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
Builtins have referential semantics in R (like e.g. environments, but
also some other types).
Tomas
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