From luke-tierney at uiowa.edu  Mon Feb 18 19:43:01 2013
From: luke-tierney at uiowa.edu (luke-tierney at uiowa.edu)
Date: Mon, 18 Feb 2013 12:43:01 -0600
Subject: [Rd] quote() vs quote(expr=)
In-Reply-To: <CABdHhvFs3voJjhQ7oCMMxXSTkDvAQje_Nr2dnkWJsMwJf9z0qA@mail.gmail.com>
References: <CABdHhvGwS1xuOqYLqtJAGjJrm5gGvLW7XJs+4bg3LY_R3Z7oNQ@mail.gmail.com>
	<alpine.LFD.2.03.1302181227030.10691@uiowa.edu>
	<CABdHhvFs3voJjhQ7oCMMxXSTkDvAQje_Nr2dnkWJsMwJf9z0qA@mail.gmail.com>
Message-ID: <alpine.LFD.2.03.1302181238210.10691@uiowa.edu>

Of course not. What I hope can happpen is that we can reduce the
degree to which internal implementation quirks leak out into the user
level. The fact that there is an internal "missing token" (that
happens to be used for a couple of different things) is a quirk; if
you look at the code I use you can see why it is a quirk. Cleaning
this up will help computing on the language (at least that is the
hope).

luke

On Mon, 18 Feb 2013, Hadley Wickham wrote:

> 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
>
>
>
>

-- 
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



[Rd] quote() vs quote(expr=)
luke-tierney at uiowa.edu