Re: Is this Lua table an array?

[Nick Gammon <nick@...>]

On 03/10/2006, at 7:42 PM, Ashu Sharma wrote:

> I am just wondering if there's a good way of finding whether a  
> given Lua
> table is actually an array.

> One way is to iterate over the table using 'pairs' and see if any  
> of the
> keys is a non-number.


You would have to define "an array" here.

Is this an array?

t = {}  --> no non-numbers

What about this?

t = { "a","b", [4] = "c" }  --> has gaps

Or this?

t = { "a","b", [100000] = "c" }  --> has a big gap

How about:

t = { [0] = "a" }  --> no gaps, but won't be picked up by ipairs


I am inclined to think that you make your own definition of what an  
array is, and write a function to detect if a particular table meets  
that condition.

One way would be to traverse the table using ipairs, and again using  
pairs, and see if the number of elements is the same in both cases.  
Obviously that could be slow.

- Nick