PREV.LSP[W81,JMC] - www.SailDart.org

perm filename PREV.LSP[W81,JMC] blob sn#559210 filedate 1981-01-23 generic text, type C, neo UTF8

COMMENT ⊗   VALID 00002 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	 In place reversal of a list - after Manna
C00003 ENDMK
C⊗;
;;; In place reversal of a list - after Manna

(defun prev (u) (prog (b tem)
		      (setq b nil)
		      loop
		      (setq tem (cdr u))
		      (rplacd u b)
		      (if (null tem) (return u))
		      (setq b u)
		      (setq u tem)
		      (go loop)))

(setq x0 nil)
(setq x1 '(a))
(setq x2 '(a b))
(setq x5 '(a b c d e))