You might want to consider using the proto package. Otherwise,
functions that end in <- have the ability to alter their arguments.
Look at the following (admittedly not very natural) construct:
`fooModifier<-` <- function( foo, value ) {
foo$bar <- "bar"
}
fooModifier( fooStack[[ 1 ]] ) <- NULL
> fooStack
[[1]]
[1] "bar"
[[2]]
list()
[[3]]
list()
[[4]]
list()
[[5]]
list()
I agree, that it would be nice to be able to do this more easily.
Haris Skiadas
Department of Mathematics and Computer Science
Hanover College
On Jan 3, 2008, at 4:35 PM, Peter Waltman wrote:
>
> specifically, imagine we have:
>
> fooStack <- list()
> for ( i in 1:5 )
> fooStack[[i]] <- list()
>
> and we have a function:
>
> fooModifier <- function( foo ) {
>
> foo$bar <- "bar"
>
> }
>
> then, if we invoke fooModifier, i.e.:
>
> fooModifier( fooStack[[ 1 ]] )
>
> the $bar elt is only set in the scope of the function, and if we
> use the
> "<<-" modifier in fooModifier, R will throw an error b/c it
> can't find the
> "foo" object. I have to say that for someone coming from
> languages that
> have pointers and/or references, it's really frustrating that R
> fails to
> allow one to have direct access to the objects' memory space.
> Onyway, one workaround would be to pass in the whole fooStack
> object and the
> index of the elt that you want to modify to the fooModifier fn,
> but I'd
> rather not have to pass the whole thing in.
> Any suggestions?
> Thanks!
> Peter Waltman
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