def __init__(self, grammar, sent, trace=0):
self._sent = sent
self._parser = SteppingShiftReduceParser(grammar, trace)
# Set up the main window.
self._top = Tk()
self._top.title('Shift Reduce Parser Application')
# Animations. animating_lock is a lock to prevent the demo
# from performing new operations while it's animating.
self._animating_lock = 0
self._animate = IntVar(self._top)
self._animate.set(10) # = medium
# The user can hide the grammar.
self._show_grammar = IntVar(self._top)
self._show_grammar.set(1)
# Initialize fonts.
self._init_fonts(self._top)
# Set up key bindings.
self._init_bindings()
# Create the basic frames.
self._init_menubar(self._top)
self._init_buttons(self._top)
self._init_feedback(self._top)
self._init_grammar(self._top)
self._init_canvas(self._top)
# A popup menu for reducing.
self._reduce_menu = Menu(self._canvas, tearoff=0)
# Reset the demo, and set the feedback frame to empty.
self.reset()
self._lastoper1['text'] = ''
