[R] Use of contains in S4 classes

[Ross Boylan]

On Thu, 2005-08-18 at 17:30 -0500, Paul Roebuck wrote:
> On Thu, 18 Aug 2005, Ross Boylan wrote:
> 
> > setClass("B", representation=representation("B", extra="numeric"))
> > setClass("B", representation=representation(extra="numeric"),
> > 	contains="B")
> > Are these the same?  If not, how do they differ?
> >
> > What about
> > setClass("B", representation=representation("B", extra="numeric"),
> > 	contains="B")
> > ?
> >
> > As far as I can tell, the Green Book doesn't talk about a contains
> > argument to setClass.
> 
> "S4 - Composition and Inheritance" by Witold Eryk Wolski
> (a.k.a. Extending.pdf) might be what you're looking for.

Thank you.  It speaks directly to this question, and asserts that the
first two forms are equivalent.  contains makes it a bit easier for the
eye to catch that inheritance is happening.