ref: 2b34bcfbd3881d039ec43becdaf61fc3171ada29
dir: /attic/plists.lsp/
; property lists. they really suck.
(setq *plists* nil)
(defun symbol-plist (sym)
(cdr (or (assoc sym *plists*) '(()))))
(defun set-symbol-plist (sym lst)
(let ((p (assoc sym *plists*)))
(if (null p) ; sym has no plist yet
(setq *plists* (cons (cons sym lst) *plists*))
(rplacd p lst))))
(defun get (sym prop)
(let ((pl (symbol-plist sym)))
(if pl
(let ((pr (member prop pl)))
(if pr (cadr pr) nil))
nil)))
(defun put (sym prop val)
(let ((p (assoc sym *plists*)))
(if (null p) ; sym has no plist yet
(setq *plists* (cons (list sym prop val) *plists*))
(let ((pr (member prop p)))
(if (null pr) ; sym doesn't have this property yet
(rplacd p (cons prop (cons val (cdr p))))
(rplaca (cdr pr) val)))))
val)