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 (2025-07-10 15:41:47 GIT hash eafa42ae743de61b62f958948d7abb5fada7756f 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.