Item previous to an index in a list

Hi everybody,

I’m currently trying to get the thickness of all the upper layer of a slab.
I’ve managed a way to do that but I’ve a problem if the slab is only composed of a structural layer …
It returned the value of the structural layer instead of 0 as you can see here :

I’m also trying to get rid of the last null value in yellow, the “List.Clean” node doesn’t work as I would like …

Thanks !

slablayer.dyn (14.8 KB)

You can use Object.IsNull with Bool Mask to filter the list you want.

Thanks it’s working !

Just need to solve my problem with the structural slab now :slight_smile: