>>>>> Tomas Kalibera
>>>>> on Mon, 18 Nov 2019 09:36:14 +0100 writes:
> On 11/18/19 9:18 AM, Martin Maechler wrote:
>>>>>>> Henrik Bengtsson
>>>>>>> on Sun, 17 Nov 2019 14:31:07 -0800 writes:
>> > $ R --vanilla R version 3.6.1 (2019-07-05) -- "Action of
>> > the Toes" Copyright (C) 2019 The R Foundation for
>> > Statistical Computing Platform: x86_64-pc-linux-gnu
>> > (64-bit) ...
>>
>> >> str(base::`+`)
>> > function (e1, e2)
>>
>> >> plus <- structure(base::`+`, class = "plus") str(plus)
>> > function (e1, e2) - attr(*, "class")= chr "plus"
>>
>> > ## Hmm ...
>> >> str(base::`+`)
>> > function (e1, e2) - attr(*, "class")= chr "plus"
>>
>> >> class(base::`+`) <- NULL str(base::`+`)
>> > function (e1, e2)
>>
>> > ## Hmm ...
>> >> str(plus)
>> > function (e1, e2)
>>
>> > Even without assigning to `plus`, you get this behavior:
>>
>> > $ R --vanilla
>> >> structure(base::`+`, class = "plus")
>> > function (e1, e2) .Primitive("+") attr(,"class") [1]
>> > "plus"
>>
>> > # Hmm...
>> >> str(base::`+`)
>> > function (e1, e2) - attr(*, "class")= chr "plus"
>>
>> > Looks to be the case for common (all?) .Primitive
>> > functions.
>>
>> No need for 'base::' (who would be crazy enough to redefine `+`?)
>> nor str() actually:
>>
>> attr(`+`, "class") <- NULL # (reset)
>> `+`
>> structure(`+`, class = "plus")
>> `+`
>>
>> is clearly convincing and minimal
>>
>>> attr(`+`, "class") <- NULL
>>> `+`
>> function (e1, e2) .Primitive("+")
>>> structure(`+`, class = "plus")
>> function (e1, e2) .Primitive("+")
>> attr(,"class")
>> [1] "plus"
>>> `+`
>> function (e1, e2) .Primitive("+")
>> attr(,"class")
>> [1] "plus"
>> ---------------------------------------------------------
>>
>> > Is this expected?
>>
>> no. (at least not by 99.999% of R users)
>>
>>
>> > Should I report this one to Bugzilla?
>> yes, please.
>>
>> > /Henrik
> A shorter example is
>> p1 <- .Primitive('+') ; p2 <- p1 ; attr(p1, "myattr") <- 1 ; p2
> function (e1, e2) .Primitive("+")
> attr(,"myattr")
> [1] 1
beautiful ; thank you, Tomas !
> Builtins have referential semantics in R (like e.g. environments, but
> also some other types).
> Tomas
[aarh.. I knew it ... but am showing my age: I had forgotten about it.]
I forget (and don't have time just now to find out) where we
have documented it; it may be good to document also in official
user exposed places such say the ?.Primitive help page.
Martin
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