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From: gunter@netcom14.netcom.com (Mike Gunter)
Subject: Re: what are abstract classes?
In-Reply-To: derway@ndc.com's message of 12 Jun 1995 18:16:36 GMT
Message-ID: <GUNTER.95Jun12135045@netcom14.netcom.com>
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References: <v02120d01ac00c0662e79@[192.124.144.135]> <DERWAY.95Jun12111637@alumni.ndc.com>
Date: Mon, 12 Jun 1995 20:50:44 GMT
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In article <DERWAY.95Jun12111637@alumni.ndc.com> derway@ndc.com (D. Erway) writes:

   So, what is the language mechanism for specifying the default concrete class
   for an abstract class?

From TFM, i.e. the DIRM (available somewhere under http://legend.gwydion.cs.cmu.edu:8001/dylan/):

	
    make class  #key #all-keys => instance	[Generic Function]
    
    ...
    
    
    The object returned is guaranteed to be a general instance of class
    but not necessarily a direct instance of class.  This liberality
    allows make to be called on an abstract class; it can instantiate and
    return a direct instance of one of the concrete subclasses of the
    abstract class.
    
    ...
    
    
    Programmers may customize make for particular classes by defining
    methods specialized by singleton specializers.  These methods may
    obtain the default make behavior, if desired, by calling next-method.
    
    ...
    
    
     The default method for make does the following:
    
    It signals an error if class is abstract.  An instantiable abstract
    class must override this method with its own method for make.



BTW, can anyone tell me/us how long the DIRM will be the manual?  (I.e.
when will the next version be out?)

	mike

