old_contents: # -*- coding: utf-8 -*-
  #
  from .line_loop import LineLoop
  
  
  class RuledSurface(object):
      _ID = 0
  
      def __init__(self, line_loop):
          assert isinstance(line_loop, LineLoop)
  
          self.line_loop = line_loop
  
          self.id = 'rs{}'.format(RuledSurface._ID)
          RuledSurface._ID += 1
  
          self.code = '\n'.join([
              '{} = news;'.format(self.id),
              'Ruled Surface({}) = {{{}}};'.format(self.id, self.line_loop.id)
              ])
          return
  
new_contents: # -*- coding: utf-8 -*-
  #
  from .line_loop import LineLoop
  
  
  class RuledSurface(object):
      _ID = 0
      num_edges = 0
  
      def __init__(self, line_loop):
          assert isinstance(line_loop, LineLoop)
  
          self.line_loop = line_loop
  
          self.id = 'rs{}'.format(RuledSurface._ID)
          RuledSurface._ID += 1
  
          self.code = '\n'.join([
              '{} = news;'.format(self.id),
              'Ruled Surface({}) = {{{}}};'.format(self.id, self.line_loop.id)
              ])
          self.num_edges = len(line_loop)
          return
  
subject: add RuledSurface.num_edges