List.FilterByBoolMask indexing problem

[PerfectArchCo]

As a way to understand what CODE A is doing I’ve tried to break it apart and replicate it in CODE B.

20 surfaces go in, removing any below the Z axis, leaving 10. However, my CODE B continues to pass through all 20 surfaces. “[1]” in the original code seems to be key to the issue but after trying many configurations I can’t replicate the output of CODE A. I’ve read, in researching the problem, the square brackets are addressing which item to process or pass through etc. but I can’t fathom where to put it.

Any hints would be appricated.

Thanks,

[Vikram_Subbaiah]

From the limited available information, I’d suggest the following…
et2 = List.FilterByBoolMask(surf1,et,Z<0)[“out”];
Flatten(et2);

[PerfectArchCo]

hehe. Thanks for the quick reply. It worked! But I’m not sure why.

[Vikram_Subbaiah]

Hope this helps explain …