maybe the sparse function that ¦ relies on uses vectorization instead of an explicit map, but at the same time ¦ doesn't vectorize? I think that could explain the issue

ret = iterable(variadic_link(link, args)) does look like it's doing that

Okay wow yeah I put a € after the ¦ and it worked fine

now to do the actual challenge

I thought that this five-line, nilad-filled abomination worked for all cases where the given indices don't correspond to an element on the edge...

I was wrong

well, index, because it's one index, just a multidimensional one

but yeah I thought I had it and I didn't and I don't quite get why

@lolad hm, do you have a GH account?