Basically as a result of all the bells and whistles source() supports
it ends up creating an additional reference to the value of each top
level expression. That forces a duplicate.
Best,
luke
On Sun, 13 May 2018, Krzysztof Bartoszek wrote:
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
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
--
Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa Phone: 319-335-3386
Department of Statistics and Fax: 319-335-3017
Actuarial Science
241 Schaeffer Hall email: luke-tier...@uiowa.edu
Iowa City, IA 52242 WWW: http://www.stat.uiowa.edu
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
