Path: utzoo!mnetor!tmsoft!dptcdc!jarvis.csri.toronto.edu!mailrus!ames!amdcad!sun!pitstop!sundc!seismo!uunet!mcvax!cernvax!olsen!franco
From: franco@olsen.UUCP (Franco Monti)
Newsgroups: comp.lang.c++
Subject: Smalltalk-80 like inheritance in C++ possible ?
Message-ID: <110@honold.UUCP>
Date: 3 Mar 89 18:36:11 GMT
Reply-To: franco@honold.UUCP (Franco Monti)
Organization: Olsen & Associates, Zurich, Switzerland
Lines: 82



Hi,

Allow me a question which may be trivial for you guys. I'm a
beginner of C++ and therefore interested in the following 
flavour of inheritance:

    In Smalltalk-80 you can use inheritance as in this sample program:

    (***********************************)

    class name       One
    superclass       Object
    instance methods 

	test
	    ^1     
        
	result1
	    ^self test


    class name       Two
    superclass       One
    instance methods 

	test
	    ^2     
        

    class name       Three
    superclass       Two
    instance methods 

	result2
	    ^self  result1
	result3
	    ^super test


   (*************************************)

   Now create new instances:
 
    example1 <- One new
    example2 <- Two new
    example3 <- Three new

    and consider scenarios like this:

    expression           result
    ----------           ------

    example1 test          1
    example1 result1       1 
    example2 test          2 
    example2 result1       2 
    example3 test          2 
    example3 result2       2 
    example3 result3       2



    Now comes the tricky part: How can I translate the behavior of
    the code outline above to the appropiate structures in C++ ?
    How do you move *up and down* in a given class hierarchy,
    like in my little example, using C++ ?

    Is it possible to cover this examples with an easy to understand and well
    structured program in C++, how is this best done ?

    Could anybody give me a pointer ?

    Thanx

    Franco M. Monti
    Olsen & Associates 
    Seefeldstr. 233
    8008 Zuerich

    Switzerland