John Belmonte wrote:
Programming in Lua refers to nil in a list as a "hole", but that is
from the perspective of Lua's table representation which cannot
distinguish nil-valued from nonexistent keys. From the view of the
list creator, why should either of the following be considered as
having holes?
I think part of the problem comes from the fact that some people
distinguish nil-valued from non-existent keys. But the concept of a
non-existent key is not applicable to Lua tables. In Lua a table
is an
infinite associative array, with all possible keys having a value. By
default all keys have a nil value. These nils are not explicitly
stored,
but that's an implementation detail.
In that context the # operator is not well defined. I see two good
(though not perfect) solutions: either make the table # operator
deterministic (for example return the biggest integer key), or allow
users to override the # operator (that's my prefered solution,
since it
would be useful for other problems, like returning the norm of a
vector).
