[Rd] [External] Re: New pipe operator
iuke-tier@ey m@iii@g oii uiow@@edu
iuke-tier@ey m@iii@g oii uiow@@edu
Sun Dec 6 20:15:40 CET 2020
On Sun, 6 Dec 2020, Gabor Grothendieck wrote:
> Why is that ambiguous? It works in magrittr.
For now, all functions marked internally as syntactically special are
disallowed. Not all of these lead to ambiguities.
Best,
luke
>
>> library(magrittr)
>> 1 %>% `+`()
> [1] 1
>
> On Sun, Dec 6, 2020 at 1:09 PM <luke-tierney using uiowa.edu> wrote:
>>
>> On Sun, 6 Dec 2020, Gabor Grothendieck wrote:
>>
>>> The following gives an error.
>>>
>>> 1 |> `+`(2)
>>> ## Error: function '+' is not supported in RHS call of a pipe
>>>
>>> 1 |> `+`()
>>> ## Error: function '+' is not supported in RHS call of a pipe
>>>
>>> but this does work:
>>>
>>> 1 |> (`+`)(2)
>>> ## [1] 3
>>>
>>> 1 |> (`+`)()
>>> ## [1] 1
>>>
>>> The error message suggests that this was intentional.
>>> It isn't mentioned in ?"|>"
>>
>> ?"|>" says:
>>
>> To avoid ambiguities, functions in ‘rhs’ calls may not
>> be syntactically special, such as ‘+’ or ‘if’.
>>
>> (used to say lhs; fixed now).
>>
>> Best,
>>
>> luke
>>
>>>
>>> On Sat, Dec 5, 2020 at 1:19 PM <luke-tierney using uiowa.edu> wrote:
>>>>
>>>> We went back and forth on this several times. The key advantage of
>>>> requiring parentheses is to keep things simple and consistent. Let's
>>>> get some experience with that. If experience shows requiring
>>>> parentheses creates too many issues then we can add the option of
>>>> dropping them later (with special handling of :: and :::). It's easier
>>>> to add flexibility and complexity than to restrict it after the fact.
>>>>
>>>> Best,
>>>>
>>>> luke
>>>>
>>>> On Sat, 5 Dec 2020, Hugh Parsonage 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.sarkar using gmail.com> wrote:
>>>>>>
>>>>>> On Fri, Dec 4, 2020 at 7:35 PM Duncan Murdoch <murdoch.duncan using 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.duncan using 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 using r-project.org mailing list
>>>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>>>>>>
>>>>>>>> ______________________________________________
>>>>>>>> R-devel using r-project.org mailing list
>>>>>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>>>>>>
>>>>>>>
>>>>>>> ______________________________________________
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>>>>>>
>>>>>> ______________________________________________
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>>>>>
>>>>> ______________________________________________
>>>>> R-devel using r-project.org mailing list
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>>>>>
>>>>
>>>> --
>>>> Luke Tierney
>>>> Ralph E. Wareham Professor of Mathematical Sciences
>>>> University of Iowa Phone: 319-335-3386
>>>> Department of Statistics and Fax: 319-335-3017
>>>> Actuarial Science
>>>> 241 Schaeffer Hall email: luke-tierney using uiowa.edu
>>>> Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
>>>> ______________________________________________
>>>> R-devel using r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>
>>>
>>>
>>>
>>
>> --
>> Luke Tierney
>> Ralph E. Wareham Professor of Mathematical Sciences
>> University of Iowa Phone: 319-335-3386
>> Department of Statistics and Fax: 319-335-3017
>> Actuarial Science
>> 241 Schaeffer Hall email: luke-tierney using uiowa.edu
>> Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
>
>
>
>
--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tierney using uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
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