The bug might be here: > is.null(expression()) [1] TRUE But > is.null(expression(NULL)) [1] FALSE
So it might look to the methods package like you're passing in a NULL value for @bar. I might argue that expression() should not be NULL (and only NULL is NULL) as I have had similar trouble trying to extend language objects to S4 classes, partially because length 0 name, call and expression objects are either not available, or in this case, handled poorly. Robert -----Original Message----- From: Duncan Murdoch [mailto:[EMAIL PROTECTED] Sent: Monday, June 06, 2005 4:58 PM To: Peter Dalgaard Cc: r-devel@stat.math.ethz.ch Subject: Re: [Rd] Bug in new() or validObject() in methods package (PR#7922) On 6/6/2005 4:55 PM, Peter Dalgaard wrote: > [EMAIL PROTECTED] writes: > >> Is it doing an extra eval or something? It looks like it: >> >> > x <- expression() >> > x >> expression() >> > eval(x) >> NULL >> > >> > x <- quote(expression()) >> > x >> expression() >> > eval(x) >> expression() >> > eval(eval(x)) >> NULL > > You do realize that the two expression() results are not identical: > >> x <- quote(expression()) >> class(x) > [1] "call" >> x <- expression() >> class(x) > [1] "expression" > > Not that I can fathom what bearing that has on the real problem... I figured they weren't identical, given that they gave different results when eval'd, but I didn't know what the difference was exactly. Thanks! Duncan ______________________________________________ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel ______________________________________________ R-devel@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
