[Rd] Pipe operator status, placeholders?

[Lionel Henry]

I think usage of the placeholder in nested calls is another question.
The placeholder requires a named argument to improve readability
because it's a single character that is easy to miss.

Best,
Lionel

On 4/19/22, peter dalgaard <pdalgd using gmail.com> 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
>>
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>
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