Message-ID: <4D12E7A7-015E-44BC-8C93-C3199078B144@gmail.com>
Date: 2012-03-20T23:58:20Z
From: Peter Dalgaard
Subject: Substitute adds id attribute?
In-Reply-To: <CABdHhvEKaDNRDjf-3Rp=b=wvnMO-ZNvk8aLge9-U6K8BkJz4Sg@mail.gmail.com>
On Mar 20, 2012, at 22:31 , Hadley Wickham wrote:
> Hi all,
>
> I can't figure out how to make this problem easily reproducible, but I
> can demonstrate it very simply, so I hoped someone might be able to
> suggest a place to start:
>
>> f <- function(x) substitute(x)
>> f(x)
> x
>> f(mpg)
> mpg
> attr(,"id")
> [1] 11
>
> It works as expected in a clean R session:
>
>> f <- function(x) substitute(x)
>> f(x)
> x
>> f(mpg)
> mpg
>
> but not after the following code
>
> library(devtools)
> install_github("staticdocs")
> library(staticdocs)
> build_package("ggplot2", tempdir())
>
> Any ideas?
>
Well, yes; you can get there more quickly as follows:
> x <- as.name("foo")
> attr(x,"id") <- 7913
> x
foo
attr(,"id")
[1] 7913
> substitute(foo)
foo
attr(,"id")
[1] 7913
I.e. if you ever put an attribute on a symbol, it stays there "forever". The fix is probably to forbid setting attributes on symbols (as we already do for environments and NULL) but I bet that breaks something...
> Thanks,
>
> Hadley
>
> --
> Assistant Professor / Dobelman Family Junior Chair
> Department of Statistics / Rice University
> http://had.co.nz/
>
> ______________________________________________
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--
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk Priv: PDalgd at gmail.com