Re: AKClassHierarchy

[Gavin Kistner <gavin@...>]

On Feb 11, 2006, at 7:39 PM, David Given wrote:
> On Sunday 12 February 2006 00:41, Gavin Kistner wrote:
> [...]
> > I'm confused what you mean by this. Could you elaborate?
>
> It's the standard Python trick (which suffers from this same  
> problem). When
> you define a class, you define symbol local to the class that  
> points at your
> class' superclass (does that sentence actually make sense)? It  
> means that you
> can use clearer terminology when you call methods, and if you want  
> to change
> your class hierarchy you only need to modify one thing rather than  
> hunting
> down every place where you call your superclass.
>
> The above code is an extension of this concept where PA's defining  
> a symbol
> that points at the *current* class. Interesting idea, and possibly  
> one I'll
> think about adopting.

I am still not sure I understand how this works in a three-layer case  
like the one I posted before. Here's what I *think* was being  
suggested, in a hard-coded way.


Rectangle = {
	initialize = function( obj )
		print( "Rectangle's initializer, yay!" )
	end
}

Square = {
	initialize = function( obj )
		print( "Square's initializer" )
		obj.super.initialize( obj )
	end
}

UnitSquare = {
	initialize = function( obj )
		print( "UnitSquare's initializer" )
		obj.super.initialize( obj )
	end
}

mySquare = {
	class = Square,
	super = Rectangle
}

Square.initialize( mySquare )
--> Square's initializer
--> Rectangle's initializer, yay!


myUnitSquare = {
	class = UnitSquare,
	super = Square
}

UnitSquare.initialize( myUnitSquare )

--> UnitSquare's initializer
--> Square's initializer
--> Square's initializer
--> Square's initializer
--> Square's initializer
(4000 or so more)

lua: stack overflow
stack traceback:
	[C]: in function `print'
	/Users/gkistner/Desktop/tmp.lua:9: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	...
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:10: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:17: in function `initialize'
	/Users/gkistner/Desktop/tmp.lua:36: in main chunk
	[C]: ?