Find vertices 180 degrees or less

My code below inserts blocks on all vertices of a closed pline.

How can I modify it so that blocks are inserted only if the internal angle is 180 degrees or less?

thanks

(setq ent (car (entsel "\nSelect closed polyline: ")))
     e2 (entget e4))
     len (length e2))
     n 0)
);setq
(repeat len
(setq e1 (car (nth n e2)))
(if (= e1 10)
(command "_.INSERT" "myblock" (cdr (nth n e2))  1 "" 0)
);if
(setq n (1+ n))
);repeat

I don't think I quite understand the wording. A closed polyline will be either CW or CCW. In an internal angle, are you referring to the delta of 2 adjacent segments? The XY Plane angle of a given segment? I believe that you will have to extract the point list in order to compare the angles. -David

David yes you are correct thinking about it. I thought I might be able to use the code I had to start with, but I as you say I need a points list to compare xy planes of a given segment.