On 3/7/06, Duncan Murdoch <[EMAIL PROTECTED]> 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?
One trick I often use that is different from any of the suggestions I have seen
so far (and is more transparent IMO) is the following:
lowlevel <- function(longname = 1) {
cat("longname = ", longname, "\n")
}
wrapper <- function(...) {
newArgs <-
function(longname = 2, ...)
list(longname = longname,
...)
do.call("lowlevel", newArgs(...))
}
which gives:
> wrapper()
longname = 2
> wrapper(longname = 3)
longname = 3
> wrapper(long=20)
longname = 20
> wrapper(junk=3)
Error in lowlevel(longname = 2, junk = 3) :
unused argument(s) (junk ...)
-Deepayan
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