Dear all,
I have a question about R's modification in place and replacement functions.
I was working through Hadley Wickham's Advanced R section on
Replacement Functions and
in a file (say test.R) I wrote:
`second<-` <- function(x, value) {
x[2] <- value
x
}
x <- 1:10
second(x) <- 5L
print(x)
library(pryr)
x <- 1:10
print(address(x))
second(x) <- 6L
print(address(x))
x <- 1:10
print(address(x))
x[2] <- 7L
print(address(x))
When I copy-paste the code the effect is as expected:
> `second<-` <- function(x, value) {
+ x[2] <- value
+ x
+ }
> x <- 1:10
> second(x) <- 5L
> print(x)
[1] 1 5 3 4 5 6 7 8 9 10
>
> library(pryr)
> x <- 1:10
> print(address(x))
[1] "0x1b44ef40"
> second(x) <- 6L
> print(address(x))
[1] "0x1f955a38"
> x <- 1:10
> print(address(x))
[1] "0x1b447090"
> x[2] <- 7L
> print(address(x))
[1] "0x1b447090"
However, when I source the code the effect is a bit surprising:
> source("test.R")
[1] 1 5 3 4 5 6 7 8 9 10
[1] "0x2f372320"
[1] "0x2f394888"
[1] "0x1b446ef0"
[1] "0x1f960f30"
Notice, that the last two addresses are different.
I would be grateful if somebody could point me to an explanation for this.
I have tried this on: R version 3.1.2 running on openSUSE 12.1, R
version 3.4.2 running on openSUSE Leap 42.3
and on R running on a friend's Mac.
Thank you
Best wishes
Krzysztof Bartoszek
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