Join arc and line using AutoLISP

I'm trying to join an arc and a line. I've tried the following:

(setq arc1 (entmakex-arc cen rad ang1 ang2 lyr))
(setq pt1 (vlax-curve-getStartPoint arc1))
(setq pt2 (vlax-curve-getEndPoint arc1))
(setq lin1 (entmakex-line pt1 pt2 lyr))
(vl-cmdf "._join" arc1 lin1)

'entmakex-arc' and 'entmakex-line' are functions to make the respective entities (params should be self-explanatory). This code draws the arc and the line properly but will not perform the join. I've searched the internet for an hour now, and cannot find anything that works. What is wrong with this code? Or, if there's a better way to approach this task, please tell. I've tried variations adding an empty string "" to the end of the vl-cmdf parameters, but nothing works.

Note that the entities are drawn in AutoCAD and I can manually join them together, so the endpoints match up, etc. But, I need to automate the join part. Any help is appreciated.

Some food ...

http://www.cadtutor.net/forum/showthread.php?84221-Lisp-to-Select-Picking-line-arc-spline-to-Create-Polyline&p=576903&viewfull=1#post576903

Another.

(vl-cmdf "._pedit" lin1 (if (eq (getvar 'peditaccept) 0) "_Y") "" )
(vl-cmdf "._join" (entlast) arc1 "")

or

(vl-cmdf "._pedit" lin1 (if (eq (getvar 'peditaccept) 0) "_Y") "_J" arc1 "" "")

If it is always a single arc with the endpoints connected, why not just (entmake) the LWPOLYINE ? -David

Yes, it's always a single arc with line connecting the endpoints. This sounds like a great idea, and almost certainly more efficient than the way I'm approaching it now. I've only done really basic stuff with entmake and entmakex. Could you provide a few lines of example code for this? Thanks.

@Tharwat and GP_

I've used a combination of your posts, and almost have a working function. It's joining the first arc/line combo, but still crapping out on me after that. I need to review other parts of the code and sort of clean house to find the issue. Probably tomorrow. Thanks for the input.

If it is always a single arc with the endpoints connected, why not just (entmake) the LWPOLYINE ? -David

I was looking around for some example code for creating a polyline and found:

1. http://www.theswamp.org/index.php?topic=9728.0
   
2. http://forums.autodesk.com/t5/Visual-LISP-AutoLISP-and-General/lwpolyline-with-entmake/td-p/2421606
   

These use a list of points to create the polyline, which is feasible, but is there any way to do it using an arc? I know I could approximate the arc by picking off a few points from the arc, but is there an exact way?

If it is always a single arc with the endpoints connected, why not just (entmake) the LWPOLYINE ? -David

I ended up going to with this option and it worked. It was close enough to what I needed, and worked first time (with code from http://www.theswamp.org/index.php?topic=9728.0). Thanks for the idea.

Glad you got it to work. I was trying to come up with absolute minimum code to use with entmake. -David