RE: not understanding return statement

In your method #insert, root is just a variable.  Putting   `root` as the last statement in #insert will return the value of that variable from the #insert method.

But it won’t set the @root attribute on the class, which is what you are reading when you say `p x.root`.  @root is an attribute on the class BinarySearchTree; root is a variable in the insert method. They are not the same thing.

I suspect you need to go back and learn some more about classes and attributes – sorry.

From: ruby-talk [mailto:[email protected]] On Behalf Of Igor Maljkovic
Sent: 12 December 2018 10:08
To: [email protected]
Subject: not understanding return statement

Hi all, I need help understanding part of my code. I'm learning about data structures, at the moment binary search tree.
This code does what I want, but I don't understand return statement in insert
method. Why @root = root works as it works. If i put last line just root,
global variable root is nil instead of tree filled with nodes.
Here is my code:
class BinarySearchTree

  class Node
    attr_accessor :value, :left_child, :right_child
    def initialize(value)
      @value = value
      @left_child = nil
      @right_child = nil
    end
  end

  attr_accessor :root
  def initialize()
    @root = nil
  end

  def insert(root = @root, value)
    if root == nil
      root = Node.new(value)
    elsif value <= root.value
      root.left_child = insert(root.left_child, value)
    else
      root.right_child = insert(root.right_child, value)
    end
    @root = root #works with this return statement
    #root <- doesn't work with this statement, why!!!
  end
end

x = BinarySearchTree.new()
x.insert(15)
x.insert(10)
p x.root


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