(in-package "SB!C")
-;;; Each structure that may be placed in a SSet must include the
-;;; SSet-Element structure. We allow an initial value of NIL to mean
+;;; Each structure that may be placed in a SSET must include the
+;;; SSET-ELEMENT structure. We allow an initial value of NIL to mean
;;; that no ordering has been assigned yet (although an ordering must
;;; be assigned before doing set operations.)
(defstruct (sset-element (:constructor nil)
(:copier nil))
(number nil :type (or index null)))
-(defstruct (sset (:constructor make-sset ()))
- (elements (list nil) :type list))
+(defstruct (sset (:copier nil))
+ ;; The element at the head of the list here seems always to be
+ ;; ignored. I think this idea is that the extra level of indirection
+ ;; it provides is handy to allow various destructive operations on
+ ;; SSETs to be expressed more easily. -- WHN
+ (elements (list nil) :type cons))
(defprinter (sset)
(elements :prin1 (cdr elements)))
(defmacro do-sset-elements ((var sset &optional result) &body body)
`(dolist (,var (cdr (sset-elements ,sset)) ,result) ,@body))
-;;; Destructively add Element to Set. If Element was not in the set,
+;;; Destructively add ELEMENT to SET. If ELEMENT was not in the set,
;;; then we return true, otherwise we return false.
(declaim (ftype (function (sset-element sset) boolean) sset-adjoin))
(defun sset-adjoin (element set)
(setf (cdr prev) (cons element current))
(return t))))))
-;;; Destructively remove Element from Set. If element was in the set,
+;;; Destructively remove ELEMENT from SET. If element was in the set,
;;; then return true, otherwise return false.
(declaim (ftype (function (sset-element sset) boolean) sset-delete))
(defun sset-delete (element set)
(setf (cdr prev) (cdr current))
(return t)))))
-;;; Return true if Element is in Set, false otherwise.
+;;; Return true if ELEMENT is in SET, false otherwise.
(declaim (ftype (function (sset-element sset) boolean) sset-member))
(defun sset-member (element set)
(declare (inline member))
;;; Return a new copy of SET.
(declaim (ftype (function (sset) sset) copy-sset))
(defun copy-sset (set)
- (let ((res (make-sset)))
- (setf (sset-elements res) (copy-list (sset-elements set)))
- res))
+ (make-sset :elements (copy-list (sset-elements set))))
-;;; Perform the appropriate set operation on SET1 and SET2 by destructively
-;;; modifying SET1. We return true if SET1 was modified, false otherwise.
+;;; Perform the appropriate set operation on SET1 and SET2 by
+;;; destructively modifying SET1. We return true if SET1 was modified,
+;;; false otherwise.
(declaim (ftype (function (sset sset) boolean) sset-union sset-intersection
sset-difference))
(defun sset-union (set1 set2)
(if (> num1 num2)
(let ((new (cons e el1)))
(setf (cdr prev-el1) new)
- (setq prev-el1 new changed t))
+ (setq prev-el1 new
+ changed t))
(shiftf prev-el1 el1 (cdr el1)))
(return))
(shiftf prev-el1 el1 (cdr el1))))))))
(return))
(shiftf prev-el1 el1 (cdr el1))))))))
-;;; Destructively modify Set1 to include its union with the difference
-;;; of Set2 and Set3. We return true if Set1 was modified, false
+;;; Destructively modify SET1 to include its union with the difference
+;;; of SET2 and SET3. We return true if Set1 was modified, false
;;; otherwise.
(declaim (ftype (function (sset sset sset) boolean) sset-union-of-difference))
(defun sset-union-of-difference (set1 set2 set3)