On 14-03-09 1:59 PM, Benjamin Tyner wrote:
Duncan,
Thanks for the explanation and commentary. Starting to make more
sense...so, long story short, it seems the first thing one should check
is whether base imports utils:
> packageDescription("base")
Package: base
Version: 3.0.1
Priority: base
Title: The R Base Package
Author: R Core Team and contributors worldwide
Maintainer: R Core Team <r-c...@r-project.org>
Description: Base R functions
License: Part of R 3.0.1
Built: R 3.0.1; ; 2013-10-16 10:50:56 UTC; unix
-- File: /usr/lib/R/library/base/Meta/package.rds
I'll interpret the lack of an "Imports:" line to mean that base does not
import any packages. So then the next thing to check is the enclosing
environment:
> parent.env(.BaseNamespaceEnv)
<environment: R_GlobalEnv>
Ah-ha! Unlike the base package environment, the base namespace
environment has its enclosing environment already on the search path, so
eventually leads back to utils. (This is the piece of the puzzle
prompting my original question about "... machinery that allows ...")
So hypothetically, if I had attached utils ahead of .GlobalEnv on the
search path, then functions in the base namespace would no longer be
able to see objects in utils? (I realize the answer may be vacuous,
since library() does not honor pos=1).
I suspect in that alternate universe the base namespace would still be
parented by the first entry in the search list.
Duncan Murdoch
Regards,
Ben
On 03/09/2014 09:09 AM, Duncan Murdoch wrote:
On 14-03-08 6:42 PM, Benjamin Tyner wrote:
Duncan,
Thank you for the informative link. So, do the loaded namespaces have an
"ordering" akin to the package search path that determines that
functions in the base namespace can see objects in the utils namespace?
(I noticed that loadedNamespaces() just comes back in alphabetical
order.)
No. The article that Henrik cited gives a reasonable description up
until near the end, where (in my opinion) it makes things
unnecessarily complicated. I'd recommend that you stop reading around
where he tries to explain the dotted lines. In particular, ignore the
second version of the "Map of the World"; the first one is accurate,
the second is just misleading.
In answer to your question: Gupta's article misses the possibility of
packages that are loaded but not in the search path. In the notation
of the first part of that article, loading a namespace just puts it in
the middle two columns (i.e. creates the namespace and imports
environments) without putting it in the search list. That happens
when you import or load a package without attaching it. The search
path imposes an ordering, things that aren't in it aren't ordered.
Duncan Murdoch
Regards
Ben
On 03/07/2014 11:46 AM, Duncan Murdoch wrote:
On 07/03/2014 10:16 AM, Benjamin Tyner wrote:
Hello,
I realize that a function in <environment: base> (for example,
function
"head1" below) is unable to see (without resorting to "::", anyway)
objects in utils (for example, "head" below), since package:base is
after package:utils on the search path.
However, I'm wondering what is the machinery that allows a function in
<environment: namespace:base> (for example, function "head2" below) to
be able to see "head" just fine, without needing to resort to "::".
See Luke Tierney's article in R News,
Name space management for R. Luke Tierney, R News, 3(1):2-6, June 2003
<http://cran.r-project.org/doc/Rnews/Rnews_2003-1.pdf>
There's a link to it from the R help system. Run help.start(), then
look at "Technical papers" in the Miscellaneous Material section.
I believe most of what it says is still current; the only thing I can
see at a glance that is no longer correct is that in those days
namespaces were optional in packages. Now all packages have
namespaces.
Duncan Murdoch
I'm also wondering more generally, why there is a need (practically
speaking) for a distinction between the environment associated with a
package and the environment associated with the namespace.
$ export R_PROFILE=/home/btyner/Rprofile.site
$ cat /home/btyner/Rprofile.site
sys.source("/home/btyner/head1.R", envir = baseenv())
sys.source("/home/btyner/head2.R", envir = .BaseNamespaceEnv)
$ cat /home/btyner/head1.R
head1 <- function(x) head(x)
$ cat /home/btyner/head2.R
head2 <- function(x) head(x)
$ Rscript -e "head1(letters)"
Error in head1(letters) : could not find function "head"
Execution halted
$ Rscript -e "head2(letters)"
[1] "a" "b" "c" "d" "e" "f"
$ Rscript -e "sessionInfo()"
R version 3.0.1 (2013-05-16)
Platform: x86_64-pc-linux-gnu (64-bit)
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=C LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets base
Regards
Ben
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
--
//
--
//
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
