trying to understand binary trees using Ruby. had this on my desktop, wanted it off, but didn't want to lose it

gistfile1.rb

class BinaryTree
  def initialize
    @size = 0
    @root = nil
  end
  
  def insert(data)
    node = BinaryTreeNode.new(data)
    
    if @root.nil?
      @root = node
    else
      @root.insert(node)
    end
  end
  
  def in_order
    @root.in_order
  end
  
  def pre_order
    @root.pre_order
  end
  
  def post_order
    @root.post_order
  end
end

class BinaryTreeNode
  include Comparable
  
  attr_reader :data
  
  def <=>(another)
    self.data <=> another.data
  end
  
  def initialize(data)
    @data = data
    @left = nil
    @right = nil
  end
  
  def insert(node)
    position = self <=> node
    case position
    when 1
      if(@left.nil?)
        @left = node
      else
        @left.insert(node)
      end
    when -1
      if(@right.nil?)
        @right = node
      else
        @right.insert(node)
      end
    else
      raise "something bad happened"
    end
  end
  
  def in_order
    @left.in_order if @left
    puts self.data
    @right.in_order if @right
  end
  
  def pre_order
    puts self.data
    @left.pre_order if @left
    @right.pre_order if @right
  end
  
  def post_order
    @left.pre_order if @left
    @right.pre_order if @right
    puts self.data
  end
end

tree = BinaryTree.new
tree.insert(5)
tree.insert(3)
tree.insert(8)
tree.insert(1)
tree.insert(4)
tree.in_order
puts
tree.pre_order
puts
tree.post_order

class BinarySearchTree < BinaryTree
  def insert(data)
    node = AVLNode.new(data)
    
    if(@root.nil?)
      @root = node
    else
      @root.insert(node)
    end
  end
end

class AVLNode
  def initialize(data)
    @data = data
    @left = nil
    @right = nil
    @factor = 0
  end
end