reduce

# File lib/rational.rb, line 71
  def Rational.reduce(num, den = 1)
    raise ZeroDivisionError, "denominator is zero" if den == 0

    if den < 0
      num = -num
      den = -den
    end
    gcd = num.gcd(den)
    num = num.div(gcd)
    den = den.div(gcd)
    if den == 1 && defined?(Unify)
      num
    else
      new!(num, den)
    end
  end