🚀 go-pugleaf

Section 28.1.10 in the 2nd Edition of CLtL features the following:

	A class that is in an instance of STANDARD-CLASS can
	be redefined if the new class will also be an
	instance of STANDARD-CLASS.  Redefining a class
	modifies the existing class object to reflect the
	new class definition; it does not create a new class
	object for the class. [rest of paragraph omitted --
	SMC] 

	When the class C is redefined, changes are
	propogated to its instances and to instances of any
	of its subclasses.  Updating such an instance occurs
	at an implementation-dependent time, but no later
	than the next time a slot of that instance is read
	or written.  Updating an instance does not change
	its indentity as defined by the EQ function.  The
	updating process may change the slots of that
	particular instance, but it does not create a new
	instance.  Whether updating an instance comsumes
	storage is implementation-dependent.

	...

I am curious as to how the current implementations of CLOS (both
commercial and research) attempt to conform to this specification.  Is
this feature generally supported yet?  Do implementations that do
support it convert all instances at the time of class redefinition, or
"lazily"?  Are there limitations on the types of changes that can be
made to a class?


--
Stewart M. Clamen			Internet:    clamen@cs.cmu.edu
School of Computer Science		UUCP: 	     uunet!"clamen@cs.cmu.edu"
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