Fraction Assignment

Your assignment: Complete the Fraction class (with unit tests).

• Provide methods to add, subtract, multiply, divide, and invert fractions
  • Example: new_fraction = fraction_1.multiply fraction_2
• All fractions should be stored in a normalized form
  • If the fraction is negative, only the numerator should be negative
  • If the fraction is positive, the numerator and denominator should both be positive
  • If the fraction is zero, it should be stored as 0/1
  • Zero is never a legal denominator
• Provide complete unit tests for all (nonprivate) methods

Starter code follows...

fraction.rb

class Fraction

  attr_reader :numerator, :denominator
  
  def initialize numerator, denominator
     throw Exception.new("Illegal zero denominator") if denominator == 0
    @numerator = numerator
    @denominator = denominator
    reduce
  end
  
  def to_s
    @numerator.to_s + '/' + @denominator.to_s
  end
  
  def == other # Yes, I'm redefining ==
    @numerator == other.numerator and @denominator == other.denominator
    true
  end
  
  private
  def reduce
    n, d = @numerator, @denominator
    while n != d
      if n > d
        n -= d
      else
        d -= n
      end
    end
    @numerator /= n
    @denominator /= n
  end
  
end

test_fraction.rb

require 'Fraction'

class TestFraction < Test::Unit::TestCase
  @@f_3_4 = Fraction.new(3, 4)
  
  def setup
    # Stuff to be done before each test method
  end
  
  def teardown
    # Stuff to be done after each test method
  end
  
  def test_new
    assert_equal(@@f_3_4, Fraction.new(3, 4))
    assert_equal(@@f_3_4, Fraction.new(30, 40))
    # Negative numbers may cause an infinite loop
    # assert_equal(@@f_3_4, Fraction.new(-3, -4))
  end
  
end