Re: 5.2 work3 manual

[Roberto Ierusalimschy <roberto@...>]

> > What do you mean by "the array part of a table"?
> 
> That a table x (if constructed) would be the array part of a table t if:
> 
>   define n to be the greatest integer for which t has keys
>   1,2, ... ,n or zero if t has no such keys;
>   then x has keys 1,2, ... ,n and x[i] == t[i] has the value true for
>   i = 1,2, ... ,n or else x is {}.
> 
> What I mean by "has keys" troubles me in the light of the fact
> that if x = { } and y = { nil } then x[1] == y[1] is true.
> Yet x has no keys, whereas y has 1 as a key. So there appears to
> be no way semantic way of testing "having the same keys" -
> one is appealing to what is happening "under the hood".

In Lua, the only sensible definition for "t has no key y" is "t[y] is
nil"; otherwise all tables have all keys. In your example, 'y' has no
keys (exactly as 'x').

-- Roberto