[Rd] [External] brief update on the pipe operator in R-devel
Bill Dunlap
w||||@mwdun|@p @end|ng |rom gm@||@com
Tue Jan 12 21:52:10 CET 2021
'=>' can be defined as a function. E.g., it could be the logical "implies"
function:
> `=>` <- function(x, y) !x | y
> TRUE => FALSE
[1] FALSE
> FALSE => TRUE
[1] TRUE
It might be nice then to have deparse() display it as an infix operator
instead of the current prefix:
> deparse(quote(p => q))
[1] "`=>`(p, q)"
There was a user who recently wrote asking for an infix operator like -> or
=> that would deparse nicely for use in some sort of model specification.
When used with |>, the parser will turn the |> and => into an ordinary
looking function call so deparsing is irrelevant.
> deparse(quote(x |> tmp => f(7,arg2=tmp)))
[1] "f(7, arg2 = x)"
-Bill
On Tue, Jan 12, 2021 at 12:01 PM Dirk Eddelbuettel <edd using debian.org> wrote:
>
> On 12 January 2021 at 20:38, Iñaki Ucar wrote:
> | On Tue, 12 Jan 2021 at 20:23, <luke-tierney using uiowa.edu> wrote:
> | >
> | > After some discussions we've settled on a syntax of the form
> | >
> | > mtcars |> subset(cyl == 4) |> d => lm(mpg ~ disp, data = d)
> | >
> | > to handle cases where the pipe lhs needs to be passed to an argument
> | > other than the first of the function called on the rhs. This seems a
> | > to be a reasonable balance between making these non-standard cases
> | > easy to see but still easy to write. This is now committed to R-devel.
> |
> | Interesting. Is the use of "d =>" restricted to pipelines? In other
> | words, I think that it shouldn't be equivalent to "function(d)", i.e.,
> | that this:
> |
> | x <- d => lm(mpg ~ disp, data = d)
> |
> | shouldn't work.
>
> Looks like your wish was already granted:
>
> > mtcars |> subset(cyl == 4) |> d => lm(mpg ~ disp, data = d)
>
> Call:
> lm(formula = mpg ~ disp, data = subset(mtcars, cyl == 4))
>
> Coefficients:
> (Intercept) disp
> 40.872 -0.135
>
> > d => lm(mpg ~ disp, data = d)
> Error in `=>`(d, lm(mpg ~ disp, data = d)) : could not find function "=>"
> > x <- d => lm(mpg ~ disp, data = d)
> Error in `=>`(d, lm(mpg ~ disp, data = d)) : could not find function "=>"
> >
>
> Dirk
>
> --
> https://dirk.eddelbuettel.com | @eddelbuettel | edd using debian.org
>
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