增强的NTH函数

marting

1. ;;  CAB  10/15/2005
   
2. ;;+++++++++++++++++++++++++++++++++++++++++++++++++++++
   
3. ;;  Return a sub list starting at the nth position and
   
4. ;;  with the number of items specified by num
   
5. ;;+++++++++++++++++++++++++++++++++++++++++++++++++++++
   
6. (defun nth+ (idx ; start position 0 = first item
   
7.              lst ; list of items
   
8.              num ; number of items to return
   
9.              ;;    0= all remaining items
   
10.              / newlst)
    
11.   (and (or (numberp num) ; catch non numbers
    
12.            (setq num 0)) ; force all
    
13.        (zerop num) ; if zero
    
14.        (setq num (length lst)) ; all
    
15.   )
    
16.   (repeat num
    
17.     (setq newlst (cons (nth idx lst) newlst)
    
18.           idx (1+ idx))
    
19.   )
    
20.   (reverse (vl-remove nil newlst))
    
21. )
    

;;  CAB  10/15/2005<br /> ;;+++++++++++++++++++++++++++++++++++++++++++++++++++++<br /> ;;  Return a sub list starting at the nth position and<br /> ;;  with the number of items specified by num<br /> ;;+++++++++++++++++++++++++++++++++++++++++++++++++++++<br /> (defun nth+ (idx ; start position 0 = first item<br />              lst ; list of items<br />              num ; number of items to return<br />              ;;    0= all remaining items<br />              / newlst)<br />   (and (or (numberp num) ; catch non numbers<br />            (setq num 0)) ; force all<br />        (zerop num) ; if zero<br />        (setq num (length lst)) ; all<br />   )<br />   (repeat num<br />     (setq newlst (cons (nth idx lst) newlst)<br />           idx (1+ idx))<br />   )<br />   (reverse (vl-remove nil newlst))<br /> )<br />

1. (defun c:tt()
   
2.   (print (nth+ 0 '(1 2 3 4 5) 2)) ; |-> (1 2)
   
3.   (print (nth+ 3 '(1 2 3 4 5) 2)) ; |-> (4 5)
   
4.   (print (nth+ 4 '(1 2 3 4 5) 5)) ; |-> (5)   
   
5.   (print (nth+ 6 '(1 2 3 4 5) 2)) ; |-> nil   
   
6.   (print (nth+ 2 '(1 2 3 4 5) 0)) ; |-> (3 4 5)
   
7.   (princ)
   
8. )
   

(defun c:tt()<br />   (print (nth+ 0 '(1 2 3 4 5) 2)) ; |-> (1 2) <br />   (print (nth+ 3 '(1 2 3 4 5) 2)) ; |-> (4 5) <br />   (print (nth+ 4 '(1 2 3 4 5) 5)) ; |-> (5)   <br />   (print (nth+ 6 '(1 2 3 4 5) 2)) ; |-> nil   <br />   (print (nth+ 2 '(1 2 3 4 5) 0)) ; |-> (3 4 5)<br />   (princ)<br /> )<br />

renyonghua2014

实用，谢谢提供。