R devel - Nov 2019 - BUG?: A copy of base::`+` (primitive) is not a clone but a "pointer"

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

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 /

>>>>> Benjamin Tyner 
>>>>>     on Mon, 25 Nov 2019 22:34:33 -0500 writes:
    > 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("+")

No.  What changed was just the *printing* !
(still in R 3.5.x) :
> p1 <- .Primitive('+') ; p2 <- p1 ; attr(p1,
"myattr") <- pi ; attributes(p2)
$myattr
[1] 3.141593
>