nalist-to-plist.lisp

(defun nalist-to-plist (list)
  "連想リストをプロパティリストに変換する[破壊的]."
  (if (null list)
      nil
      (let ((car (car list))
            (cdr (cdr list)))
        (rplaca list (car car))
        (rplacd list car)
        (rplaca (cdr list) (cdr car))
        (rplacd (cdr list) cdr)
        (nalist-to-plist (nthcdr 2 list))
        list)))

(nalist-to-plist '((foo . 1) (bar . 2) (baz . 3)))
;;=> (foo 1 bar 2 baz 3)

(prog ((data (loop :repeat 10000 :collect (cons 1 2))))
   (time (nalist-to-plist data)))
;;=> NIL
#|
Evaluation took:
  0.001 seconds of real time
  0.000000 seconds of total run time (0.000000 user, 0.000000 system)
  0.00% CPU
  853,799 processor cycles
  0 bytes consed
  ~~~~~~~~~~~~~~
|#

(defun nplist-to-alist (list)
  "プロパティリストを連想リストに変換する[破壊的]."
  (if (null (cdr list))
      nil
      (let ((x (car list))
            (y (car (cdr list))))
        (rplaca list (cdr list))
        (rplacd list (cdr (cdr list)))
        (rplaca (car list) x)
        (rplacd (car list) y)
        (nplist-to-alist (cdr list))
        list)))

(nplist-to-alist '(foo 1 bar 2 baz 3))
;;=> ((foo . 1) (bar . 2) (baz . 3))

(prog ((data (loop :repeat 100000 :collect (cons 1 2))))
   (time (nplist-to-alist data)))
;;=> NIL
#|
Evaluation took:
  0.006 seconds of real time
  0.004000 seconds of total run time (0.004000 user, 0.000000 system)
  66.67% CPU
  7,906,917 processor cycles
  0 bytes consed
  ~~~~~~~~~~~~~~
|#