text: # -*- coding: utf-8 -*-
  
  from guietta import E, _, Gui, Quit
  
  gui = Gui(
      
    [  'Enter expression:', E('expr')  , _ ],
    [  'Result:'          , 'result'    , _          ],
    [  _                  , _           , Quit       ] )
  
  
  gui.events(
      
      [  _            ,   ('textEdited', None) , _    ], 
      [  _            ,   _                       , _    ], 
      [  _            ,   _                       , _    ], )
  
  
  while True:
      name, event = gui.get()
  
      if name == 'expr':
          try:
              gui.result = eval(gui.expr)
          except Exception as e:
              gui.result = 'Error: ' + str(e)
  
      elif name == None:
          break
      