parralel lines

hi,

to check if two lines are parallel, i have been using
(if (not (inters a b c d nil))
where a and b are the endpoints of line 1
and c d the endpoints of line 2

what would be the fastest way to check
if they are parallel to a 1 degree tolerance?

TIA

 

Try this:

(defun c:cll (/ l1 l2)
(setq l1 (ssget "+.:E:S" (list (cons 0 "LINE")))
l2 (ssget "+.:E:S" (list (cons 0 "LINE")))
)
(areparallel (ssname l1 0) (ssname l2 0) 1.0)
)

(defun areparallel (l1 l2 fuzz / o1 o2 a1 a2 )
(vl-load-com)
(setq
o1 (vlax-EName->vla-Object L1)
o2 (vlax-EName->vla-Object L2)
a1 (rem (rtd (vla-get-angle o1)) 180)
a2 (rem (rtd (vla-get-angle o2)) 180)
)
(<= (abs (- a2 a1)) fuzz)

)

(defun RTD (a) ;Radians to degrees conversion
(* 180.0 (/ a pi)))

 

Slight correction, in case the angles calculate out to 180 and 0:

(defun areparallel (l1 l2 fuzz / o1 o2 a1 a2 )
(vl-load-com)
(setq
o1 (vlax-EName->vla-Object L1)
o2 (vlax-EName->vla-Object L2)
a1 (rem (rtd (vla-get-angle o1)) 180)
a2 (rem (rtd (vla-get-angle o2)) 180)
)
(or (equal a2 a1 fuzz)
(equal (abs (- a2 a1)) 180 fuzz)
)
)

 

thanks