Re: [R] Concepts question: environment, frame, search path

From: Duncan Murdoch <>
Date: Wed, 02 May 2007 06:56:34 -0400

On 01/05/2007 11:34 AM, Prof Brian Ripley wrote:

> On Tue, 1 May 2007, Duncan Murdoch wrote:

>> On 01/05/2007 12:29 AM, Graham Wideman wrote:
>>> Refman p122:  "Environments consist of a frame, or collection of named
>>> objects, and a pointer to an enclosing environment."
>>> Is the "or" here explaining parenthetically that a frame is a collection of
>>> named objects, or is separating too alternative structures for an
>>> environment?

>> The former.
>>> If the former, does this imply that a frame can contain arbitrary variables?

>> Yes, but a frame isn't an R object, it's a concept that appears in
>> descriptions, e.g. part of an environment, or the local variables
>> created during function evaluation, etc.
>>> And "pointer"? Is that a type of thing in R?

>> No, there are no pointers in R. There are a couple of tricks to fake
>> them (e.g. environment objects aren't copied when assigned, you just get
>> a new reference to the same environment; this allows you to construct
>> something like a pointer by wrapping an object in an environment), but I
>> don't recommend using these routinely.
> Nevertheless, the statement is true. R is implemented using pointers.

Yes, definitely. I misread the original posting, and didn't notice that the "pointer" question was connected to the previous quote.

Duncan Murdoch mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Wed 02 May 2007 - 11:20:39 GMT

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