[Rd] pass-by-reference

[Henrik Bengtsson]

See packages R.oo and proto.

If you wish to do it yourself, you want to utilize environments for this.

/Henrik

On Thu, Jul 8, 2010 at 6:52 AM, Paul Bailey <pdbailey at umd.edu> wrote:
>
> I'm working with a large object that I want to modify slightly in a function.
> Pass-by-reference would make a lot of sense, but I don't know how to do it.
>
> I've searched this archive and thought that I can do something like
>
> f <- function(x) {
>  v1 <- list(a=x,b=3)
>  g(x)
>  v1
> }
> g <- function(x) {
>  frame <- parent.frame()
>  assign("v1",list(a=x,b=x),frame)
> }
> f(4)
> returns list(a=4,b=4)
>
> but what if I wanted to make v1[[1]] = v1[[1]] + v1[[2]] without creating a
> copy of v1?
>
> f2 <- function(x) {
>  v1 <- list(a=x,b=3)
>  g2(x)
>  v1
> }
> g2 <- function(x) {
>  frame <- parent.frame()
>  v1 <- get("v1",envir=frame)
>  v1[[1]] <- v1[[1]] + v1[[2]]
> }
> f2(4)
>
> but this fails. (it returns list(a=4,b=3) because v1 was copied into g2, not
> passed by reference) Is there a way to do this?
> --
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>
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