On Fri, Feb 20, 2015 at 5:48 AM, Clément Bera <bera.clem...@gmail.com>
wrote:
> It depends on your OrderedCollection implementation.
>
> OrderedCollection has a variable size in memory. When instantiated, it has
> for example 10 slots, and if you have more than 10 objects, it needs to
> change its size to hold more slots.
>
>
I thought that was the case too, but I cannot find in code what you say.
OrderedCollection nor it's parents are created with #variableSubclass... As
you can see, "OrderedCollection isVariable" answers false. So where is that
"variable size in memory" ?
Thanks,
> The current implementation relies on an indirection to an array, when the
> array overflows, the orderedCollection allocates a new bigger array and
> copy the slots from the existing array. There are some heuristics on array
> size to avoid having to grow the array too often.
>
> If you want the shallowCopy to work, you have to use the old
> implementation of OrderedCollection, which encodes in its field directly
> the values it holds. In this case however when the collection overflows you
> create a new orderedCollection so you need to use #become: to migrate
> references to the old orderedCollection to the new one. This used to be a
> bad idea because the become primitive was slow, but since we have Spur, it
> may be relevant to look at it again. This old implementation is more memory
> efficient too.
>
> 2015-02-20 8:05 GMT+01:00 Marcus Denker <marcus.den...@inria.fr>:
>
>>
>> On 20 Feb 2015, at 06:23, S Krish <krishnamachari.sudha...@gmail.com>
>> wrote:
>>
>>
>> I presumed shallowCopy for literal arrays / OrderedCollection should have
>> been a true copy. Perhaps need to understand this..
>>
>>
>> OrderdCollection is not just one object, but it holds on to an Array that
>> has it’s content. You copy the outside collection object, but share
>> the Array.
>>
>> shallowCopy
>> "Answer a copy of the receiver which shares the receiver's instance
>> variables. It should never be overridden. I'm invoked from the copy
>> template method. Subclasses that need to specialize the copy should
>> specialize the postCopy hook method."
>> ...
>> <primitive: 148>
>> class := self class.
>> class isVariable
>> ifTrue:
>> [... newObject :=* class basicNew: index*. ....]
>> ifFalse: [newObject := *class basicNew*].
>> ..
>> whileTrue:
>> [newObject instVarAt: index put: (self instVarAt: index).
>> ...
>> ^ newObject
>>
>> On Wed, Feb 18, 2015 at 10:52 PM, Marcus Denker <marcus.den...@inria.fr>
>> wrote:
>>
>>>
>>> On 18 Feb 2015, at 18:13, Cameron Sanders via Pharo-users <
>>> pharo-users@lists.pharo.org> wrote:
>>>
>>>
>>> *Date: *18 Feb 2015 18:12:33 CET
>>> *Subject: **i feel dumb / Pharo3 > OrderedCollection >> do:*
>>> *From: *Cameron Sanders <camsand...@aol.com>
>>> *To: *Any question about pharo is welcome <pharo-users@lists.pharo.org>
>>>
>>>
>>> I must be making some silly error here that i cannot see clearly. Why
>>> does the following leave anything in the list 'a'? Run it in a workspace.
>>> With or without the shallowCopy, i am left with a list with half of the
>>> elements in it. Always half.
>>>
>>> This version of Pharo3 (21.0) was downloaded last week. I am running on
>>> a Mac.
>>>
>>> Thanks in advance. ... Maybe I just need more coffee.
>>> -Cam
>>>
>>> | a |
>>> a := { #a. #b. #c. #d. } asOrderedCollection.
>>> a shallowCopy do: [ :item | (a includes: item) ifTrue: [ a remove: item
>>> ]].
>>> a size
>>>
>>>
>>> shallowCopy is not enough… OrderedCollection is made up of an internal
>>> array.
>>>
>>> #copy does the right thing, just copies the array:
>>>
>>> postCopy
>>> array := array copy
>>>
>>> and for Array, copy is a shallowCopy.
>>>
>>> Marcus
>>>
>>>
>>>
>>>
>>
>>
>
--
Mariano
http://marianopeck.wordpress.com
