[R] best practice(s) for retrieving a local variable from a closure

Gabor Grothendieck ggrothendieck at gmail.com
Sat Apr 9 03:55:33 CEST 2011

On Fri, Apr 8, 2011 at 9:48 PM, Benjamin Tyner <btyner at gmail.com> wrote:
> Greetings,
> Say I have defined
>  mp <- function(a) function(x) x^a
>  f2 <- mp(2)
> and I would like to retrieve the "a" which is local to f2. Two options come
> to mind;
>  get("a", envir=environment(f2))
>  eval(substitute(a), environment(f2))
> I'm curious if one of these is preferred over the other in terms of
> efficiency, robustness, aesthetics, etc. Or perhaps someone can share
> another way to skin this cat, besides wrappers around eval() like
>  evalq(a, environment(f2))
>  with(environment(f2), a)
> Also, I'd like to confirm that I have used the correct terminology in the
> subject line, that "a" is a local variable with respect to f2, which is a
> closure?

Solutions involving eval tend to be less preferred.  "a" is termed a
free variable of f2.

Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

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