Thanks Hendrik. My main concern is that it should not be so easy to crash R. On whether or not NextMethod from within the default method is kosher or not - I would have thought so, but clearly I'm wrong here. Perhaps NextMethod within a default method should be something that at least attracts a warning. Regards, Bill Venables, CMIS, CSIRO Laboratories, PO Box 120, Cleveland, Qld. 4163 AUSTRALIA Office Phone (email preferred): +61 7 3826 7251 Fax (if absolutely necessary): +61 7 3826 7304 Mobile (rarely used): +61 4 1963 4642 Home Phone: +61 7 3286 7700 mailto:Bill.Venables at csiro.au http://www.cmis.csiro.au/bill.venables/ -----Original Message----- From: Henrik Bengtsson [mailto:hb at maths.lth.se] Sent: Wednesday, 21 December 2005 1:48 PM To: Venables, Bill (CMIS, Cleveland) Cc: r-devel at stat.math.ethz.ch; R-bugs at biostat.ku.dk Subject: Re: [Rd] NextMethod causes R 2.2.0 to crash (PR#8416)
Bill.Venables at csiro.au wrote:
I found writing the following default method the for the generic
function "julian" causes R to crash.
julian.default <- function(x, ...) {
x <- as.Date(x)
NextMethod("julian", x, ...)
}
On Windows XP R 2.2.0 Patched (2005-11-21 r36410) you get:
Error: evaluation nested too deeply: infinite recursion /
options(expressions=)?
and on Windows XP R 2.1.1 Patched (2005-09-19) you get:
Error: protect(): protection stack overflow
It seems that the R.2.2.0 revision you have does not protect against
this. I agree that it should not be possible to crash R, but is it
valid to call NextMethod() in a default function? [R core, should this
ever be allowed?]
I do not know exactly how NextMethod() is expected to work here, but I
could imaging that 'x' has class 'Date' when NextMethod() is called and
the "next" class will the be the default one so you call
julian.default() again ending up in an infinite call. This makes sense
from the errors I get above. Try this and see what you get in your
version:
julian.default <- function(x, ...) {
cat("In julian.default()\n")
x <- as.Date(x)
NextMethod("julian", x, ...)
}
Was you intention to do the following instead
julian.default <- function(x, ...) {
x <- as.Date(x)
julian(x, ...)
}
where julian() is the generic function?
Cheers
Henrik
Here is a test example
m <- as.Date("1972-09-27") + 0:10
m
[1] "1972-09-27" "1972-09-28" "1972-09-29" "1972-09-30" "1972-10-01" "1972-10-02" "1972-10-03" [8] "1972-10-04" "1972-10-05" "1972-10-06" "1972-10-07"
class(m)
[1] "Date"
julian(m)
[1] 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 attr(,"origin") [1] "1970-01-01"
m <- as.character(m) class(m)
[1] "character"
julian(m)
< R crashes> --please do not edit the information below-- Version: platform = i386-pc-mingw32 arch = i386 os = mingw32 system = i386, mingw32 status = major = 2 minor = 2.0 year = 2005 month = 10 day = 06 svn rev = 35749 language = R Bill Venables, CMIS, CSIRO Laboratories, PO Box 120, Cleveland, Qld. 4163 AUSTRALIA Office Phone (email preferred): +61 7 3826 7251 Fax (if absolutely necessary): +61 7 3826 7304 Mobile (rarely used): +61 4 1963 4642 Home Phone: +61 7 3286 7700 mailto:Bill.Venables at csiro.au http://www.cmis.csiro.au/bill.venables/
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