[Rd] Expanding partial names

[Gabor Grothendieck]

Try this:


wrapper <- function(...) {
  args <- list(...)
  if (length(args)) {
	  nf <- names(formals(lowlevel))
	  nams <- nf[pmatch(names(args), nf)]
	  args <- replace(list(longname = 2), nams, args)
  }
  do.call("lowlevel", args)
}

Here is a test:

> wrapper()
longname =  1
> wrapper(longname = 34)
longname =  34
> wrapper(long = 34)
longname =  34


On 3/7/06, Duncan Murdoch <murdoch at stats.uwo.ca> wrote:
> I'm writing wrappers for some functions that change some of the default
> arguments.  I'd rather not list all of the arguments for the low level
> functions because there are about a dozen wrapper functions, and about
> 20 arguments to lowlevel.  Instead I'm trying something like this:
>
> lowlevel <- function(longname = 1) {
>   cat("longname = ", longname, "\n")
> }
>
> wrapper <- function(...) {
>   newargs <- list(longname = 2)
>   newargs[names(list(...))] <- list(...)
>   do.call("lowlevel", newargs)
> }
>
> This almost works:
>
>  > wrapper()
> longname =  2
>  > wrapper(longname = 3)
> longname =  3
>
> But it fails if I try to use partial argument matching:
>
>  > wrapper(long=4)
> Error in lowlevel(longname = 2, long = 4) :
>         unused argument(s) (long ...)
>
> because long isn't matched to longname.  Is there a reasonable way to do
> this (e.g. using pmatch or charmatch) other than listing all the low
> level arguments in the argument list to wrapper?
>
> Duncan Murdoch
>
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