# -*- ruby -*-

class Point
  attr_accessor :x

  def translate(x)
    p = clone
    p.x += x
    p
  end

  def add(p)
    if type == p.type
      real_add(p)
    else
      fail "#{type}.add only works with #{type}'s"
    end
  end
end


class Point2d < Point
  attr_accessor :y

  def initialize(x, y)
    @x, @y = x, y
  end

  def real_add(p)
    Point2d.new(@x + p.x, @y + p.y)
  end

  def length()
    Math.sqrt(@x * @x + @y * @y)
  end

  def to_s()
      "[%g, %g]" % [@x, @y]
  end
end

class Point3d < Point
  attr_accessor :y, :z

  def initialize(x, y, z)
    @x, @y, @z = x, y, z
  end

  def real_add(p)
    Point3d.new(@x + p.x, @y + p.y, @z + p.z)
  end

  def length()
    Math.sqrt(@x * @x + @y * @y + @z * @z)
  end

  def to_s()
      "[%g, %g, %g]" % [@x, @y, @z]
  end
end

p2d = Point2d.new(3, 4)
p3d = Point3d.new(1, 2, 2)

l = [ p2d, p3d ]

def test(p)
  return p.length, p.translate(1)
end

print [ test(p2d), test(p3d), l.map{|p| p.length} ].join(" "), "\n"

# after translate, we still have a Point3d
print p3d.translate(1).z, "\n"

def twice(p)
  p.add(p)
end

print [ twice(p2d), twice(p3d), l.map{|p| twice(p)} ].join(" "), "\n"
#print p2d.add(p3d)
#print p3d.add(p2d)

# after twice, we still have a Point3d
print twice(p3d).z, "\n"