[Rd] [External] Re: Pipe operator status, placeholders?

[iuke-tier@ey m@iii@g oii uiow@@edu]

At some point there will probably be a blog post about the design of
the forward pipe operator in base, but that is not something I will
think about until after the current semester is over and my backlog of
other things is cleared.

Best,

luke

On Tue, 19 Apr 2022, peter dalgaard wrote:

> You probably want Luke Tierney for the full story, but what I gather from the deliberations (on the private R-core list), there are issues with how non-funcall syntax like lm(....) |> _$coef[2] should work. This, in turn, has to do with wanting to have the placeholder occur only as a toplevel substitution (i.e. "["("$"(_, coef), 2) is a no-go. And the reason for that has to do with the way the pipe works in the absense of placeholder, e.g. the parser gets confused by
>
>> x |> f(g(x=_))
> Error in f(x, g(x = "_")) : invalid use of pipe placeholder
>
> -pd
>
>> On 17 Apr 2022, at 01:04 , Benjamin Redelings <benjamin.redelings using gmail.com> wrote:
>>
>> Hi,
>>
>> I see that R 4.2 adds the underscore _ as a placeholder for the new forward pipe operator |> , but only for named arguments. The reason why placeholders for position arguments was NOT added isn't clear to me, so I've been looking for the discussion around the introduction of the placeholder.
>>
>> By searching subject lines in the r-devel mailing list archive, I've found
>>
>>     https://stat.ethz.ch/pipermail/r-devel/2021-April/080646.html
>>
>> https://stat.ethz.ch/pipermail/r-devel/2021-January/080396.html
>>
>> https://stat.ethz.ch/pipermail/r-devel/2020-December/080173.html and following messages
>>
>> but not much else.
>>
>> 1. Am I looking in the wrong place?
>>
>> 2. What is the reasoning behind allowing _ as a placeholder only for named arguments?
>>
>> take care,
>>
>> -BenRI
>>
>> ______________________________________________
>> 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
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