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Use of contains in S4 classes

4 messages · Paul Roebuck, Ross Boylan

Ross Boylan
# 
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.
Paul Roebuck
#
On Thu, 18 Aug 2005, Ross Boylan wrote:

            

      
      
      
    

        
"S4 - Composition and Inheritance" by Witold Eryk Wolski
(a.k.a. Extending.pdf) might be what you're looking for.

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      Ross Boylan
    

    

      
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Oops, the second class should have been A in the examples.  Corrected
version:

setClass("B", representation=representation("A", extra="numeric))
setClass("B", representation=representation(extra="numeric"),
	contains="A")
Are these the same?  If not, how do they differ?

What about
setClass("B", representation=representation("A", extra="numeric"),
	contains="A")
?

As far as I can tell, the Green Book doesn't talk about a contains
argument to setClass.

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Ross Boylan
    

    

      
      #
    

  


  

      
On Thu, 2005-08-18 at 17:30 -0500, Paul Roebuck wrote:

            

      
      
      
    

        
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.