local Node = {}
Node.__index = Node

function Node.new(data)
	local node = setmetatable({}, Node)
	node.data = data
	node.left = nil
	node.right = nil
	return node
end

-- return an iterator that traverses the tree in order
function Node:inorder()
	local stack = {}
	local current = {self, ""}
	table.insert(stack, current)

	return function()
		while current[1].left do
			local parent = current
			current = {parent[1].left, parent[2] .. "0"}
			table.insert(stack, current)
		end

		if #stack > 0 then
			local node = table.remove(stack)

			if node[1].right then
				local parent = node
				current = {parent[1].right, parent[2] .. "1"}
				table.insert(stack, current)
			end
			return node[1], node[2]
		end
	end
end

return Node