[Rd] change in behavior of <<-
Thomas Lumley
tlumley at u.washington.edu
Wed Mar 31 16:32:24 CEST 2004
On Tue, 30 Mar 2004, Vincent Carey 525-2265 wrote:
>
> There has been a change to the behavior of <<-.
> See the error thrown at the bottom of the transcript
> below. I don't believe this is an intended change.
It's an unintended side-effect of an intended change. Since we don't use
<<- very much in base R it didn't get noticed.
-thomas
>
> ==========
> older version of R-devel
> ==========
>
> > version
> _
> platform i686-pc-linux-gnu
> arch i686
> os linux-gnu
> system i686, linux-gnu
> status alpha
> major 1
> minor 9.0
> year 2004
> month 03
> day 09
> language R
> > x <<- list()
> > x[["a"]] <<- list()
> > x[["a"]][["b"]] <<- 3
> > x
> $a
> $a$b
> [1] 3
>
> ===========
> more recent version of R-devel:
> ===========
>
> > version
> _
> platform i686-pc-linux-gnu
> arch i686
> os linux-gnu
> system i686, linux-gnu
> status beta
> major 1
> minor 9.0
> year 2004
> month 03
> day 30
> language R
> > x <<- list()
> > x
> list()
> > x[["a"]] <- list()
> > x
> $a
> list()
>
> > x[["a"]] <- 2
> > x
> $a
> [1] 2
>
> > x[["a"]] <<- 2
> Error: Object "x" not found
>
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>
Thomas Lumley Assoc. Professor, Biostatistics
tlumley at u.washington.edu University of Washington, Seattle
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