Unpacking argument lists for ellipsis in R

Question

I am confused by the use of the ellipsis (...) in some functions, i.e. how to pass an object containing the arguments as a single argument.

In Python it

Answer 1

It took me a while to find it, but the purrr package has an equivalent to plyr::splat: it's called lift_dl.

The "dl" in the name stands for "dots to list", as it's part of a series of lift_xy functions that can be used to "lift" the domain of a function from one kind of input to another kind, these "kinds" being lists, vectors and "dots".

Since lift_dl is probably the most useful of those, there is a simple lift alias provided for it.

To reuse the above example:

> library(purrr)
> args <- c('baz', 'foob')
> lift(file.path)(c('/foo/bar', args))
[1] "/foo/bar/baz/foob"