number_parser.rb

# number_parser.rb - Josh Sandlin - 2:03PM 3/28/2010
# translating some Java ideas over to Ruby code.

require 'test/unit'

class Node

  def evaluate; end

end

class ValueNode < Node

  attr_accessor :value

  def initialize( value )
    @value = value
  end

  def evaluate
    @value
  end
  
end

class OpNode < Node

  attr_accessor :left, :right

  def initialize
    @left = Node.new
    @right = Node.new
  end

  def evaluate; end

end

class AdditionNode < OpNode
  
  def initialize( left, right )
    @left, @right = left, right
  end

  def evaluate
    left.evaluate + right.evaluate
  end

end

class MultiplicationNode < OpNode

  def initialize( left, right )
    @left, @right = left, right
  end

  def evaluate
    left.evaluate * right.evaluate
  end

end

# unit tests

class ExpressionTreeTest < Test::Unit::TestCase

  def test_addition
    assert_equal 5, AdditionNode.new( ValueNode.new( 3 ),
                                      ValueNode.new( 2 ) ).evaluate
    assert_equal 4, AdditionNode.new( ValueNode.new( 2 ), 
                                      ValueNode.new( 2 ) ).evaluate
    assert_equal 1, AdditionNode.new( ValueNode.new( 1 ),
                                      ValueNode.new( 0 ) ).evaluate              
  end

  def test_multiplication
    assert_equal 6, MultiplicationNode.new( ValueNode.new( 2 ),
                                            ValueNode.new( 3 ) ).evaluate
    assert_equal 2, MultiplicationNode.new( ValueNode.new( 2 ),
                                            ValueNode.new( 1 ) ).evaluate
    assert_equal 9, MultiplicationNode.new( ValueNode.new( 3 ),
                                            ValueNode.new( 3 ) ).evaluate
  end

  def test_mixed_operations
    assert_equal 7, AdditionNode.new( ValueNode.new( 1 ),
                                      MultiplicationNode.new( ValueNode.new( 2 ),
                                                              ValueNode.new( 3 ) ) ).evaluate
  end

end