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

[Benjamin Redelings]

Completely understandable.  I'll look forward to hearing more about it 
later.

-BenRI

On 4/21/22 11:57 AM, luke-tierney using uiowa.edu wrote:
> 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
>>
>>
>