Re: not understanding return statement

@root is the same as BinarySearchTree.root
In your insert method you are not returning something but assigning the
instance of your BinarySearchTree.root the value of the internal variable
root.

If you want to use a return statement you can just use ‘root’ at the end
but you have to change the line where you call the insert method.

x.root = x.insert(15)

I don’t recommend this but I hope you understand a little better what is
happening in your code.

PS: Read about classes, instances and attributes. Especially  attributes.

On Wed, Dec 12, 2018 at 13:33 Ale Miralles <[email protected]> wrote:

> If you want to see a working implementation of binary search trees in
> Ruby, you may want to take a look at this:
>
> https://medium.com/amiralles/mastering-data-structures-in-ruby-avl-trees-6206bf2035e0
>
> Also, for other data structures:
> https://medium.com/amiralles
>
> Take a look at those posts first, and let me know if you need some help.
>
> ~ Ale Miralles.
>
>
> On Wed, 12 Dec 2018 at 08:16, Andy Jones <[email protected]>
> wrote:
>
>> 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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