lisp 小代码1

common lisp是一种强大的语言。

 

日后在这里贴一些书上摘录或是自己写的一些小段代码.

 

(defun double (x)
  (+ x x ))

(defun ^ (&rest lst)
  (let ((sum (car lst)))
    (dolist (i (cdr lst))
      (setf sum (expt sum i)))
    sum))

(defun for-operation (fn &rest lst)
  (let ((lst (car lst)))
  (let ((sum (car lst)))
    (if (null lst) (setq sum 0))
    (dolist (i (cdr lst))
      (setq sum (funcall fn sum i)))
    sum)))

(defun my-plus (&rest lst)
  (for-operation #'+ lst))

(defun my-mil (&rest lst)
  (for-operation #'* lst))

(defun my-sub (&rest lst)
  (for-operation #'- lst))

(defun my-div (&rest lst)
  (for-operation #'/ lst))

(defun odd-obj (lst)
  (if (consp lst)
    (cons (car lst) (odd-obj (cdr (cdr lst))))
    nil))

(defun even-obj (lst)
  (if (consp (cdr lst)) 
    (cons (car (cdr lst)) (even-obj (cdr (cdr lst))))
    nil))

(setq double 4)
(print (double 3))          ;6
(print (double double))     ;8
(print (symbol-value 'double))  ;4
(print #'double)
(print (symbol-function 'double))

(print (odd-obj '(a b c d e f g h i j )))  ; A C E G I
(print (even-obj '(a b c d e f g h i j ))) ; B D F H J
(print (^ 2 3 4))  ; 4096  ( (2^3)^4  ; 2^3 == (expt 2 3) equal 8)
(print (my-plus 1 2 3 4 5 6)) 
(print (my-sub 1 2 3 4 5 6)) 
(print (my-mil 1 2 3 4 5 6)) 
(print (my-div 1 2 3 4 5 6)) 

; above write at 2011/6/8 23:16