From h.wickham at gmail.com  Wed Mar 22 16:38:33 2017
From: h.wickham at gmail.com (Hadley Wickham)
Date: Thu, 23 Mar 2017 04:38:33 +1300
Subject: [Rd] RFC: (in-principle) native unquoting for standard
	evaluation
In-Reply-To: <CABdHhvHttoH7yNTG7bj=nKdfRd1c2yukDWaovqid+PfT6+yHMA@mail.gmail.com>
References: <mailman.9.1489921202.31343.r-devel@r-project.org>
	<20170319183610.GA26048@mail.cs.toronto.edu>
	<CABdHhvHttoH7yNTG7bj=nKdfRd1c2yukDWaovqid+PfT6+yHMA@mail.gmail.com>
Message-ID: <CABdHhvFcwMZBw1v8q47rCCU=kLZ9mCFQXoXC45K91LLOcrRXHQ@mail.gmail.com>

On Mon, Mar 20, 2017 at 8:00 AM, Hadley Wickham <h.wickham at gmail.com> wrote:
> On Mon, Mar 20, 2017 at 7:36 AM, Radford Neal <radford at cs.toronto.edu> wrote:
>> Michael Lawrence (as last in long series of posters)...
>>
>>> Yes, it would bind the language object to the environment, like an
>>> R-level promise (but "promise" of course refers specifically to just
>>> _lazy_ evaluation).
>>>
>>> For the uqs() thing, expanding calls like that is somewhat orthogonal
>>> to NSE. It would be nice in general to be able to write something like
>>> mean(x, extra_args...) without resorting to do.call(mean, c(list(x),
>>> extra_args)). If we had that then uqs() would just be the combination
>>> of unquote and expansion, i.e., mean(x, @extra_args...). The "..."
>>> postfix would not work since it's still a valid symbol name, but we
>>> could come up with something.
>>
>>
>> I've been trying to follow this proposal, though without tracking down
>> all the tweets, etc. that are referenced.  I suspect I'm not the only
>> reader who isn't clear exactly what is being proposed.  I think a
>> detailed, self-contained proposal would be useful.
>
> We have a working implementation (which I'm calling tidyeval) in
> https://github.com/hadley/rlang, but we have yet to write it up. We'll
> spend some time documenting since it seems to be of broader interest.

First pass at programming dplyr vignette (including details about tidyeval) at
http://rpubs.com/hadley/dplyr-programming

Hadley

-- 
http://hadley.nz



[Rd] RFC: (in-principle) native unquoting for standard evaluation
Hadley Wickham