has element at index `i` been set already? This is true after an explicit call to `put i v` for some value `v` or for indices in the range `0..length-1` for all indices that existed before `expand` was called.
0.094dev (2025-06-18 15:08:51 GIT hash 89cffc23ae669b0898a5564fefbf793fcb8e5ca7 built by fridi@fzen)
call to `put i v` for some value `v` or for indices in the range `0..length-1`
for all indices that existed before `expand` was called.