[LISP函数-点]：两点的中点

eachy

2. 
   
3. (defun xd-mid_point (p1 p2)
   
4.   (mapcar '(lambda (x) (/ x 2)) (mapcar '+ p1 p2))
   
5. )

<br /> (defun xd-mid_point (p1 p2)<br />   (mapcar '(lambda (x) (/ x 2)) (mapcar '+ p1 p2))<br /> )

doubao

如果想用取两点间的中点的程序作为一种捕捉方式，得用反应器，程序如下： （引自帖子“如何让程序计算出的点优先于捕捉点？”）

2. 
   
3. (defun recover_snap ( reactor_object lisp_list / )
   
4.         (setvar "osmode" $$mpt_osmode)
   
5.         (vlr-remove $$mptReactor)
   
6. )
   
7. 
   
8. (defun mpt ( / a b mx my mz )
   
9.         (while (not (setq a (getpoint "\nFirst Point : "))))
   
10.         (while (not (setq b (getpoint a "\nSecond Point: "))))
    
11.         (setq mx (/ (+ (car b) (car a)) 2.0))
    
12.         (setq my (/ (+ (cadr b) (cadr a)) 2.0))
    
13.         (setq mz (/ (+ (caddr b) (caddr a)) 2.0))
    
14.         (setq $$mpt_osmode (getvar "osmode"))
    
15.         (setvar "osmode" 0)
    
16.         (setq $$mptReactor (vlr-lisp-reactor data '((:vlr-lispEnded . recover_snap))))
    
17.         (setq pt (list mx my mz))
    
18. )

<br /> (defun recover_snap ( reactor_object lisp_list / )<br />         (setvar "osmode" $$mpt_osmode)<br />         (vlr-remove $$mptReactor)<br /> )<br /> <br /> (defun mpt ( / a b mx my mz )<br />         (while (not (setq a (getpoint "\nFirst Point : "))))<br />         (while (not (setq b (getpoint a "\nSecond Point: "))))<br />         (setq mx (/ (+ (car b) (car a)) 2.0))<br />         (setq my (/ (+ (cadr b) (cadr a)) 2.0))<br />         (setq mz (/ (+ (caddr b) (caddr a)) 2.0))<br />         (setq $$mpt_osmode (getvar "osmode"))<br />         (setvar "osmode" 0)<br />         (setq $$mptReactor (vlr-lisp-reactor data '((:vlr-lispEnded . recover_snap))))<br />         (setq pt (list mx my mz))<br /> )

zqw_zhang

2楼的大哥，你的是不是R14不能用呀？？

doubao

可能吧。R14的Autolisp可能不支持反应器（Reactor）

yshf

2. ;也可以这样：
   
3. (defun zhd(pt1 pt2)
   
4.    (mapcar '* '(0.5 0.5 0.5) (mapcar '+ pt1 pt2))
   
5. )

;也可以这样：<br /> (defun zhd(pt1 pt2)<br />    (mapcar '* '(0.5 0.5 0.5) (mapcar '+ pt1 pt2))<br /> )

firstintimate

都可以

2. (defun getmidpoint(pt1 pt2)
   
3.    (mapcar  '(lambda (x y)(/(+ x y) 2))pt1  pt2)   
   
4. )

(defun getmidpoint(pt1 pt2)<br />    (mapcar  '(lambda (x y)(/(+ x y) 2))pt1  pt2)    <br /> )

yshf

点(1 1)和点(2 2)的中点为(1.5 1.5)， eachy和firstintimate的函数皆得不到正确的结果，
Command: (setq pt (xd-mid_point '(1 1) '(2 2)))
(1 1)
Command: (rtos (car pt) 2 10)
"1"
Command: (setq pt (getmidpoint '(1 1) '(2 2)))
(1 1)
Command: (rtos (car pt) 2 10)
"1"

应分别修改为如下：

2. (defun xd-mid_point (p1 p2)
   
3.   (mapcar '(lambda (x) (/ x 2.0)) (mapcar '+ p1 p2))
   
4. )

(defun xd-mid_point (p1 p2)<br />   (mapcar '(lambda (x) (/ x 2.0)) (mapcar '+ p1 p2))<br /> )

2. (defun getmidpoint(pt1 pt2)
   
3.    (mapcar  '(lambda (x y)(/(+ x y) 2.0)) pt1  pt2)   
   
4. )

(defun getmidpoint(pt1 pt2)<br />    (mapcar  '(lambda (x y)(/(+ x y) 2.0)) pt1  pt2)    <br /> )

eachy

这是 Autolisp 运算规则，两数运算均为整数时结果为整数，有一个实数时结果为实数
_$ (/ 3 2)
1
_$ (/ 3 2.)
1.5
_$ (/ 3. 2)
1.5

firstintimate

呵呵，是啊，这就是弱类型语言的问题

xyz518mm

如果是串列表座标该怎样用这函数处理呢?
如表为 ((718.412 755.629) (1520.57 863.88) (906.125 266.541))

hhc_1

我一般这样求中点:

2. 
   
3. (defun getmidpoint(pt1 pt2)
   
4.   (polar pt1 (angle pt1 pt2) (* (distance pt1 pt2) 0.5))
   
5. )

<br /> (defun getmidpoint(pt1 pt2)<br />   (polar pt1 (angle pt1 pt2) (* (distance pt1 pt2) 0.5)) <br /> )

;不知在速度上哪个快些

jx2008

就是速度上的问题了，应该没有多大差别

leeyuan

11楼的程序涉及方向判断的问题，你这种写法不一定求出就是中点