[Rd] Convenience function to get unevaluated ... function arguments

[Warnes, Gregory]

I'll be glad to add it to the gtools package if it doesn't (immediately) go into one of the core packages.

Sent from my iPhone

On Jul 26, 2012, at 7:35 AM, "Bert Gunter" <gunter.berton at gene.com> wrote:

> Indeed!
> 
> -- Bert
> 
> On Wed, Jul 25, 2012 at 3:59 PM, David Winsemius <dwinsemius at comcast.net> wrote:
>> 
>> On Jul 24, 2012, at 4:39 PM, Bert Gunter wrote:
>> 
>>> Folks:
>>> 
>>> Herein is a suggestion for a little R convenience function mainly to
>>> obtain unevaluated ... function arguments. It arose from a query on
>>> R-help on how to get these arguments. The standard (I think) idiom to
>>> do this is via
>>> 
>>> match.call(expand.dots=FALSE)$...
>>> 
>>> However, Bill Dunlap pointed out that this repeats the argument
>>> matching of the function call and suggested a couple of alternatives
>>> that do not, one of which I've adapted as the following function,fun
>>> (I'll comment on naming in a second):
>>> 
>>> fun <- as.list(substitute((...), env = parent.frame()))[-1]
>> 
>> 
>> I think instead:
>> 
>> fun <- function() as.list(substitute((...), env = parent.frame()))[-1]
>> 
>> --
>> David.
>>> 
>>> 
>>> Typical usage would be:
>>> 
>>> f <- function(x, ...,y)fun()
>>> 
>>> e.g.
>>> 
>>>> f(x = 5,z=sin(a),y=3,stop("oh"),w=warning("Yikes"))
>>> 
>>> $z
>>> sin(a)
>>> 
>>> [[2]]
>>> stop("oh")
>>> 
>>> $w
>>> warning("Yikes")
>>> 
>>> It turns out that (surprisingly to me) the substitute idiom is faster
>>> than the match.call idiom, although the difference appears
>>> unimportant, since both are so fast. And it is a little slower when
>>> wrapped into a function, anyway -- I wasn't able to figure out a
>>> convenient way to wrap the match.call version into a function.
>>> 
>>> The question is where -- if anywhere -- should this little one-liner
>>> go? Seems to me that there are 3 possibilities:
>>> 1. Nowhere. Unnecessary and trivial.  An entirely reasonable response,
>>> imho; I leave it to guRus to make this judgment.
>>> 
>>> 2. In with match.call(); in which case a name like match.dots would
>>> seem appropriate.
>>> 
>>> 3. In with substitute(); in which case something like substituteDots
>>> to make the relationship clear might be appropriate.
>>> 
>>> If R core or others do want to use this, I would be happy to write the
>>> line or two of additional documentation required (if no one else wants
>>> to).
>>> 
>>> And to repeat... I know this is trivial, so no explanation or response
>>> is needed if it is decided to ignore it.
>>> 
>>> Best,
>>> Bert
>>> 
>>> 
>>> 
>>> 
>>> --
>>> 
>>> Bert Gunter
>>> Genentech Nonclinical Biostatistics
>>> 
>>> Internal Contact Info:
>>> Phone: 467-7374
>>> Website:
>>> 
>>> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
>>> 
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>> 
>> 
>> David Winsemius, MD
>> Heritage Laboratories
>> West Hartford, CT
>> 
> 
> 
> 
> -- 
> 
> Bert Gunter
> Genentech Nonclinical Biostatistics
> 
> Internal Contact Info:
> Phone: 467-7374
> Website:
> http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel