> > These are obvious toy examples, but it is a real problem > > if you want to create a class that defines names or length > > in a meaningful way, that is incompatible with the > > underlying data structure. > > Yes indeed, (and "well know"). > I'm arguing that in such a situation, i.e., where you > explicitly let length() --- or `[` --- behave incompatibly > with respect to the underlying data structure, > you have to define your own str() S3 method. > > I/we have done so ourselves in quite a few cases; > typically this is a 1- or 2-liner, possibly calling > utils:::str.default(). > I do actually think we should *un*hide str.default() for such > situations.
That would be useful! > In such a case (and not only here), using an S4 class instead of > an S3 is much more natural IMO. Be that as it may, it would still be nice for str to work with S3 objects with potentially incorrect length and names methods - str is particularly useful when debugging. Part of the problem is I don't how to force internally dispatched generics to use the default case - if the generic uses regular dispatch you can always use generic.default() (or similar), but I don't think it's possible to do the same for an internal generic (without copying the object, which is obviously undesirable)? Hadley -- Chief Scientist, RStudio http://had.co.nz/ ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
