R devel - Mar 2024 - capture "->"

Hi everyone,

I am aware this is a parser issue, but is there any possibility to capture
the use of the inverse assignment operator into a formula?

Something like:
> foo <- function(x) substitute(x)
gives:
> foo(A -> B)
B <- A

I wonder if there is any possibility whatsoever to signal the use of ->
instead of <-

Thank you,
Dmitri

	[[alternative HTML version deleted]]

On 01/03/2024 4:17 a.m., Dmitri Popavenko wrote:
> Hi everyone,
> 
> I am aware this is a parser issue, but is there any possibility to capture
> the use of the inverse assignment operator into a formula?
> 
> Something like:
> 
>> foo <- function(x) substitute(x)
> 
> gives:
> 
>> foo(A -> B)
> B <- A
> 
> I wonder if there is any possibility whatsoever to signal the use of ->
> instead of <-
If you parse it with srcrefs, you could look at the source.  The parser 
doesn't record whether it was A -> B or B <- A anywhere else.

Duncan Murdoch

Would it be good enough to pass it as a formula?  Using your definition of foo

  foo(~ A -> result)
  ## result <- ~A

  foo(~ result <- A)
  ## ~result <- A

On Fri, Mar 1, 2024 at 4:18?AM Dmitri Popavenko
<dmitri.popavenko at gmail.com> wrote:
>
> Hi everyone,
>
> I am aware this is a parser issue, but is there any possibility to capture
> the use of the inverse assignment operator into a formula?
>
> Something like:
>
> > foo <- function(x) substitute(x)
>
> gives:
>
> > foo(A -> B)
> B <- A
>
> I wonder if there is any possibility whatsoever to signal the use of ->
> instead of <-
>
> Thank you,
> Dmitri
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


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