[Newbies] Populate a new array.

Michael van der Gulik mikevdg at gulik.co.nz
Sat Mar 17 04:36:14 UTC 2007

Bert Freudenberg wrote:

> On Mar 15, 2007, at 10:54 , Michael van der Gulik wrote:
>>> Also, observing that "at:" is actually implemented in Object,  
>>> which  seems...odd!
>> It is a bit odd. An Object in the virtual machine resembles an  array 
>> of instance variables, and that method assigns to an instance  
>> variable by number.
> Wrong. Any Squeak object is made of zero or more instance variables  
> ("named variables") plus zero or more numbered variables ("indexed  
> variables"). The difference is that the number of named variables is  
> fixed for all objects of that class, but the number of indexed  
> variables can be specified when creating an instance using #new:, so  
> it can differ from instance to instance. Object>>at: lets you access  
> those indexed variables. How else would you access these?
>> It's not often useful (and downright dangerous if you ask me)
> Huh? It provides the very basics of the system! If we Smalltalkers  
> say "everything is an Object" we mean it. Literally. There is no  
> special "array object" that is different from "regular objects".  
> Rather, you can implement an array as an object that happens to have  
> indexed variables:
> Object variableSubclass: #BertsArray
>     instanceVariableNames: ''
>     classVariableNames: ''
>     poolDictionaries: ''
>     category: 'Bert-Arrays'.
> (BertsArray new: 7) at: 5 put: 42

Thanks, Bert. I can't believe I've been Smalltalking for so many years 
and not known that! I always just assumed that arrays were some special 
case handled by the VM, like SmallIntegers.


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