[Rd] BUG?: A copy of base::`+` (primitive) is not a clone but a "pointer"

[Benjamin Tyner]

For what it's worth, the current behavior seems to have begun starting 
with version 3.6.0. If I run in version 3.5.3:

 > p1 <- .Primitive('+') ; p2 <- p1 ; attr(p1, "myattr") <- 1 ; p2
function (e1, e2)  .Primitive("+")


> On 11/18/19 10:45 AM, Martin Maechler wrote:
> >>>>>>/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. /
> I think internal objects such as builtins should never be modified by
> user code in the first place. We had to add detection for modifications
> of NIL and symbols in the past, maybe we will have to do it for builtins
> as well.
>
> Environments can be used in user code as objects with referential
> semantics, e.g. to keep mutable state.
>
> Tomas
> >//>/Martin /