Is there a way to analyze whether a curve is closed or not and convert the yes / no to a Boolean?

Hi,

You can get the prim intrinsic "closed":

That's what I needed, thanks very much.

Just for anyone after this:
-plug the curve into a primitive attribute wrangle
-paste animatrix_ expression in VEXpression field
-check geometry spreadsheet primitive tab
-you'll see a 0 or 1 value depending on whether it's open or closed

If you just want to see whether the curve is closed or not, in the geometry spreadsheet you can display intrinsics, no need to create a new attribute.

You can also directly access that intrinsic in group fields. For example, put down a blast node and set the group parm to to delete all closed curves.

Even better, if I wanted to take that 0 or 1 and have it control the "closed" tick box on the add node, how would I go about that?

Is it possible to paste that as a reference?

I'm not sure what you're trying to do with the add node, but you can certainly lookup a prim's "closed" intrinsic value using the prim(...) expression, such as

-electric fence
-curve to set path
-add node to create connecting wires
-if path curve is open I want to untick closed on the add node, if path curve is closed i want to tick closed on the add node