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

From: Peter Meilstrup <>
Date: Thu, 04 Oct 2012 15:53:12 -0700

On Wed, Oct 3, 2012 at 11:21 PM, Josh O'Brien <> 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?

Peter mailing list Received on Thu 04 Oct 2012 - 22:55:52 GMT

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