Whoops, just noticed that I cut when I should have copied. The newArgs
function should look like this:
newArgs <- function(..., Params) {
f <- function(...) list(...)
formals(f) <- c(Params, formals(f))
names <- as.list(names(Params))
names(names) <- names
names <- lapply(names, as.name)
b <- as.list(body(f))
body(f) <- as.call(c(b[1], names, b[-1]))
f(...)
}
Duncan Murdoch
On 3/7/2006 9:18 PM, Duncan Murdoch wrote:
> Okay, here's my effort based on Deepayan's and Charles' ideas. The
> newArgs function is not what I'd call transparent, but I like the way
> the wrapper looks.
>
> > newArgs <- function(..., Params) {
> + f <- function(...) list(...)
> + formals(f) <- c(Params, formals(f))
>
> + b <- as.list(body(f))
> + body(f) <- as.call(c(b[1], names, b[-1]))
> + f(...)
> + }
> >
> > lowlevel <- function(longname = 1) {
> + cat("longname = ", longname, "\n")
> + }
> >
> > newDefaults <- list(longname=2)
> >
> > wrapper <- function (...)
> + do.call("lowlevel", newArgs(..., Params=newDefaults))
>
> newArgs sets up f to look like
>
> function (longname = 2, ...) list(longname = longname, ...)
>
> and then calls it. The thing I like about this, as opposed to using
> pmatch, is that I'm sure the partial matching is what's used by R's
> argument matching, whereas that's only pretty likely with pmatch.
>
> I also sort of like these lines:
>
> + names <- as.list(names(Params))
> + names(names) <- names
> + names <- lapply(names, as.name)
>
> but maybe I should have named Params as names, so they looked like this:
>
> + names <- as.list(names(names))
> + names(names) <- names
> + names <- lapply(names, as.name)
>
> And of course I like the fact that this seems to work, but we've seen
> several versions that do that:
>
> > wrapper()
> longname = 2
> > wrapper(longname=3)
> longname = 3
> > wrapper(long=3)
> longname = 3
> > wrapper(long=20)
> longname = 20
> > wrapper(junk=20)
> Error in lowlevel(longname = 2, junk = 20) :
> unused argument(s) (junk ...)
>
> Duncan Murdoch
>
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