pass-by-reference

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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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?
--
View this message in context: http://r.789695.n4.nabble.com/pass-by-reference-tp2281802p2281802.html
Sent from the R devel mailing list archive at Nabble.com.

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?
--
View this message in context: http://r.789695.n4.nabble.com/pass-by-reference-tp2281802p2281802.html
Sent from the R devel mailing list archive at Nabble.com.