Thanks for the report. This is now fixed in R-devel and R-patched
by increasing NAMED on the RHS value to 2 when it is not 0.
Best,
luke
On Tue, 8 Jan 2013, Justin Talbot wrote:
In R version 2.15.2 (2012-10-26) i386-apple-darwin9.8.0/i386 (32-bit) I get
the following:
a <- list(1)
(a[[1]] <- a)
[[1]]
[[1]][[1]]
[1] 1
but
a <- list(1)
b <- a
(a[[1]] <- a)
[[1]]
[1] 1
And similarly:
a <- list(x=1)
(a$x <- a)
$x
$x$x
[1] 1
but
a <- list(x=1)
b <- a
(a$x <- a)
$x
[1] 1
In both cases the result of the first sequence is wrong. It's returning the
updated `a` rather than the RHS of the assignment. The second sequence in
both cases is correct; the assignment to `b` increments the NAMED value
causing the necessary copy to be made so the RHS is returned from the
assignment.
Would it be sufficient to add a check to do_subassign2_dflt
and do_subassign3_dflt that creates a duplicate of the LHS if the LHS & RHS
are the same object?
Justin
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Luke Tierney
Chair, Statistics and Actuarial Science
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
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