Re: How many elements in this table?

[Rici Lake <lua@...>]

On 20-Mar-05, at 5:25 PM, Eric Tetz wrote:
> How can I tell the number of elements in table T? I'm not using it as
> a list, so table.getn always returns 0. Do I need to write something
> like this?
>
> function numelements (t)
>   local n = 0
>   for k,v in t do
>     n = n + 1
>   end
>   return n
> end

Exactly.

> That seems very kludgey.

Perhaps. But why would you want to know?

The closest I usually come to this question is asking whether a table 
is empty, or sometimes if it has more than one key/value pair. The 
following are useful:

function is_empty(t) return next(t) == nil end

function is_multiple(t)
  local first = next(t)
  return next(t, first) ~= nil
end

and for what its worth

function has_at_least(t, n)
  local k = nil
  for i = 1, n do
    k = next(t, k)
    if k == nil then return false end
  end
  return true
end