Lisp Help - Looping through a list

[kymba]

Hi All

 

first post as google & forum searches usually net what i'm chasing, but this is beyond me.

 

I have some code (previously posted by ASMI here) that returns the coordinates of each vertex in a polyline.

 

I now want to loop through this list and check for an an intersection between each segment of a polyline and 2 other points

 

what i have so far gets me the two endpoints, but from here i haven't a clue

 

(defun c:asdf (/ whoa pts ep1 ep2)
 (setq whoa (mapcar 'cdr(vl-remove-if '(lambda(x)(/= 10(car x)))(entget(car(entsel))))))
(setq pts (cdr whoa))
(setq ep1 (car pts))
(setq ep2 (cadr pts))
 (princ)
)

[CarlB]

I'd suggest you use the 'nth' function to retrieve needed points from list. Get length of list with 'length' function. Set up a counter; first time through use pt1 & pt2; then pt2 & pt3; up through last point.

[kymba]

Thanks CarlB

 

you gave me an idea to use a 'while' in there with the length check

 

(defun c:asdf (/ whoa pts ep1 ep2)
 (setq pts (mapcar 'cdr(vl-remove-if '(lambda(x)(/= 10(car x)))(entget(car(entsel))))))
(while (>= (length pts) 2)
(setq ep1 (car pts))
(setq ep2 (cadr pts))
 	(setq pts (cdr pts))
(princ)
)
)

 

does this seem ok? i've never looped before

 

i also realised that my first lot of code stripped off the first vertex...oops