surprising behaviour of names<-
Simon Urbanek wrote:
On Mar 11, 2009, at 10:52 , Simon Urbanek wrote:
Wacek, Peter gave you a full answer explaining it very well. If you really want to be able to trace each instance yourself, you have to learn far more about R internals than you apparently know (and Peter hinted at that). Internally x=1 an x=c(1) are slightly different in that the former has NAMED(x) = 2 whereas the latter has NAMED(x) = 0 which is what causes the difference in behavior as Peter explained. The reason is that c(1) creates a copy of the 1 (which is a constant [=unmutable] thus requiring a copy) and the new copy has no other references and thus can be modified and hence NAMED(x) = 0.
Errata: to be precise replace NAMED(x) = 0 with NAMED(x) = 1 above -- since NAMED(c(1)) = 0 and once it's assigned to x it becomes NAMED(x) = 1 -- this is just a detail on how things work with assignment, the explanation above is still correct since duplication happens conditional on NAMED == 2.
i guess this is what every user needs to know to understand the behaviour one can observe on the surface? thanks for further clarifications. vQ