> Generally the idea is that the class should be stripped because R has no > way of knowing if the new object, for example unique(obj), still has the > necessary properties to be considered to be of the same class as obj. > Only the author of the class knows that. S4 would help a bit here, but > only structurally (it could detect when the object couldn't possibly be > of the right class), not semantically.
There are two possible ways that S3 methods could handle subclasses: * preserve by default (would also have preserve all attributes) * drop by default If you could really on either system consistently, I think you could write correct code. It's very hard when the defaults vary. (In other words, I agree with everything you said, except I think if the default was to preserve you could still write correct code) Hadley -- http://had.co.nz/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
