You're welcome---I'm glad to have been of assistance.
As for storing copies, I would have said that it would store extra copies because of the different variable it closes over, but almkglor points out that you can separate code and environment, so the question is what mzscheme does.
The thing about redefinition is that in, say, Ruby, you can do
class String
def foo
code_goes_here
end
end
And every string will have that new foo method. Here, you can only redefine the methods of one object.
For me, the real syntax question is whether we want (until p age) (which probably means that we are using the CLOS model of generic functions) or we want (p!until age) (which probably means that we are using the Smalltalk model of message passing). I sort of like the former syntax, but I also sort of prefer the Smalltalk model. What do you think?
Note that redefinition using (p!until age) syntax is still possible in Arc using 'defcall and if you predeclare the private variables.
For instance, consider this:
(deftype foo (x)
(private y z)
(meth niaw ()
(do-something x y z))
(meth arf (something)
(do-something-else something x y z)))
=>
(let methods
(table
; lambda lifted!
'niaw
(fn (x y z)
(do-something x y z))
'arf
(fn (x y z something)
(do-something-else something x y z)))
(def foo-replace-method (s f)
(= (methods s) f))
; so external code can determine the local variables
(def foo-get-private-variables ()
'(x y z))
(def foo (x)
(with (y nil z nil)
(let invoker
(fn (f rest)
(apply f x y z rest))
(fn (which-method)
(aif
(methods which-method)
(fn rest (invoker it rest)))))))
