Use of contains in S4 classes
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.