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

From: Benjamin Tyner <btyner_at_gmail.com>
Date: Fri, 08 Apr 2011 21:48:05 -0400


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?

Thanks,
Ben



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