On 3/7/2006 12:08 PM, Charles Dupont wrote:
> Duncan Murdoch 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
>
> If all you are doing is changing the default values of some arguments
> this should work.
>
> wrapper <- lowlevel
> formals(wrapper) <- replace(formals(lowlevel), c("longname"), list(2))
Thanks for the suggestion, but the calculation of the new defaults is
more involved than my example indicated. I really need to do some
computation within the wrapper to come up with the new defaults.
Duncan Murdoch
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