Merge two polylines

Hello guys, I don't know why but i got stacked with my lisp!

I've to create a polyline from a list of points and I really can't understand how to do that. I just searched everywhere but something is missed..

That's what I'm doing:

1. create a polyline -> extract coordinates

(SETQ coordinate1 (VLAX-SAFEARRAY->LIST
                    (VLAX-VARIANT-VALUE (VLAX-GET-PROPERTY obj1 'Coordinates))
                  )
 )

2. doing an offset from it and extract coordinates

(SETQ coordinate3 (VLAX-SAFEARRAY->LIST
                    (VLAX-VARIANT-VALUE (VLAX-GET-PROPERTY obj1 'Coordinates))
                  )
 )

Now I want to merge these lines (merge list of points and entmake a polyline).

The second one is oriented as the first one, I need to invert it!

I have 2 problems:

1. can't append the list of points, because i got something like that:

(1 2 3 4 5 6 ..) instead of ((1 2) (3 4) (5 6) (..) ..)

(setq lista_punti (append lista_punti (list (nth n coordinate1) (nth (1+ n) coordinate1))))

2. Really don't know exactly of to entmake that.. I saw something with lamda funcion.

(entmakex
       (append
  (list
    '(0 . "LWPOLYLINE")		;nome
    '(100 . "AcDbEntity")
    '(100 . "AcDbPolyline")
    ;'(8 . "Muri")		;layer
    ;'(62 . 5)			;colore
    (cons 90 (length coordinate1))			;numero vertici
    '(90 . 4)
    '(70 . 1)			;1 chiusa, 0 aperta
    )
 ;istructions here?
 )
 )

Can someone give me an advice please?

Thanks

A guy named freerefill put this together a while back. Not the cleanest code ever, but it's super reliable.

  (defun plverts (ent / retn listy retDum add1 add2) ;
   (vl-load-com)
   (if	(= (cdr (assoc 0 (entget ent))) "LWPOLYLINE")
     (progn
(setq retn  nil
      listy (vlax-safearray->list
	      (vlax-variant-value
		(vla-get-coordinates (vlax-ename->vla-object ent))
	      )
	    )
)
(while (and (setq var1 (car listy)) (setq var2 (cadr listy)))
  (setq retn (append retn (list (list var1 var2 0))))
  (setq listy (cddr listy))
)
     )
   )
   retn
 )					; Returns a list of 3D coordinates defining the vertices of a polygon

So you can do this:

(SETQ coordinate1 (plverts ent1))

to get your points for both, then just append the two lists.

I guess that I don't understand.

Do you want a continuous pline to incorporate the 2 exiting lines with vertices thru the mid points of the shape and add end caps as well ?

The vertex order shown in attached jpg would not have any overlaying segment

-David

This is another example create a pline form a list of points.

; co-ordsxy is a list of 2d points
(setq x -1) ; so x starts at nth 0 at start and closing
(command "PLINE" (while (= (getvar "cmdactive") 1)
                   (COMMAND (repeat (length co-ordsxy) 
                            (nth (setq x (+ x 1)) co-ordsxy)
                            )
                    )
                 )   
)
(command "C")