R devel - May 2014 - environment question

According to 
:https://stat.ethz.ch/R-manual/R-devel/library/base/html/environment.html

"If |fun| is a function or a formula then |environment(fun)| returns the 
environment associated with that function or formula. If |fun| is |NULL| 
then the current evaluation environment is returned."

 > environment()
<environment: R_GlobalEnv>
 > environment(environment)
<environment: namespace:base>

This makes sense, however I have two questions on things that don't seem 
to make sense:

1.

 > .Internal(environment(NULL))
<environment: base>

Since we are calling from R_GlobalEnv, how can the calling environment 
be base?

2.

In eval.R in library/base/R:

.GlobalEnv <- environment()
parent.frame <- function(n = 1) .Internal(parent.frame(n))
etc.

Since the functions being defined are in base, how can the calling 
environment be R_GlobalEnv. Or does this just set .GlobalEnv temporarily 
to base?

Thanks
Mick Jordan


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On 17 May 2014, at 19:42 , Mick Jordan <mick.jordan at oracle.com> wrote:
> According to 
> :https://stat.ethz.ch/R-manual/R-devel/library/base/html/environment.html
> 
> "If |fun| is a function or a formula then |environment(fun)| returns
the
> environment associated with that function or formula. If |fun| is |NULL| 
> then the current evaluation environment is returned."
> 
>> environment()
> <environment: R_GlobalEnv>
>> environment(environment)
> <environment: namespace:base>
> 
> This makes sense, however I have two questions on things that don't
seem
> to make sense:
> 
> 1.
> 
>> .Internal(environment(NULL))
> <environment: base>
> 
> Since we are calling from R_GlobalEnv, how can the calling environment 
> be base?
Read the Description section in ?.Internal carefully....

Basically, you are calling .Internal from the command line. It is not designed
to be called from there and only wizards know what happens if it is. (The set of
wizards who might know whether it makes any sense at all does not include me!)

> 
> 2.
> 
> In eval.R in library/base/R:
> 
> .GlobalEnv <- environment()
> parent.frame <- function(n = 1) .Internal(parent.frame(n))
> etc.
> 
> Since the functions being defined are in base, how can the calling 
> environment be R_GlobalEnv. Or does this just set .GlobalEnv temporarily 
> to base?
.GlobalEnv is a variable in base alright. The assignment happens when base is
being loaded and _at that point_ the environment is R_GlobalEnv.
> 
> Thanks
> Mick Jordan
> 
> 
> 	[[alternative HTML version deleted]]
> 
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