Re: Question about arrays...

[Andrew Starks <andrew.starks@...>]

On Sunday, June 9, 2013, Dirk Laurie  wrote:
> 2013/6/9 Tim Hill <drtimhill@gmail.com>:
>
> > As the Lua docs state, an array is a table with a sequence
> > of elements from 1..N.
> >
> > But my question is: is it ok to build the array out of order?
> > For example:
> >
> > a = { 1, [3]=3 }
> > a[2]=2
> >
> > Is "a" an array?
>
> The actual term is "sequence" but I know what you mean. Yes, it is.
>
> > Lua *seems* to think it is (#a returns 3), but the Lua docs seems
> > to be a bit vague on this (it seems to be implied by the term
> > "sequence" in the ref manual).
>
> Not vague, but not labouring the point either. Let's say the Manual
> is mathematically precise on the subject.
>
>     We use the term sequence to denote a table where the set of all
>     positive numeric keys is equal to {1..n} for some integer n,
>     which is called the length of the sequence.
>
> Actually, the routines that depend on this property are not confused
> by positive numeric keys that can't be taken for integers, but the
> above is what it says.

I've been confused on a related matter:

I know that in the current implementation, a sequence  that also contains hashes will still work as a sequence. That is, in my experience:

T = {"at one", "at two", property = "some value"}

...works in ipairs and with the length operator. Is this behavior that is dependent on the implementation or is it something that is a formal part of Lua?

-Andrew