The polyline closed or not

How to identify the selected polyline is closed or not by LISP

One way, via the group code 70

There is THIS too.

Here is one way to only select closed polylines

(ssget '((0 . "POLYLINE,LWPOLYLINE")(-4 . "&")(70 . 1)))

Lisp to select a lwpolyline and see if it's closed:

(vlax-curve-isClosed (car(entsel)))

You could also use the function to test preselected entities as well.

Thanks everybody for your codes and quick replies.

Here is one way to only select closed polylines

 

(ssget '((0 . "POLYLINE,LWPOLYLINE")(-4 . "&")(70 . 1)))

FWIW, you also need to check for:

(ssget '((0 . "lwpolyline") (-4 . "<OR") (70 . 1) [b](70 . 129)[/b] (-4 . "OR>")))

When PLINEGEN is set to 1.

@ronjonp - did you try it?

The [&] is a Bitwise AND operator. To determine if the polyline is closed, you are looking for the presence of the "1" bit in the dxf70 code, not just the two values "1" and "129".

So the code I posted works on both heavy and lightweight polylines, regardless of the setting of PLINEGEN, whether or not it is a 3D polyline, spline fit, curve fit, etc.

Your code will only select lightweight closed polylines. It ignores closed heavy polylines, closed 3D polylines, closed spline fit/curve fit polylines, etc.

@ronjonp - did you try it?

 

The [&] is a Bitwise AND operator. To determine if the polyline is closed, you are looking for the presence of the "1" bit in the dxf70 code, not just the two values "1" and "129".

 

So the code I posted works on both heavy and lightweight polylines, regardless of the setting of PLINEGEN, whether or not it is a 3D polyline, spline fit, curve fit, etc.

 

Your code will only select lightweight closed polylines. It ignores closed heavy polylines, closed 3D polylines, closed spline fit/curve fit polylines, etc.

Thanks for the reply I did not know that!

For what it's worth, when matching a single bit-code (such as 1=Closed), I would be inclined to use the bitwise masked equals operator ("&=") which behaves the same as (= (logand )); though this is just syntactic sugar, as both bitwise operators will perform equally well in this case.

This post may help to explain the difference between the two bitwise operators ("&" and "&="), I also provide some examples in my reference here.

thanks Lee Mac!

You're most welcome RK!