variable arguments in the middle of arglists?

[Mike Caplinger <mike@rice.ARPA>]

Suppose I define an AREF function as

(aref self . subs)

and then want to define a SETTER for it.  I then need a mandatory first
argument, a variable number of subscripts bundled in a list, and a
final argument of the new value.  But I can't define it like

((setter aref) self . subs new-val)

for obvious reasons.  Is there some stylistically cleaner way of doing
it than saying

((setter aref) self . rest)

and taking rest apart manually in a LET?  Since not even Common Lisp
has a feature like this, I can see why it was omitted, but it seems
like a fairly common thing to do.

	- Mike