How can I create a node loop?

Hello there,

I’ve got this situation, where the node ‘‘sastrugi’’ should let me to get a closed curve from a coordinate list

But it doesn’t work to me.
In fact, the node works just if I get a single index by the list whit list.getitematindex, for instance:

However, I should repeat this workflow too much time, so I think I could create a loop for stastrugi node so that this node repeat its command for every index by the list.

How can I create this loop?
otherwise, How can I fix this node?

sastrugi node’s workflow in pic:

Can you repost your images with the node preview bubbles showing so we can actually see the data moving through your graph? Otherwise we’re all just guessing at what’s happening.