Re: Why is nil not a valid table key?

[Chris Marrin <chris@...>]

Rici Lake wrote:
> On 26-Nov-05, at 10:29 AM, Mike Pall wrote:
>
> > Lua signals the end of a table traversal with a nil key. This is
> > both simple and efficient.

It is pretty easy to store a 'length' property in a table to identify 
how many numeric keys it has. I found that technique ALMOST works in 
Lua. If a table has entries for numeric keys 1,2,12 and 17, and I set 
the length property to 17 then I can go:

    for i=1,t.length do
        print(t[i])
    end

and I will get all the numbers printing out, with nils in the slots that 
don't have a numeric index.

But I found that attempting to set:

    t[0] = "hello"

does not work. When I read this back, it prints nil. Is this true, or do 
I have a bug in my logic somewhere? I thought Lua only cared about 
"arrays starting at 1" when you fill a table like this:

    local t = { 12,17,627 }

In which case t[1] == 12. But can you not even set a numeric property on 
a table with the numeric key of 0? If so, that seems very broken...

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