[Rd] R-devel's ...names() questions

William Dunlap wdun|@p @end|ng |rom t|bco@com
Fri May 22 20:53:12 CEST 2020

Am am missing something or does the new ...names() in R-devel not work

> a <- function(x, ...) ...names()
> a(a=stop("a"), b=stop("b"))
[1] "a" ""
> a(stop("x"), stop("unnamed"), c=stop("c"), d=stop("d"))
[1] NA "" ""

> version
platform       x86_64-pc-linux-gnu
arch           x86_64
os             linux-gnu
system         x86_64, linux-gnu
status         Under development (unstable)
major          4
minor          1.0
year           2020
month          05
day            19
svn rev        78492
language       R
version.string R Under development (unstable) (2020-05-19 r78492)
nickname       Unsuffered Consequences

The following seems to do the right thing
alt...names <- function() evalq(names(substitute(...())),

However I wonder if it would be better to give the user a function, say
...args_unevaluated(...) to get the unevaluated ... arguments directlly
without having to know about the substitute(...()) trick.   Then the user
could get the length, the n'th, or the names using the usual length(), [[,
and names() functions instead of ...length(), ...elt(), and ...names().

Bill Dunlap
TIBCO Software
wdunlap tibco.com

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