How can I check if a lua table contains only sequential numeric indices?

Question

How can I write a function that determines whether it\'s table argument is a true array?

isArray({1, 2, 4, 8, 16}) -> true
isArray({1, \"two\", 3, 4, 5}) ->         


        

Answer 1

Here's my take on this, using #array to detect a gap or stop when too many keys have been read:

function isArray(array)
  local count=0
  for k,_ in pairs(array) do
    count=count+1
    if (type(k) ~= "number" or k < 1 or k > #array or count > #array or math.floor(k) ~= k) then 
      return false
    end
  end
  if count ~= #array then
    return false
  end
  return true
end