On 11/16/2009 12:07 PM, Robert Gentleman wrote:
Hi,
On Fri, Nov 13, 2009 at 4:55 PM, Duncan Murdoch <murd...@stats.uwo.ca> wrote:
On 13/11/2009 7:26 PM, Gabor Grothendieck wrote:
On Fri, Nov 13, 2009 at 7:21 PM, Duncan Murdoch <murd...@stats.uwo.ca>
wrote:
On 13/11/2009 6:39 PM, Gabor Grothendieck wrote:
Note that one should use inherits = FALSE argument on get and exists
to avoid returning objects from the parent, the parent of the parent,
etc.
I disagree. Normally you would want to receive those objects. If you
didn't, why didn't you set the parent of the environment to emptyenv()
when
you created it?
$ does not look into the parent so if you are trying to get those
semantics you must use inherits = FALSE.
Whoops, yes. That's another complaint about $ on environments.
That was an intentional choice. AFAIR neither $ nor [[ on
environments was not meant to mimic get, but rather to work on the
current environment as if it were a hash-like object. One can always
get the inherits semantics by simple programming, but under the model
you seem to be suggesting, preventing such behavior when you don't own
the environments in question is problematic.
Sure, I agree with how you did that; I'm not sure you had any choice at
the time (didn't all environments have base as a parent then?). Even
now, you do want both inherits=TRUE and inherits=FALSE behaviour in
different circumstances, and $ has to pick just one. Probably my
wording should have been "That's another gotcha about $ on environments."
Duncan Murdoch
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