[Cuis] Copy vs Clone

[Juan Vuletich]

On 5/14/2015 12:22 AM, David T. Lewis wrote:
> On Wed, May 13, 2015 at 11:24:09PM -0300, Juan Vuletich wrote:
>> Does anybody know why #clone was added to Squeak?
>>
> I do not know the historical background, but Object>>clone invokes #primitiveClone
> in the VM. This is an efficient shallow copy, in which the object header and data
> fields are copied to a newly allocated object, and the object hash and GC bits
> are updated in the new copy.
>
> I think that this must have been done for efficiency, to provide the fastest
> possible means of shallow copying an object. The methods in the VM and in Object
> are both old enough that they had no author initials, so this was a very early
> optimization in Squeak.
>
> Dave

Thanks Dave.

I searched a bit more and found 
http://lists.squeakfoundation.org/pipermail/vm-dev/2014-February/014683.html 
and the more detailed 
http://lists.gforge.inria.fr/pipermail/pharo-project/2010-January/019801.html 
(by Levente).

After these references, I decided to remove #clone from Cuis. Most 
senders were replaced by sends to #shallowCopy (it uses the same VM 
primitive). But for several, calling #copy works the same, and #copy 
sounds more natural to me. I also refactored several implementations of 
#copy et al, in SequenceableCollection and AbstractSound hierarchies. 
Will commit to github soon.

Cheers,
Juan Vuletich