Isn't destructuring cool? We take an anonymous list and quickly associate useful names with what otherwise would be car, cadr, and caddr, etc.
In common lisp when we use destructuring-bind we can have optional /and/ keyword arguments, so you can plan ahead and create an adhoc list like (1 2 :height 3 :width 4) and let :weight default to 42:
(destructuring-bind (x y &key (height )(width 0)(weight 42))
..etc with x, y, height, width, and weight...)
Hmmm, I think I did that for my Arc implementation of defun...shuffle, shuffle, dig..ah:
(mac defun (name params . body)
(w/uniq (rtargs)
`(def ,name ,rtargs
(withs ,(with (reqs nil key? nil opt? nil keys nil opts nil without)
(each p params
(if (is p '&o) (do (assert (no opt?) "Duplicate &o:" ',params)
(assert (no key?) "&k cannot precede &o:" ',params)
(= opt? t))
(is p '&k) (do (assert (no key?) "Duplicate &k:" ',params)
(= key? t))
key? (push-end p keys)
opt? (push-end p opts)
(do (assert (~acons p) "Reqd parameters need not be defaulted:" p)
(push-end p reqs))))
(with (n -1 kvs (uniq))
(+ (mappend [list _ `(nth ,(++ n) ,rtargs)] reqs)
(mappend [list (carif _) `(or (nth ,(++ n) ,rtargs)
,(cadrif _))] opts)
(list kvs `(pair (nthcdr ,(++ n) ,rtargs)))
(mappend [list (carif _)
`(or (alref ,kvs ',(carif _))
,(cadrif _))] keys)
)))
,@body))))
