[Cuis] Copy vs Clone

[Ken.Dickey]

I seem to recall an early Smalltalk paper (OOPSLA?) on "Creation Relations" which specifically manage share vs duplicate copy semantics.

I am most familiar with this from prototype based multimedia authoring environments.

In brief, there are cases where one wants to distinguish where ivar state is shared vs individual.

So I make a new, say automobile.  It gets its own (unshared) tires, doors, and engine but all cars manufactured by Honda share their manufacturer.

I believe this is the reason for Object's definition of #copy, which allows complete control of share/duplicate:

Object>>copy
	^self shallowCopy postCopy

I am not proposing a system which manages "creation relations" here, just pointing out the need for awareness of the Share vs Duplicate aspect of Copy/Clone semantics.

Since I am working on adding drag-n-drop behaviors to individual morphs, my usages are more prototype like.  More Self-like. 

Morph's #copy has very different semantics which basically disallows sharing:

Morph>>copy
	^ Object unStream: (ReferenceStream streamedRepresentationOf: self)  

Hence some of my inital confusion with #copy.  Same name, different semantics.
 
-- 
-KenD