R devel - Feb 2007 - question on docs for delayedAssign and substitute

The help files for delayedAssign and substitute both say that 
substitute() can be used to see the expression associated with a 
promise.  However, I can't see how to do that.  When I try the example 
in help file for delayedAssign I don't see substitute() extracting the 
promise, e.g.:

 > msg <- "old"
 > delayedAssign("x", msg)
 > msg <- "new!"
 > substitute(x) #- I would expect to see 'msg' here
x
 > x #- new!
[1] "new!"
 > substitute(x)
x
 >

Has this functionality been removed, and the docs not updated?  Or am I 
missing something?

-- Tony Plate

 > sessionInfo()
R version 2.4.1 (2006-12-18)
i386-pc-mingw32

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United 
States.1252;LC_MONETARY=English_United 
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] "stats"     "graphics"  "grDevices"
"utils"     "datasets"  "methods"
[7] "base"

other attached packages:
g.data
  "1.6"
 >

On 2/13/2007 1:34 PM, Tony Plate wrote:
> The help files for delayedAssign and substitute both say that 
> substitute() can be used to see the expression associated with a 
> promise.  However, I can't see how to do that.  When I try the example 
> in help file for delayedAssign I don't see substitute() extracting the 
> promise, e.g.:
> 
>  > msg <- "old"
>  > delayedAssign("x", msg)
>  > msg <- "new!"
>  > substitute(x) #- I would expect to see 'msg' here
> x
>  > x #- new!
> [1] "new!"
>  > substitute(x)
> x
>  >
> 
> Has this functionality been removed, and the docs not updated?  Or am I 
> missing something?
This is a misfeature that has been around forever.  The substitute() 
function works differently when the env argument is the global 
environment than it does in general.

 > delayedAssign("x", 1+2)
 > substitute(x)
x
 > e <- new.env()
 > delayedAssign("x", 1+2, assign.env = e)
 > substitute(x, e)
1 + 2

The documentation for substitute() indicates this, but perhaps not 
entirely unambiguously.

Duncan Murdoch
> 
> -- Tony Plate
> 
>  > sessionInfo()
> R version 2.4.1 (2006-12-18)
> i386-pc-mingw32
> 
> locale:
> LC_COLLATE=English_United States.1252;LC_CTYPE=English_United 
> States.1252;LC_MONETARY=English_United 
> States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252
> 
> attached base packages:
> [1] "stats"     "graphics"  "grDevices"
"utils"     "datasets"  "methods"
> [7] "base"
> 
> other attached packages:
> g.data
>   "1.6"
>  >
> 
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