From: Justin To <tekmc@...>
Date: 2008-06-13T02:06:05+09:00
Subject: Re: Trie data structure

class Trie
  attr_reader :value, :children
  def initialize(value=nil)
    @value = value                      # The corresponding value
    @children = []                       # Store hashes inside of the 
hash
  end

  def <<(value)
    sub_trie = Trie.new(value)
    @children << sub_trie
    return sub_trie
  # End of def <<(value)
  end

  # Return true if value exists or nil if value D.N.E.
  def child_value?(value)
    if @children.empty?              # If @children is empty, then there 
are no children
      return 'empty'
    else
      # If one of the children contains the value then return true
      @children.each do |child|
        if(child.value==value)
          return true
        else
          return nil
        end
      end
    end
  # End of def child_value?(value)
  end

  # Return the child that added the value if the value D.N.E. else 
return nil, the value already exists
  # DO NOT ALTER OR CALL OUTSIDE OF CLASS--belongs to def 
add_number(value)
  def add_digit(digit)
    if(!child_value?(digit))
      child = self<<(digit)
      puts "#{digit} added"
      return child
    else
      puts "#{digit}: already exists in the child."
      return nil
    end
  end

  def add_number(number)
    current_node = self
    number.to_s.each_byte do |byte|
      puts "add_number #{byte.chr.to_i}"
      puts "Nodeclass: " + current_node.class.to_s
      current_node = current_node.add_digit(byte.chr.to_i)
    end

  end

# End of class Trie
end


t = Trie.new
t << 3

t.add_number(234)


Output:

HashTrie3.rb:50:in `add_number': undefined method `add_digit' for 
nil:NilClass (NoMethodError)
  from HashTrie3.rb:47:in `each_byte'
  from HashTrie3.rb:47:in `add_number'
  from HashTrie3.rb:62
add_number 2
Nodeclass: Trie
2 added
add_number 3
Nodeclass: Trie
3: already exists in the child. # ?
add_number 4                    # ?
Nodeclass: NilClass             # ?

Somewhere I'm not saving the current node correctly so when it adds 3, 
it's adding it into the same array that the first 3 (t<<3) and the 2 
[t.add_number(234)] is in. But then again, I could have messed up 
somewhere else. Maybe I'm passing around copies of the current node and 
not the ACTUAL one.

Any help is much appreciated!!!!!!!!!!!!!!!!!!!!

Justin
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