On Fri, 27 Jun 2003, Philippe Grosjean wrote: > Prof. Brian Ripley wrote: > >Philippe, > > >as.list(NULL) is the same as list(), and that is what I think you should > >be using in both cases. > > OK, thank you. > > >However, I do think that either both or neither of your examples should > >work: my preference would be `neither' but as S allows both it should be > >`either'. > > I agree with you, including on the fact that 'neither' should work. I would > prefer a language that obliges to declare list components before using them.
I've altered this to work like S (and documented it). > Experimenting a little bit more around this problem, I got that: > > - assigning NULL to a list entry deletes this entry from the list. OK, fine. > Asking for: > my.list$non.existing.item gives NULL. Thus, it is consistent. However, if I > use this: > > > a <- list(item1=NULL, item2=NULL) > > a > $item1 > NULL > > $item2 > NULL > > - this is a strange behaviour because the previous command should have > returned 'list()' in a. Consequently, when I reallocate NULL to either > 'item1', or 'item2' of 'a', it deletes it: > > > a$item1 <- NULL > > a > $item2 > NULL > > Not an harmfull behaviour, but inconsistent with the rest. It is in the FAQ, though. -- 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 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help
