[Rd] Test for argument in ...

[Gregor Gorjanc]

Hi,

Gabor Grothendieck wrote:
> Try this:
> 
>> f <- function(...) if (!is.null(list(...)$arg1)) cat("arg1 found\n")
>> else cat("arg1 not found\n")
>> f(arg1 = 3)
> arg1 found
>> f(arg2 = 3)
> arg1 not found

Actually it is not OK. Bellow is simplified example that shows, what I
would like to do:

foo1 <- function(x, ...)
{
  if(is.null(list(...)$decreasing)) {
    decreasing <- TRUE
  } else {
    decreasing <- list(...)$decreasing
  }
  return(order(x, ..., decreasing=decreasing))
}

> foo1(c(5, 2, 3, 4))
[1] 1 4 3 2

>foo1(c(5, 2, 3, 4), decreasing=FALSE)
Error in order(x, ..., decreasing = decreasing) :
        formal argument "decreasing" matched by multiple actual arguments

> On 7/1/06, Gregor Gorjanc <gregor.gorjanc at gmail.com> wrote:
>> Hello!
>>
>> Say I have a function foo1, which has argument ... to pass various
>> arguments to foo2 i.e.
>>
>> foo1 <- function(x, ...)
>> {
>>  foo2(x, ...)
>> }
>>
>> Say that foo2 accepts argument arg1 and I would like to do the following:
>> - if foo1 is called as foo1(x) then I would like to assign some value to
>> arg1 inside foo1 before calling foo2
>>
>> arg1 <- "some value"
>> foo2(x, arg1=arg1)
>>
>> - if foo1 is called foo1(arg1="some other value") do not assign some
>> value to arg1 and call foo2
>>
>> foo2(arg1=arg1)
>>
>> However, I am not able to do this since I do not know how to test/check
>> if arg1 was given in foo1. Is it possible to test whether some argument
>> was passed in "..." i.e. something like
>>
>> foo1 <- function(x, ...)
>> {
>>  if(testForArgumentInThreeDots(arg1)) arg1 <- "some value"
>>  foo2(x, arg1=arg1, ...)
>> }
>>
>> Thanks!
>>
>> -- 
>> Lep pozdrav / With regards,
>>    Gregor Gorjanc
>>
>> ----------------------------------------------------------------------
>> University of Ljubljana     PhD student
>> Biotechnical Faculty
>> Zootechnical Department     URI: http://www.bfro.uni-lj.si/MR/ggorjan
>> Groblje 3                   mail: gregor.gorjanc <at> bfro.uni-lj.si
>>
>> SI-1230 Domzale             tel: +386 (0)1 72 17 861
>> Slovenia, Europe            fax: +386 (0)1 72 17 888
>>
>> ----------------------------------------------------------------------
>> "One must learn by doing the thing; for though you think you know it,
>>  you have no certainty until you try." Sophocles ~ 450 B.C.
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>


-- 
Lep pozdrav / With regards,
    Gregor Gorjanc

----------------------------------------------------------------------
University of Ljubljana     PhD student
Biotechnical Faculty
Zootechnical Department     URI: http://www.bfro.uni-lj.si/MR/ggorjan
Groblje 3                   mail: gregor.gorjanc <at> bfro.uni-lj.si

SI-1230 Domzale             tel: +386 (0)1 72 17 861
Slovenia, Europe            fax: +386 (0)1 72 17 888

----------------------------------------------------------------------
"One must learn by doing the thing; for though you think you know it,
 you have no certainty until you try." Sophocles ~ 450 B.C.