Thanks, this makes sense. Is there a similar precedence reasoning behind why operator functions (`+` etc) can't be piped into?
On Fri, Apr 21, 2023 at 11:52 PM Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > On 21/04/2023 4:35 a.m., Michael Milton wrote: > > I just checked out R-devel and noticed that the new "pipe extractor" > > capability coming in 4.3 only works for the 4 extractor operators, but no > > other standard operators like +, *, %*% etc, meaning that e.g. mtcars |> > > as.matrix() |> _ + 1 |> colMeans() is a syntax error. In addition, we are > > still subject to the restriction that the functions on the RHS of a pipe > > can't have special names, so mtcars |> as.matrix() |> `+`(1) |> > colMeans() is > > also a syntax error. > > > > Either option would be great, as I find it much cleaner to coordinate a > > sequence of function calls using pipes rather than nested function calls > or > > using temporary variables. > > > > May I enquire why both of these expressions are disallowed, and if it > might > > be possible to help remove one or both of these restrictions? There is > some > > discussion at > > https://stat.ethz.ch/pipermail/r-devel/2020-December/080210.html but the > > thread is mostly concerned with other things like the placeholder and > > whether or not parentheses can be omitted. My naive view is that piping > > into a special operator function like `+` would be the least ambiguous: > `+` > > presumably parses to the same type of token as `colMeans` does, so the > > function parse tree seems like it would work fine if this was allowed in > a > > pipe. > > If it were allowed, people would expect expressions like yours to work, > but as ?Syntax says, your pipe would actually be parsed as something like > > (mtcars |> as.matrix() |> _) + (1 |> colMeans()) > > because the |> operator has higher precedence than +. > > Since parens would be needed somewhere to override this, you may as well > type > > (as.matrix(mtcars) + 1) |> colMeans() > > which is both shorter and arguably clearer than > > mtcars |> as.matrix() |> (_ + 1) |> colMeans() > > Duncan Murdoch > > > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
