[Newbies] Array vs OrderedCollection

Miguel Enrique Cobá Martínez miguel.coba at gmail.com
Mon Apr 27 12:12:56 UTC 2009

David T. Lewis wrote:
> On Sun, Apr 26, 2009 at 10:08:54PM -0500, Miguel Enrique Cob? Mart?nez wrote:
>> Jerome Peace wrote:
>>> Hi Miguel,
>>> The answer depends on what you are doing.
>>> Arrays are compact fixed size entities. OrderedCollections are less 
>>> compact and less fixed size.
>>> If you are building a list by adding objects to it. Don't care to know the 
>>> maximum size in advance. Or need a stack like object, OrderedCollections 
>>> are your class of object.
>>> Once you are done building. Know the exact size and know that few changes 
>>> to the list will be needed. Array is good.
>>> Many things should not care whether the collection is one or the other as 
>>> far as messages go. Performance will usually favor Arrays when the size is 
>>> not changing.
>>> So do you want random access to your collection?
>>> Or do you need to easily add or remove things from the ends?
>>> It is easy to have it both ways. When the processing favors 
>>> OrderedCollections use asOrderedCollection to insure the class.
>>> When random access rather than growth is needed use asArray.
>>> Don't care? Leave it be. Most language will work with either.
>>> Also some objects already have preferences. Streams currently expect their 
>>> contents to be Arrays.
>>> Strings expect to be arrays of Characters.
>>> I have found no I-can-plan-in-advance type rules for this. I find myself 
>>> annoyed when the code requires I actually choose.
>>> I usually aim for using Arrays. And if the code fights me on this I use 
>>> OrderedCollections.
>>> If I want a stack then I need ordered collection using addLast: item and 
>>> removeLast for push and pop. I found this out after reading Kent Beck's 
>>> book on Smalltalk best practice pattens.
>>> Yours in curiosity and service, --Jerome Peace
>> Thanks for your advise. I think that as the array is a VM-aware type, it 
>> is implemented as native code. Maybe that is not the case with the 
>> ordered colection, that is byte code compiled.
> Array is an ordinary class, just like OrderedCollection. The VM is aware
> of class Array only in the sense that it has hooks to create instances of
> Array from within the VM, but the actual instances are objects just like
> other object.
Thanks for the explanation, I had the idea that the array was internally 
something special and diferent than the other clases.

Miguel Cobá
>> But besides that, a OrderedCollection is more versatile than an Array.
>> Anyway, I think that for my code, as is more focused to adding and 
>> removing objects and for this, an OrderedCollection is the best choice.
> Yes, good choice.
> Dave
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