As of 3.5.0 the ...length() function does exactly what you are asking for.
Before that, I don't know of an easy way to get the length without
evaluation via R code. There may be one I'm not thinking of though, I
haven't needed to do this myself.
Hope that helps.
~G
On Thu, May 3, 2018 at 7:52 AM, Mark van der Loo <mark.vander...@gmail.com>
wrote:
> This question is better aimed at the r-help mailinglist as it is not about
> developing R itself.
>
>
> having said that,
>
> I can only gues why you want to do this, but why not do something like
> this:
>
>
> f <- function(...){
> L <- list(...)
> len <- length()
> # you can stll pass the ... as follows:
> do.call(someotherfunction, L)
>
> }
>
>
> -Mark
>
> Op do 3 mei 2018 om 16:29 schreef Dénes Tóth <toth.de...@kogentum.hu>:
>
> > Hi,
> >
> >
> > In some cases the number of arguments passed as ... must be determined
> > inside a function, without evaluating the arguments themselves. I use
> > the following construct:
> >
> > dotlength <- function(...) length(substitute(expression(...))) - 1L
> >
> > # Usage (returns 3):
> > dotlength(1, 4, something = undefined)
> >
> > How can I define a method for length() which could be called directly on
> > `...`? Or is it an intention to extend the base length() function to
> > accept ellipses?
> >
> >
> > Regards,
> > Denes
> >
> > ______________________________________________
> > R-devel@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>
--
Gabriel Becker, Ph.D
Scientist
Bioinformatics and Computational Biology
Genentech Research
[[alternative HTML version deleted]]
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
