is returning a vector marked as LGLSXP, but containing the value 16, not
> the usual 1 for TRUE.
>
> > .Internal(inspect(isS4(new("A"))))
> @4bfbed8 10 LGLSXP g0c1 [] (len=1, tl=0) 16
>
> I'm not going to have time to track this down and fix it.

The bit is set at src/include/Rinternals.h:278

  39103 jmc #define IS_S4_OBJECT(x) ((x)->sxpinfo.gp & S4_OBJECT_MASK)

but it's identical that has changed; it looks as though there are other similar operations in that header and probably elsewhere.

Martin

>
> Duncan Murdoch

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