From luke-tierney at uiowa.edu  Mon Feb 18 19:31:10 2013
From: luke-tierney at uiowa.edu (luke-tierney at uiowa.edu)
Date: Mon, 18 Feb 2013 12:31:10 -0600
Subject: [Rd] quote() vs quote(expr=)
In-Reply-To: <CABdHhvGwS1xuOqYLqtJAGjJrm5gGvLW7XJs+4bg3LY_R3Z7oNQ@mail.gmail.com>
References: <CABdHhvGwS1xuOqYLqtJAGjJrm5gGvLW7XJs+4bg3LY_R3Z7oNQ@mail.gmail.com>
Message-ID: <alpine.LFD.2.03.1302181227030.10691@uiowa.edu>

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



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