how do I define a function which is equivalent to `deparse(substitute(x))`?

desub <- function(x) as.name(all.vars(sys.call(-1)))

g <- function(y)desub(y)
g(log)

Dear Frederick,

I found this a challenging puzzle, and it took me awhile to come up with an alternative, and I think slightly simpler, solution:

desub <- function(y) {

+     deparse(eval(substitute(substitute(y)),
+                  env=parent.frame()))
+ }

f <- function(x){

+     message(desub(x))
+ }

f(log)

log

Best,
 John

-----------------------------
John Fox, Professor
McMaster University
Hamilton, Ontario
Canada L8S 4M4
Web: socserv.mcmaster.ca/jfox

-----Original Message-----
From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
frederik at ofb.net
Sent: December 11, 2016 8:35 PM
To: r-help at r-project.org
Subject: Re: [R] how do I define a function which is equivalent to
`deparse(substitute(x))`?

Dear R-Help,

I was going to ask Jeff to read the entire works of William Shakespeare to learn
why his reply was not helpful to me...

Then I realized that the answer, as always, lies within...

    desub <- function(y) {
      e1=substitute(y, environment())
      e2=do.call(substitute,list(e1), env=parent.frame())
      deparse(e2)
    }

Sorry to trouble the list; other solutions still welcome.

Cheers,

Frederick

On Sun, Dec 11, 2016 at 12:46:23AM -0800, Jeff Newmiller wrote:

No. Read Hadley Wickham's "Advanced R" to learn why not.
--
Sent from my phone. Please excuse my brevity.

On December 10, 2016 10:24:49 PM PST, frederik at ofb.net wrote:

Dear R-Help,

I asked this question on StackOverflow,

http://stackoverflow.com/questions/41083293/in-r-how-do-i-define-a-fu
nction-which-is-equivalent-to-deparsesubstitutex

but thought perhaps R-help would be more appropriate.

I want to write a function in R which grabs the name of a variable
from the context of its caller's caller. I think the problem I have
is best understood by asking how to compose `deparse` and `substitute`.
You can see that a naive composition does not work:

   # a compose operator

   >  `%c%` = function(x,y)function(...)x(y(...))

   # a naive attempt to combine deparse and substitute

   > desub = deparse %c% substitute
   > f=function(foo) { message(desub(foo)) }
   > f(log)

   foo

   # this is how it is supposed to work

   > g=function(foo) { message(deparse(substitute(foo))) }
   > g(log)

   log

Is there a way I can define a function `desub` so that `desub(x)` has
the same value as `deparse(substitute(x))` in every context?

Thank you,

Frederick Eaton