R devel - Jul 2010 - Creating an environment with attributes in a package

Dear all,

I am trying to create an environment object with additional attributes, viz.

Foo <- structure(new.env(), name="Foo")

Doing this in a standard session works fine: I get the environment
with attr(,"name") set as expected. But if the same code appears
inside a package source file, I get just the plain environment with no
attributes set. Using a non-environment object works as I would expect
within the package (i.e. the attributes remain).

I've looked through the documentation for reasons for this, and the
only thing I've found is the mention in the language definition that
"assigning attributes to an environment can lead to surprises".
I'm
not sure if this is one of the surprises that the author(s) had in
mind! Could someone tell me whether this is expected, please?

All the best,
Jon

--
Jonathan D Clayden, PhD
Lecturer in Neuroimaging and Biophysics
Radiology and Physics Unit
UCL Institute of Child Health
30 Guilford Street
LONDON  WC1N 1EH
United Kingdom

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On Fri, Jul 16, 2010 at 8:08 AM, Jon Clayden <jon.clayden at gmail.com>
wrote:
> Dear all,
>
> I am trying to create an environment object with additional attributes,
viz.
>
> Foo <- structure(new.env(), name="Foo")
>
> Doing this in a standard session works fine: I get the environment
> with attr(,"name") set as expected. But if the same code appears
> inside a package source file, I get just the plain environment with no
> attributes set. Using a non-environment object works as I would expect
> within the package (i.e. the attributes remain).
>
> I've looked through the documentation for reasons for this, and the
> only thing I've found is the mention in the language definition that
> "assigning attributes to an environment can lead to surprises".
I'm
> not sure if this is one of the surprises that the author(s) had in
> mind! Could someone tell me whether this is expected, please?
>
> All the best,
> Jon
I had documented a few problems I found in R here:

   http://r-proto.googlecode.com

and you might want to go over them.  The item you mention is discussed
in #1 there.  This was written some time ago and there may have been
relevant changes to R since then so it would be a good idea to double
check everything with the current version of R.

On Fri, Jul 16, 2010 at 2:08 PM, Jon Clayden <jon.clayden at gmail.com>
wrote:
> Dear all,
>
> I am trying to create an environment object with additional attributes,
viz.
>
> Foo <- structure(new.env(), name="Foo")
>
> Doing this in a standard session works fine: I get the environment
> with attr(,"name") set as expected. But if the same code appears
> inside a package source file, I get just the plain environment with no
> attributes set. Using a non-environment object works as I would expect
> within the package (i.e. the attributes remain).
>
> I've looked through the documentation for reasons for this, and the
> only thing I've found is the mention in the language definition that
> "assigning attributes to an environment can lead to surprises".
I'm
> not sure if this is one of the surprises that the author(s) had in
> mind! Could someone tell me whether this is expected, please?
You'll be much less surprised if you do:

Foo <- structure(list(new.env()), name="Foo")

Attributes on reference objects are also passed by reference, and
surprises will result.

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/