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- Subject: Is this NEXT behavior expected or lucky coincidence?
- From: <tonyp@...>
- Date: Tue, 14 Apr 2015 22:54:35 +0300
I have been using the following iterator for some time but it just occurred
to me that it may work by lucky accident.
I have tested it with Lua v5.1, v5.2, and v5.3 and it always gives correct
results for any table that contains any combination of key-value pairs
and/or lists (indexed 1..n) provided there are no gaps in the 1..n numeric
local key = #t
if key == 0 then key = nil end
"for k,v in kpairs(t) do print(k,v) end" will iterate over and print all
non-list (1..n) elements of the given table. (Again, assuming there are no
gaps in the sequence.)
But this behavior does not seem to be guaranteed by the 'next' documentation
(unless I missed something) which says: "The order in which the indices are
enumerated is not specified, even for numeric indices."
(BTW: In LuaJIT, it fails just for index 0 -- and possibly other cases I
didn't test as I rarely use LuaJIT)
So, my question is:
Can I rely on this behavior for standard Lua, or is this an implementation
accident that could stop working any time a new version comes out?
(Or, is it even the case that even the current implementation won't work for
all cases, and I simply was lucky enough not to hit those? Examples where
it wouldn't work?)