[R] how do I define a function which is equivalent to `deparse(substitute(x))`?
Fox, John
jfox at mcmaster.ca
Tue Dec 13 00:58:00 CET 2016
Dear Bert,
It's nitpicking, I guess, but the call to message() is in the original posting. Your solution produces
> desub <- function(x) as.name(all.vars(sys.call(-1)))
> f <- function(x){
+ message(desub(x))
+ }
> f(log)
x
Best,
John
> -----Original Message-----
> From: Bert Gunter [mailto:bgunter.4567 at gmail.com]
> Sent: Monday, December 12, 2016 6:41 PM
> To: Fox, John <jfox at mcmaster.ca>
> Cc: frederik at ofb.net; r-help at r-project.org
> Subject: Re: [R] how do I define a function which is equivalent to
> `deparse(substitute(x))`?
>
> *If* I understand correctly -- and please let me know if I don't -- this
> seems somewhat more straightforward and less "hacky" :
>
> > desub <- function(x) as.name(all.vars(sys.call(-1)))
>
> Yielding in the OP's example:
>
> > g <- function(y)desub(y)
> > g(log)
> log
>
> Cheers,
> Bert
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along
> and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Mon, Dec 12, 2016 at 2:07 PM, Fox, John <jfox at mcmaster.ca> wrote:
> > 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
> >> > >
> >> > >______________________________________________
> >> > >R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> > >https://stat.ethz.ch/mailman/listinfo/r-help
> >> > >PLEASE do read the posting guide
> >> > >http://www.R-project.org/posting-guide.html
> >> > >and provide commented, minimal, self-contained, reproducible code.
> >> >
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> https://stat.ethz.ch/mailman/listinfo/r-help
> >> PLEASE do read the posting guide
> >> http://www.R-project.org/posting-guide.html
> >> and provide commented, minimal, self-contained, reproducible code.
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
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