🚀 go-pugleaf

Andy Belk writes
> Hi all.
>         Just as an aside, this (List->Stack) is a fairly good example of
> when subclassing is not necessarily what is really desired.
> 
> A Stack usually has push and pop operations, and in this case also a display
> method, but one can argue that doing List operations on a stack may cause
> problems. For example, one can do things that mess up the LIFO idea of a
> stack:
> 
> Stack s;
> Integer i = 5;
> [s init];
> [s push: i--];
> [s push: i--];
> [s push: i--];
> [s push: i--];
> [s push: i--];
> [s removeObjectAt: 5];   // Ok, you can do it, but should you be able to ?
> [[s pop] display];
> 
> etc.
[rest deleted]

An excerpt from Object.rtf from the NextDocumentation:

.... For example, an Object subclass might renounce the copy method by reimplementing it to include an error: message as follows:

- copy
{
    [self error:"  %s objects should not be sent '%s' messages\n",
            [[self class] name], sel_getName(_cmd)];
}

This code prevents instances of the subclass from recognizing or forwarding copy messageslthough the respondsTo: method will still report that the receiver has access to a copy method. .....

--
			Tschoe'wa
_______________________________________
Hartmut Benz                          | benz@infko.uni-koblenz.de
D-5400 Koblenz, Germany               |       (NeXTmail ok)