From h.wickham at gmail.com  Mon Feb 18 19:33:14 2013
From: h.wickham at gmail.com (Hadley Wickham)
Date: Mon, 18 Feb 2013 12:33:14 -0600
Subject: [Rd] quote() vs quote(expr=)
In-Reply-To: <alpine.LFD.2.03.1302181227030.10691@uiowa.edu>
References: <CABdHhvGwS1xuOqYLqtJAGjJrm5gGvLW7XJs+4bg3LY_R3Z7oNQ@mail.gmail.com>
	<alpine.LFD.2.03.1302181227030.10691@uiowa.edu>
Message-ID: <CABdHhvFs3voJjhQ7oCMMxXSTkDvAQje_Nr2dnkWJsMwJf9z0qA@mail.gmail.com>

In general, should we expect that the ability to compute on the
language within R will decrease over time? Otherwise, I presume if you
do change the behaviour of missing then you'll still provide some way
to create/call functions with missing arguments.

Hadley

On Mon, Feb 18, 2013 at 12:31 PM,  <luke-tierney at uiowa.edu> wrote:
> I wouldn't count on any way of capturing this thing being reliable in
> the long term.  As I recall what I do in codetools and the compiler is
> use features of missing() to test for it, but try to abstract those
> uses into one or two places only so I can easily change them if
> missing()'s behavior changes. Basically this internal thing
> _shouldn't_ be visible at R level, and if we ever figure out how to
> make that happen it will.
>
> Best,
>
> luke
>
>
> On Mon, 18 Feb 2013, Hadley Wickham wrote:
>
>> Hi all,
>>
>> I think there's a small buglet in quote:
>>
>> str(quote())
>> # Error in quote() : 0 arguments passed to 'quote' which requires 1
>> str(quote(expr = ))
>> # symbol
>>
>> I bring this up because this seems like the most natural way of
>> capturing the "missing" symbol with pure R code, compared to
>> substitute() or bquote() or formals(plot)$x
>>
>> Hadley
>>
>>
>
> --
> Luke Tierney
> Chair, Statistics and Actuarial Science
> 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 at uiowa.edu
> Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu



-- 
Chief Scientist, RStudio
http://had.co.nz/



[Rd] quote() vs quote(expr=)
Hadley Wickham