thanks boris
I will digest that.
On 19 sept. 04, at 18:07, Boris Gaertner wrote:

>
> "stéphane ducasse" <ducasse at iam.unibe.ch> wrote:
>
>
>> Hi all
>>
>> I'm checking whether my VW slides are working in Squeak and....huge
>> disappointment.
>> for example:
>>
>> |st|
>> st := ReadWriteStream on: (OrderedCollection new: 5).
>> st nextPut: 1.
>> st contents.
>>
>> works perfectly in VW and breaks in Squeak.
> Well, I often found it unconvenient that I cannot have
> a WriteStream streaming over an OrderedCollection, but
> I got accustumed to use an Array.
>
>> What is the reason for such a difference?
> The fact that  size has a different meaning for OrderedCollections and
> Arrays.
> (ar := Array new: 10) size  = 10
> (oc := OrderedCollection new: 10) size = 0.
> (str := String new: 10) size = 10.
>
> The consequence of this difference is that
> you can evaluate:
>   ar at: 1 put: #foo
>   str at: 1 put: $f
> but for
> oc at: 1 put: #foo
> you get an index out ouf bounds error.
>
> All this is also true for VW.
> So, why can VW write into a Stream over an OrderedCollection
> while Squeak cannot? The answer is not difficult, but it takes some
> time to verify it from the code.
> Here is what I found:
>
> *The protocol of a WriteStream includes the capability to grow
> a collection when it is full. In Squeak we simply create a larger 
> collection
> and copy the contents of the smaller collection into the larger one.
> For an Array, the grown collection has a largersize, but for
> an OrderedCollection, the size of the grown collection is that of
> the smaller collection.
> *In VW,  they do it smarter: When they grow an OrderedCollection,
> they initialize all not immediately needed elements with nil.
> That is the difference and of course we can do that too, if we
> want to have it.
>
> Attached you find a proposal to implement collection growing with
> initialization of those collections that are not implemented as
> variable classes. This change set is dangerous and requires
> very careful testing.
>
>
>
>> Why can I put an OrderedCollection in a stream?
> See explanation above.
>
>>
>> |st|
>> st := ReadWriteStream on: (Array new: 5).
>> st nextPut: 1.
>> st contents.
>>
>> works on both VW and Squeak
>>
>
> Greetings, Boris
> <growAndInitCollections.1.cs>