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

[Martin Morgan]

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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