Number of elements in an array

How i can know how many elements of certain type are in an array? For example my_array = ['cat', 'dog', 'cat'] and i want to know that there are: 2 'cat' and 1 'dog'

to search for a specific element and count it you can use:

List.count = function(element)
  // return the times 'element' appears in List
  local c = 0
  for i in this
    if i == element then c += 1 end
  end
  return c
end

and the call my_array.count('cat') returns 2

to search for all elements in the list and count them:

List.countAll = function()
  // return an object with the elements of List and their count
  local c = object end
  for i in this
    c[i] += 1
  end
  return c
end

my_array.countAll() returns:

object
  cat = 2
  dog = 1
end

note that you can compere only numbers and strings

Thanks