On Fri, Dec 4, 2020 at 7:35 PM Duncan Murdoch <murdoch.dun...@gmail.com> wrote: > > On 04/12/2020 8:13 a.m., Hiroaki Yutani wrote: > >> Error: function '::' not supported in RHS call of a pipe > > > > To me, this error looks much more friendly than magrittr's error. > > Some of them got too used to specify functions without (). This > > is OK until they use `::`, but when they need to use it, it takes > > hours to figure out why > > > > mtcars %>% base::head > > #> Error in .::base : unused argument (head) > > > > won't work but > > > > mtcars %>% head > > > > works. I think this is a too harsh lesson for ordinary R users to > > learn `::` is a function. I've been wanting for magrittr to drop the > > support for a function name without () to avoid this confusion, > > so I would very much welcome the new pipe operator's behavior. > > Thank you all the developers who implemented this! > > I agree, it's an improvement on the corresponding magrittr error. > > I think the semantics of not evaluating the RHS, but treating the pipe > as purely syntactical is a good decision. > > I'm not sure I like the recommended way to pipe into a particular argument: > > mtcars |> subset(cyl == 4) |> \(d) lm(mpg ~ disp, data = d) > > or > > mtcars |> subset(cyl == 4) |> function(d) lm(mpg ~ disp, data = d) > > both of which are equivalent to > > mtcars |> subset(cyl == 4) |> (function(d) lm(mpg ~ disp, data = d))() > > It's tempting to suggest it should allow something like > > mtcars |> subset(cyl == 4) |> lm(mpg ~ disp, data = .)
Which is really not that far off from mtcars |> subset(cyl == 4) |> \(.) lm(mpg ~ disp, data = .) once you get used to it. One consequence of the implementation is that it's not clear how multiple occurrences of the placeholder would be interpreted. With magrittr, sort(runif(10)) %>% ecdf(.)(.) ## [1] 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 This is probably what you would expect, if you expect it to work at all, and not ecdf(sort(runif(10)))(sort(runif(10))) There would be no such ambiguity with anonymous functions sort(runif(10)) |> \(.) ecdf(.)(.) -Deepayan > which would be expanded to something equivalent to the other versions: > but that makes it quite a bit more complicated. (Maybe _ or \. should > be used instead of ., since those are not legal variable names.) > > I don't think there should be an attempt to copy magrittr's special > casing of how . is used in determining whether to also include the > previous value as first argument. > > Duncan Murdoch > > > > > > Best, > > Hiroaki Yutani > > > > 2020年12月4日(金) 20:51 Duncan Murdoch <murdoch.dun...@gmail.com>: > >> > >> Just saw this on the R-devel news: > >> > >> > >> R now provides a simple native pipe syntax ‘|>’ as well as a shorthand > >> notation for creating functions, e.g. ‘\(x) x + 1’ is parsed as > >> ‘function(x) x + 1’. The pipe implementation as a syntax transformation > >> was motivated by suggestions from Jim Hester and Lionel Henry. These > >> features are experimental and may change prior to release. > >> > >> > >> This is a good addition; by using "|>" instead of "%>%" there should be > >> a chance to get operator precedence right. That said, the ?Syntax help > >> topic hasn't been updated, so I'm not sure where it fits in. > >> > >> There are some choices that take a little getting used to: > >> > >> > mtcars |> head > >> Error: The pipe operator requires a function call or an anonymous > >> function expression as RHS > >> > >> (I need to say mtcars |> head() instead.) This sometimes leads to error > >> messages that are somewhat confusing: > >> > >> > mtcars |> magrittr::debug_pipe |> head > >> Error: function '::' not supported in RHS call of a pipe > >> > >> but > >> > >> mtcars |> magrittr::debug_pipe() |> head() > >> > >> works. > >> > >> Overall, I think this is a great addition, though it's going to be > >> disruptive for a while. > >> > >> Duncan Murdoch > >> > >> ______________________________________________ > >> R-devel@r-project.org mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-devel > > > > ______________________________________________ > > R-devel@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel