Re: structs, records, SMOBs etc.

[Jost Boekemeier <jostobfe@calvados.zrz.TU-Berlin.DE>]

> We're going to implement an object system on top of the structs.  When
> we've replaced the structs, the object system can work on top of the
> new representation.


Why do you want to implement an object system on top of ("C") structures?
An object is just a (expandable) set of "features", where a "feature"
is either a state variable or code. An example from Meyer's OOSC:

(define comparable (object () ; import from: no superclass
			   (le minimum value); interface: we export 3 features
			   (
			   ; le is deferred
			    (minimum (lambda (other) (if (le other) value (other value))))
			    (value) ;abstract
			    )))

Now the class "int-comparable" is derived from comparable and overrides le 
(position 1):

(define int-comparable (object (comparable)
			       (le minimum value)
			       (
				(le (lambda () (<= value (other value)))))))


We can now use this concrete class "int-comparable" and create objects
by sending it a message:

(define i (int-comparable value 10))
(define j (int-comparable value 9))
(i minimum j) -> 9


I think an object is just a vector of name/value pairs, not a structure!



Jost