spiral.rb

  x, y = 0, 0
  xmin, xmax, ymin, ymax = 0, 0, 0, 0
  e = Enumerator.new do |yy|
    loop do
      while x > xmin
        yy << [x, y]
        x -= 1
      end
      xmin -= 1
      while y < ymax
        yy << [x, y]
        y += 1
      end
      ymax += 1
      while x < xmax
        yy << [x, y]
        x += 1
      end
      xmax += 1
      while y > ymin
        yy << [x, y]
        y -= 1
      end
      ymin -= 1
    end
  end
  
  

stripe.rb

  xmin, xmax, ymin, ymax = 1, 5, 1, 5
  dx = 1
  dy = 1
  
  e = Enumerator.new do |yy|
    x = xmin
    y = ymin
    while y <= ymax
      while x <= xmax
        yy << [x, y]
        x += dx
      end
      x = xmin
      y += dy
    end
  end