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

Note: as @eric points out, pairs is not defined to iterate in a specific order. Hence this is no valid answer.

The following should be sufficient; it checks that the keys are sequential from 1 until the end:

local function isArray(array)
  local n = 1
  for k, _ in pairs(array) do
    if k ~= n then return false end
    n = n + 1
  end

  return true
end