On Tue, 13 Nov 2007, "Jens Oehlschlägel" wrote:
Thank you Brian,
setReplaceMethod() is just syntactic sugar for setting an S4 method on a
replacement function (read the function definition to see so). You can
set S3 replacement methods, and the S4 mechanism just piggy-backs on that.
So I understand that setReplaceMethod will not help.
I think the conceptual problem is that the assignment operator does not
actually do any copying: it creates a binding of a symbol to a value.
Any copying which occurs happens when the value is (potentially) changed.
I would be even happier if the cloning would only occur on any attempt to
change the external pointer / proxy-object.
There is no provision for that to depend on the class (rather than the
type) of the object.
Mh, unless the internal copying mechanism would call a clone generic for
non-atomic objects
But as I said, there is no provision for that. Nor is there going to be.
One reason is performance, as Simon has hinted. Another is consistency:
duplication might well be called from places where class is being ignored.
Since external pointers are never duplicated, you
ought to be able to take advantage of that to design the copying semantics
you want.
How that? How do I know that any user has assigned/modified the external
pointer (or a proxy object containing the external pointer) such that I can
invoke the cloning?
I don't even know what you want to do. But I don't think copying is the
place to find out if a user changed an object: presumably it was done via
your interface.
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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