Ninety-Nine Lisp Problems

l99.lisp

;; http://www.ic.unicamp.br/~meidanis/courses/mc336/2006s2/funcional/L-99_Ninety-Nine_Lisp_Problems.html
;;
;; trying to use only these sacred symbols
;; (quote, atom, eq, car, cdr, cons and cond)

(defvar s '(a b c d))

(defun my-last (l)
  (if (cdr l)
      (my-last (cdr l))
      l))

(defun my-but-last (l)
  (if (cddr l)
      (my-but-last (cdr l))
      l))

(defun my-nth (l i)
  (if (= i 0)
      (car l)
      (my-nth (cdr l) (- i 1))))

(defun my-length (l)
  (if (null l)
      0
      (+ 1 (my-length (cdr l)))))

(defun my-reverse (l)
  )