On 11.01.2012 18:49, Simon Urbanek wrote:
On Jan 11, 2012, at 12:08 PM, Taylor Arnold wrote:
R-devel,
I have noticed that making a copy of an object in R prior to using
.Call on the original object can
cause the C code to alter not only the object passed to it but also
the copy in R.
Please see the docs - .Call does *NOT* have a DUP argument - you are
responsible for duplication at all times if you make modifications (e.g. using
duplicate()).
Cheers,
Simon
A simple example
is:
x<- 2
y<- x
.Call("addOne", x, DUP=TRUE) # Changing DUP does not alter output
NULL
x
[1] 3
y
[1] 3
And corresponding simple C code:
"test.c":
#include<R.h>
#include<Rinternals.h>
#include<Rmath.h>
SEXP addOne(SEXP input) {
REAL(input)[0] = REAL(input)[0] + 1;
return R_NilValue;
}
I assume that this is simply a result of lazy loading
In addition to Simon: it is "lazy evalution" rather than lazy loading in
this case.
Uwe
in R, and well
documented. My question is, do
there exist functions to (1) force R to make a copy of an object
(force() does not work), and (2) to check
whether two objects are actually pointing to the same memory address.
For question 1, I have
found specific operations which force a copy of a given datatype, but
would prefer a more general
solution.
Thank you,
Taylor
sessionInfo()
R version 2.14.1 (2011-12-22)
Platform: x86_64-apple-darwin9.8.0/x86_64 (64-bit)
locale:
[1] en_GB.UTF-8/en_GB.UTF-8/en_GB.UTF-8/C/en_GB.UTF-8/en_GB.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] tools_2.14.1
--
Taylor B. Arnold
Department of Statistics
Yale University
24 Hillhouse Avenue
New Haven, CT 06520
e-mail: taylor.arn...@yale.edu
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