[Rd] How to build a list with missing values? What is missing, anyway?

Peter Meilstrup peter.meilstrup at gmail.com
Fri Oct 5 00:53:12 CEST 2012

On Wed, Oct 3, 2012 at 11:21 PM, Josh O'Brien <joshmobrien at gmail.com> wrote:
>>Say I have argnames <- c("a", "b", "c").
> >From that I want to construct the equivalent of alist(a=, b=, c=).
> Here's a one liner that'll do that for you:
> argnames <- letters[1:3]
> setNames(rep(list(bquote()), length(argnames)), argnames)


Just so I have my mental model correct, I'm gathering that missing/``
is a symbol that the interpreter has a special rule for -- evaluating
it raises an error, as opposed to objects that evaluate to themselves
or variable names that evaluate to objects.

Does the same sort of thing explain the behavior of `...`? When the
interpreter comes across `...` in the arguments during evaluation of a
call, it trips a special argument-interpolating behavior?


More information about the R-devel mailing list