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Diffstat (limited to 'list-functions-2.lisp')
-rw-r--r-- | list-functions-2.lisp | 20 |
1 files changed, 19 insertions, 1 deletions
diff --git a/list-functions-2.lisp b/list-functions-2.lisp index caa5a58..57e3976 100644 --- a/list-functions-2.lisp +++ b/list-functions-2.lisp @@ -20,7 +20,7 @@ (export '(copy-tree assoc assoc-if assoc-if-not rassoc rassoc-if rassoc-if-not sublis nsublis mapcar mapcan mapcon acons - reverse nreverse maplist)) + reverse nreverse maplist nthcdr last nth)) (defun copy-tree (tree) @@ -128,7 +128,25 @@ (sys::cons (sys::car objects) (sys::cdr objects)) nil)) +(defun dotted-length (list) + (if (consp list) + (1+ (dotted-length (cdr list))) + 0)) + (defun length (list) (if list (%1+ (length (cdr list))) 0)) + +(defun last (list &optional (n 1)) + (let ((l (dotted-length list))) + (nthcdr (- l n)))) + +(defun nthcdr (n list) + (check-type n (integer 0)) + (if (zerop n) + list + (nthcdr (1- n) (cdr list)))) + +(defun nth (n list) + (car (nthcdr n list))) |