What is "..." when it's empty? -- differences to S

[Martin Maechler]

i)       (function(x, ...) length(...))(1)

gives 0 in S (plus 3.4) and an error in R.
It also gives an error in Splus 5.0r3.
So we could well remain as we are... however

ii)	(function(x, ...) length(...))(1,2)

gives 1  in all dialects of S that I have available.
So by my `continuation logic', I'd argue that  "i)" above should give 0
(and R and S-plus 5.0r3 behave inconsistently.

Do we yet have any documentation on "..." ??

In both Splus 3.4 and 5.0r3,
   (function(x, ...) mode(...))(1)	returns "missing"
whereas R gives an interesting error:
    R> trace(mode)
    R> (function(x, ...) mode(...))(1)
    trace: mode(...)
    Error: Argument "x" is missing, with no default

---
What is desired for R?

BTW: Found the above problem when trying to use 
       C(<factor>) without a 2nd argument;  a patch for that will be in the 
       snapshots..

Martin Maechler <maechler@stat.math.ethz.ch>	http://stat.ethz.ch/~maechler/
Seminar fuer Statistik, ETH-Zentrum SOL G1;	Sonneggstr.33
ETH (Federal Inst. Technology)	8092 Zurich	SWITZERLAND
phone: x-41-1-632-3408		fax: ...-1086			<><
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