I understand very well that it is implemented at the syntax level; however, in any case the implementation is irrelevant to the principles.
Here a similar example to the one I gave before but this time written out: This works: 3 |> function(x) x + 1 but this does not: foo <- function(x) x + 1 3 |> foo so it breaks the principle of functions being first class objects. foo and its definition are not interchangeable. You have to write 3 |> foo() but don't have to write 3 |> (function(x) x + 1)(). This isn't just a matter of notation, i.e. foo vs foo(), but is a matter of breaking the way R works as a functional language with first class functions. On Sun, Dec 6, 2020 at 4:06 PM Gabriel Becker <gabembec...@gmail.com> wrote: > > Hi Gabor, > > On Sun, Dec 6, 2020 at 12:52 PM Gabor Grothendieck <ggrothendi...@gmail.com> > wrote: >> >> I think the real issue here is that functions are supposed to be >> first class objects in R >> or are supposed to be and |> would break that if if is possible >> to write function(x) x + 1 on the RHS but not foo (assuming foo >> was defined as that function). >> >> I don't think getting experience with using it can change that >> inconsistency which seems serious to me and needs to >> be addressed even if it complicates the implementation >> since it drives to the heart of what R is. >> > > With respect I think this is a misunderstanding of what is happening here. > > Functions are first class citizens. |> is, for all intents and purposes, a > macro. > > LHS |> RHS(arg2=5) > > parses to > > RHS(LHS, arg2 = 5) > > There are no functions at the point in time when the pipe transformation > happens, because no code has been evaluated. To know if a symbol is going to > evaluate to a function requires evaluation which is a step entirely after the > one where the |> pipe is implemented. > > Another way to think about it is that > > LHS |> RHS(arg2 = 5) > > is another way of writing RHS(LHS, arg2 = 5), NOT R code that is (or even can > be) evaluated. > > > Now this is a subtle point that only really has implications in as much as it > is not the case for magrittr pipes, but its relevant for discussions like > this, I think. > > ~G > >> On Sat, Dec 5, 2020 at 1:08 PM Gabor Grothendieck >> <ggrothendi...@gmail.com> wrote: >> > >> > The construct utils::head is not that common but bare functions are >> > very common and to make it harder to use the common case so that >> > the uncommon case is slightly easier is not desirable. >> > >> > Also it is trivial to write this which does work: >> > >> > mtcars %>% (utils::head) >> > >> > On Sat, Dec 5, 2020 at 11:59 AM Hugh Parsonage <hugh.parson...@gmail.com> >> > wrote: >> > > >> > > I'm surprised by the aversion to >> > > >> > > mtcars |> nrow >> > > >> > > over >> > > >> > > mtcars |> nrow() >> > > >> > > and I think the decision to disallow the former should be >> > > reconsidered. The pipe operator is only going to be used when the rhs >> > > is a function, so there is no ambiguity with omitting the parentheses. >> > > If it's disallowed, it becomes inconsistent with other treatments like >> > > sapply(mtcars, typeof) where sapply(mtcars, typeof()) would just be >> > > noise. I'm not sure why this decision was taken >> > > >> > > If the only issue is with the double (and triple) colon operator, then >> > > ideally `mtcars |> base::head` should resolve to `base::head(mtcars)` >> > > -- in other words, demote the precedence of |> >> > > >> > > Obviously (looking at the R-Syntax branch) this decision was >> > > considered, put into place, then dropped, but I can't see why >> > > precisely. >> > > >> > > Best, >> > > >> > > >> > > Hugh. >> > > >> > > >> > > >> > > >> > > >> > > >> > > >> > > On Sat, 5 Dec 2020 at 04:07, Deepayan Sarkar <deepayan.sar...@gmail.com> >> > > wrote: >> > > > >> > > > 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 >> > > >> > > ______________________________________________ >> > > R-devel@r-project.org mailing list >> > > https://stat.ethz.ch/mailman/listinfo/r-devel >> > >> > >> > >> > -- >> > Statistics & Software Consulting >> > GKX Group, GKX Associates Inc. >> > tel: 1-877-GKX-GROUP >> > email: ggrothendieck at gmail.com >> >> >> >> -- >> Statistics & Software Consulting >> GKX Group, GKX Associates Inc. >> tel: 1-877-GKX-GROUP >> email: ggrothendieck at gmail.com >> >> ______________________________________________ >> R-devel@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-devel -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
