From murdoch at stats.uwo.ca  Wed Mar 25 19:41:00 2009
From: murdoch at stats.uwo.ca (Duncan Murdoch)
Date: Wed, 25 Mar 2009 14:41:00 -0400
Subject: [Rd] linking environments
In-Reply-To: <OF2D459B18.6AF836C2-ONC1257584.0055D84D-C1257584.0056C217@dza.de>
References: <OF2D459B18.6AF836C2-ONC1257584.0055D84D-C1257584.0056C217@dza.de>
Message-ID: <49CA7ABC.3080307@stats.uwo.ca>

On 3/25/2009 11:47 AM, Joerg Betzin wrote:
> Dear R-helpers,
> 
> I try to use nested R-functions as follows:

You didn't use nested functions.  They would look like this:

  help1 <- function(){
      help2 <- function(){
          if (x == 1)
                  cat("Hello world x = 1")
      }

      x <- 1
      help2()
  }

Because help2 is now nested within help1, it can see all the local 
variables in help1, so things work with it done this way.

There are tricks to define help2 outside of help1 but allow it to see 
the variables within there, but I'd keep it simple and avoid them.

Duncan Murdoch

> 
> help1 = function(){
>         x = 1
>         help2()
> }
> 
> with
> 
> help2 = function(){
>         if (x == 1)
>                 cat("Hello world x = 1")
> }
> 
> If I compile these functions and run help1()
> an error message occurs
>         Fehler in help2() : objekt "x" nicht gefunden
> 
> in english "error in help2(): object "x" not found"
> 
> If I change help1 to
> 
> help1 = function(){
>         x <<- 1
>         help2()
> }
> 
> so that "x" is now defined at the global environment it works fine.
> But the problem is, now "x" is defined also outside of help1 and this is 
> not desired !
> 
> Is there any usable solution for this problem?
> But, the original problem is to assign new values for "x" in help1 inside 
> help2 !
> 
> Thanks in advance
>  
> J?rg Betzin
> ---------------------------------------------------
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> 12101 Berlin
> Tel. (030) 260740-20
> E-Mail: joerg.betzin at dza.de
> URL: http://www.dza.de
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[Rd] linking environments
Duncan Murdoch