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# Natural Language Toolkit: Shift-Reduce Parser Application # # Copyright (C) 2001-2012 NLTK Project # Author: Edward Loper <edloper@gradient.cis.upenn.edu> # URL: <http://www.nltk.org/> # For license information, see LICENSE.TXT
A graphical tool for exploring the shift-reduce parser.
The shift-reduce parser maintains a stack, which records the structure of the portion of the text that has been parsed. The stack is initially empty. Its contents are shown on the left side of the main canvas.
On the right side of the main canvas is the remaining text. This is the portion of the text which has not yet been considered by the parser.
The parser builds up a tree structure for the text using two operations:
- "shift" moves the first token from the remaining text to the top of the stack. In the demo, the top of the stack is its right-hand side. - "reduce" uses a grammar production to combine the rightmost stack elements into a single tree token.
You can control the parser's operation by using the "shift" and "reduce" buttons; or you can use the "step" button to let the parser automatically decide which operation to apply. The parser uses the following rules to decide which operation to apply:
- Only shift if no reductions are available. - If multiple reductions are available, then apply the reduction whose CFG production is listed earliest in the grammar.
The "reduce" button applies the reduction whose CFG production is listed earliest in the grammar. There are two ways to manually choose which reduction to apply:
- Click on a CFG production from the list of available reductions, on the left side of the main window. The reduction based on that production will be applied to the top of the stack. - Click on one of the stack elements. A popup window will appear, containing all available reductions. Select one, and it will be applied to the top of the stack.
Note that reductions can only be applied to the top of the stack.
Keyboard Shortcuts:: [Space]\t Perform the next shift or reduce operation [s]\t Perform a shift operation [r]\t Perform a reduction operation [Ctrl-z]\t Undo most recent operation [Delete]\t Reset the parser [g]\t Show/hide available production list [Ctrl-a]\t Toggle animations [h]\t Help [Ctrl-p]\t Print [q]\t Quit """
""" Possible future improvements: - button/window to change and/or select text. Just pop up a window with an entry, and let them modify the text; and then retokenize it? Maybe give a warning if it contains tokens whose types are not in the grammar. - button/window to change and/or select grammar. Select from several alternative grammars? Or actually change the grammar? If the later, then I'd want to define nltk.draw.cfg, which would be responsible for that. """
Scrollbar, Tk)
""" A graphical tool for exploring the shift-reduce parser. The tool displays the parser's stack and the remaining text, and allows the user to control the parser's operation. In particular, the user can shift tokens onto the stack, and can perform reductions on the top elements of the stack. A "step" button simply steps through the parsing process, performing the operations that ``nltk.parse.ShiftReduceParser`` would use. """ 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'] = ''
######################################### ## Initialization Helpers #########################################
# See: <http://www.astro.washington.edu/owen/ROTKFolklore.html> self._sysfont = tkFont.Font(font=Button()["font"]) root.option_add("*Font", self._sysfont)
# TWhat's our font size (default=same as sysfont) self._size = IntVar(root) self._size.set(self._sysfont.cget('size'))
self._boldfont = tkFont.Font(family='helvetica', weight='bold', size=self._size.get()) self._font = tkFont.Font(family='helvetica', size=self._size.get())
# Grammar view. self._prodframe = listframe = Frame(parent) self._prodframe.pack(fill='both', side='left', padx=2) self._prodlist_label = Label(self._prodframe, font=self._boldfont, text='Available Reductions') self._prodlist_label.pack() self._prodlist = Listbox(self._prodframe, selectmode='single', relief='groove', background='white', foreground='#909090', font=self._font, selectforeground='#004040', selectbackground='#c0f0c0')
self._prodlist.pack(side='right', fill='both', expand=1)
self._productions = list(self._parser.grammar().productions()) for production in self._productions: self._prodlist.insert('end', (' %s' % production)) self._prodlist.config(height=min(len(self._productions), 25))
# Add a scrollbar if there are more than 25 productions. if 1:#len(self._productions) > 25: listscroll = Scrollbar(self._prodframe, orient='vertical') self._prodlist.config(yscrollcommand = listscroll.set) listscroll.config(command=self._prodlist.yview) listscroll.pack(side='left', fill='y')
# If they select a production, apply it. self._prodlist.bind('<<ListboxSelect>>', self._prodlist_select)
# When they hover over a production, highlight it. self._hover = -1 self._prodlist.bind('<Motion>', self._highlight_hover) self._prodlist.bind('<Leave>', self._clear_hover)
# Quit self._top.bind('<Control-q>', self.destroy) self._top.bind('<Control-x>', self.destroy) self._top.bind('<Alt-q>', self.destroy) self._top.bind('<Alt-x>', self.destroy)
# Ops (step, shift, reduce, undo) self._top.bind('<space>', self.step) self._top.bind('<s>', self.shift) self._top.bind('<Alt-s>', self.shift) self._top.bind('<Control-s>', self.shift) self._top.bind('<r>', self.reduce) self._top.bind('<Alt-r>', self.reduce) self._top.bind('<Control-r>', self.reduce) self._top.bind('<Delete>', self.reset) self._top.bind('<u>', self.undo) self._top.bind('<Alt-u>', self.undo) self._top.bind('<Control-u>', self.undo) self._top.bind('<Control-z>', self.undo) self._top.bind('<BackSpace>', self.undo)
# Misc self._top.bind('<Control-p>', self.postscript) self._top.bind('<Control-h>', self.help) self._top.bind('<F1>', self.help) self._top.bind('<Control-g>', self.edit_grammar) self._top.bind('<Control-t>', self.edit_sentence)
# Animation speed control self._top.bind('-', lambda e,a=self._animate:a.set(20)) self._top.bind('=', lambda e,a=self._animate:a.set(10)) self._top.bind('+', lambda e,a=self._animate:a.set(4))
# Set up the frames. self._buttonframe = buttonframe = Frame(parent) buttonframe.pack(fill='none', side='bottom') Button(buttonframe, text='Step', background='#90c0d0', foreground='black', command=self.step,).pack(side='left') Button(buttonframe, text='Shift', underline=0, background='#90f090', foreground='black', command=self.shift).pack(side='left') Button(buttonframe, text='Reduce', underline=0, background='#90f090', foreground='black', command=self.reduce).pack(side='left') Button(buttonframe, text='Undo', underline=0, background='#f0a0a0', foreground='black', command=self.undo).pack(side='left')
menubar = Menu(parent)
filemenu = Menu(menubar, tearoff=0) filemenu.add_command(label='Reset Parser', underline=0, command=self.reset, accelerator='Del') filemenu.add_command(label='Print to Postscript', underline=0, command=self.postscript, accelerator='Ctrl-p') filemenu.add_command(label='Exit', underline=1, command=self.destroy, accelerator='Ctrl-x') menubar.add_cascade(label='File', underline=0, menu=filemenu)
editmenu = Menu(menubar, tearoff=0) editmenu.add_command(label='Edit Grammar', underline=5, command=self.edit_grammar, accelerator='Ctrl-g') editmenu.add_command(label='Edit Text', underline=5, command=self.edit_sentence, accelerator='Ctrl-t') menubar.add_cascade(label='Edit', underline=0, menu=editmenu)
rulemenu = Menu(menubar, tearoff=0) rulemenu.add_command(label='Step', underline=1, command=self.step, accelerator='Space') rulemenu.add_separator() rulemenu.add_command(label='Shift', underline=0, command=self.shift, accelerator='Ctrl-s') rulemenu.add_command(label='Reduce', underline=0, command=self.reduce, accelerator='Ctrl-r') rulemenu.add_separator() rulemenu.add_command(label='Undo', underline=0, command=self.undo, accelerator='Ctrl-u') menubar.add_cascade(label='Apply', underline=0, menu=rulemenu)
viewmenu = Menu(menubar, tearoff=0) viewmenu.add_checkbutton(label="Show Grammar", underline=0, variable=self._show_grammar, command=self._toggle_grammar) viewmenu.add_separator() viewmenu.add_radiobutton(label='Tiny', variable=self._size, underline=0, value=10, command=self.resize) viewmenu.add_radiobutton(label='Small', variable=self._size, underline=0, value=12, command=self.resize) viewmenu.add_radiobutton(label='Medium', variable=self._size, underline=0, value=14, command=self.resize) viewmenu.add_radiobutton(label='Large', variable=self._size, underline=0, value=18, command=self.resize) viewmenu.add_radiobutton(label='Huge', variable=self._size, underline=0, value=24, command=self.resize) menubar.add_cascade(label='View', underline=0, menu=viewmenu)
animatemenu = Menu(menubar, tearoff=0) animatemenu.add_radiobutton(label="No Animation", underline=0, variable=self._animate, value=0) animatemenu.add_radiobutton(label="Slow Animation", underline=0, variable=self._animate, value=20, accelerator='-') animatemenu.add_radiobutton(label="Normal Animation", underline=0, variable=self._animate, value=10, accelerator='=') animatemenu.add_radiobutton(label="Fast Animation", underline=0, variable=self._animate, value=4, accelerator='+') menubar.add_cascade(label="Animate", underline=1, menu=animatemenu)
helpmenu = Menu(menubar, tearoff=0) helpmenu.add_command(label='About', underline=0, command=self.about) helpmenu.add_command(label='Instructions', underline=0, command=self.help, accelerator='F1') menubar.add_cascade(label='Help', underline=0, menu=helpmenu)
parent.config(menu=menubar)
self._feedbackframe = feedbackframe = Frame(parent) feedbackframe.pack(fill='x', side='bottom', padx=3, pady=3) self._lastoper_label = Label(feedbackframe, text='Last Operation:', font=self._font) self._lastoper_label.pack(side='left') lastoperframe = Frame(feedbackframe, relief='sunken', border=1) lastoperframe.pack(fill='x', side='right', expand=1, padx=5) self._lastoper1 = Label(lastoperframe, foreground='#007070', background='#f0f0f0', font=self._font) self._lastoper2 = Label(lastoperframe, anchor='w', width=30, foreground='#004040', background='#f0f0f0', font=self._font) self._lastoper1.pack(side='left') self._lastoper2.pack(side='left', fill='x', expand=1)
self._cframe = CanvasFrame(parent, background='white', width=525, closeenough=10, border=2, relief='sunken') self._cframe.pack(expand=1, fill='both', side='top', pady=2) canvas = self._canvas = self._cframe.canvas()
self._stackwidgets = [] self._rtextwidgets = [] self._titlebar = canvas.create_rectangle(0,0,0,0, fill='#c0f0f0', outline='black') self._exprline = canvas.create_line(0,0,0,0, dash='.') self._stacktop = canvas.create_line(0,0,0,0, fill='#408080') size = self._size.get()+4 self._stacklabel = TextWidget(canvas, 'Stack', color='#004040', font=self._boldfont) self._rtextlabel = TextWidget(canvas, 'Remaining Text', color='#004040', font=self._boldfont) self._cframe.add_widget(self._stacklabel) self._cframe.add_widget(self._rtextlabel)
######################################### ## Main draw procedure #########################################
scrollregion = self._canvas['scrollregion'].split() (cx1, cy1, cx2, cy2) = [int(c) for c in scrollregion]
# Delete the old stack & rtext widgets. for stackwidget in self._stackwidgets: self._cframe.destroy_widget(stackwidget) self._stackwidgets = [] for rtextwidget in self._rtextwidgets: self._cframe.destroy_widget(rtextwidget) self._rtextwidgets = []
# Position the titlebar & exprline (x1, y1, x2, y2) = self._stacklabel.bbox() y = y2-y1+10 self._canvas.coords(self._titlebar, -5000, 0, 5000, y-4) self._canvas.coords(self._exprline, 0, y*2-10, 5000, y*2-10)
# Position the titlebar labels.. (x1, y1, x2, y2) = self._stacklabel.bbox() self._stacklabel.move(5-x1, 3-y1) (x1, y1, x2, y2) = self._rtextlabel.bbox() self._rtextlabel.move(cx2-x2-5, 3-y1)
# Draw the stack. stackx = 5 for tok in self._parser.stack(): if isinstance(tok, Tree): attribs = {'tree_color': '#4080a0', 'tree_width': 2, 'node_font': self._boldfont, 'node_color': '#006060', 'leaf_color': '#006060', 'leaf_font':self._font} widget = tree_to_treesegment(self._canvas, tok, **attribs) widget.node()['color'] = '#000000' else: widget = TextWidget(self._canvas, tok, color='#000000', font=self._font) widget.bind_click(self._popup_reduce) self._stackwidgets.append(widget) self._cframe.add_widget(widget, stackx, y) stackx = widget.bbox()[2] + 10
# Draw the remaining text. rtextwidth = 0 for tok in self._parser.remaining_text(): widget = TextWidget(self._canvas, tok, color='#000000', font=self._font) self._rtextwidgets.append(widget) self._cframe.add_widget(widget, rtextwidth, y) rtextwidth = widget.bbox()[2] + 4
# Allow enough room to shift the next token (for animations) if len(self._rtextwidgets) > 0: stackx += self._rtextwidgets[0].width()
# Move the remaining text to the correct location (keep it # right-justified, when possible); and move the remaining text # label, if necessary. stackx = max(stackx, self._stacklabel.width()+25) rlabelwidth = self._rtextlabel.width()+10 if stackx >= cx2-max(rtextwidth, rlabelwidth): cx2 = stackx + max(rtextwidth, rlabelwidth) for rtextwidget in self._rtextwidgets: rtextwidget.move(4+cx2-rtextwidth, 0) self._rtextlabel.move(cx2-self._rtextlabel.bbox()[2]-5, 0)
midx = (stackx + cx2-max(rtextwidth, rlabelwidth))/2 self._canvas.coords(self._stacktop, midx, 0, midx, 5000) (x1, y1, x2, y2) = self._stacklabel.bbox()
# Set up binding to allow them to shift a token by dragging it. if len(self._rtextwidgets) > 0: def drag_shift(widget, midx=midx, self=self): if widget.bbox()[0] < midx: self.shift() else: self._redraw() self._rtextwidgets[0].bind_drag(drag_shift) self._rtextwidgets[0].bind_click(self.shift)
# Draw the stack top. self._highlight_productions()
# hack.. midx = widget.bbox()[2]+50 self._canvas.coords(self._stacktop, midx, 0, midx, 5000)
# Highlight the productions that can be reduced. self._prodlist.selection_clear(0, 'end') for prod in self._parser.reducible_productions(): index = self._productions.index(prod) self._prodlist.selection_set(index)
######################################### ## Button Callbacks #########################################
if self._top is None: return self._top.destroy() self._top = None
self._parser.initialize(self._sent) self._lastoper1['text'] = 'Reset App' self._lastoper2['text'] = '' self._redraw()
if self.reduce(): return 1 elif self.shift(): return 1 else: if len(self._parser.parses()) > 0: self._lastoper1['text'] = 'Finished:' self._lastoper2['text'] = 'Success' else: self._lastoper1['text'] = 'Finished:' self._lastoper2['text'] = 'Failure'
if self._animating_lock: return if self._parser.shift(): tok = self._parser.stack()[-1] self._lastoper1['text'] = 'Shift:' self._lastoper2['text'] = '%r' % tok if self._animate.get(): self._animate_shift() else: self._redraw() return 1 return 0
if self._animating_lock: return production = self._parser.reduce() if production: self._lastoper1['text'] = 'Reduce:' self._lastoper2['text'] = '%s' % production if self._animate.get(): self._animate_reduce() else: self._redraw() return production
if self._animating_lock: return if self._parser.undo(): self._redraw()
self._cframe.print_to_file()
""" Enter the Tkinter mainloop. This function must be called if this demo is created from a non-interactive program (e.g. from a secript); otherwise, the demo will close as soon as the script completes. """ if in_idle(): return self._top.mainloop(*args, **kwargs)
######################################### ## Menubar callbacks #########################################
if size is not None: self._size.set(size) size = self._size.get() self._font.configure(size=-(abs(size))) self._boldfont.configure(size=-(abs(size))) self._sysfont.configure(size=-(abs(size)))
#self._stacklabel['font'] = ('helvetica', -size-4, 'bold') #self._rtextlabel['font'] = ('helvetica', -size-4, 'bold') #self._lastoper_label['font'] = ('helvetica', -size) #self._lastoper1['font'] = ('helvetica', -size) #self._lastoper2['font'] = ('helvetica', -size) #self._prodlist['font'] = ('helvetica', -size) #self._prodlist_label['font'] = ('helvetica', -size-2, 'bold') self._redraw()
# The default font's not very legible; try using 'fixed' instead. try: ShowText(self._top, 'Help: Shift-Reduce Parser Application', (__doc__).strip(), width=75, font='fixed') except: ShowText(self._top, 'Help: Shift-Reduce Parser Application', (__doc__).strip(), width=75)
ABOUT = ("NLTK Shift-Reduce Parser Application\n"+ "Written by Edward Loper") TITLE = 'About: Shift-Reduce Parser Application' try: from tkMessageBox import Message Message(message=ABOUT, title=TITLE).show() except: ShowText(self._top, TITLE, ABOUT)
CFGEditor(self._top, self._parser.grammar(), self.set_grammar)
self._parser.set_grammar(grammar) self._productions = list(grammar.productions()) self._prodlist.delete(0, 'end') for production in self._productions: self._prodlist.insert('end', (' %s' % production))
sentence = " ".join(self._sent) title = 'Edit Text' instr = 'Enter a new sentence to parse.' EntryDialog(self._top, sentence, instr, self.set_sentence, title)
self._sent = sent.split() #[XX] use tagged? self.reset()
######################################### ## Reduce Production Selection #########################################
if self._show_grammar.get(): self._prodframe.pack(fill='both', side='left', padx=2, after=self._feedbackframe) self._lastoper1['text'] = 'Show Grammar' else: self._prodframe.pack_forget() self._lastoper1['text'] = 'Hide Grammar' self._lastoper2['text'] = ''
selection = self._prodlist.curselection() if len(selection) != 1: return index = int(selection[0]) production = self._parser.reduce(self._productions[index]) if production: self._lastoper1['text'] = 'Reduce:' self._lastoper2['text'] = '%s' % production if self._animate.get(): self._animate_reduce() else: self._redraw() else: # Reset the production selections. self._prodlist.selection_clear(0, 'end') for prod in self._parser.reducible_productions(): index = self._productions.index(prod) self._prodlist.selection_set(index)
# Remove old commands. productions = self._parser.reducible_productions() if len(productions) == 0: return
self._reduce_menu.delete(0, 'end') for production in productions: self._reduce_menu.add_command(label=str(production), command=self.reduce) self._reduce_menu.post(self._canvas.winfo_pointerx(), self._canvas.winfo_pointery())
######################################### ## Animations #########################################
# What widget are we shifting? widget = self._rtextwidgets[0]
# Where are we shifting from & to? right = widget.bbox()[0] if len(self._stackwidgets) == 0: left = 5 else: left = self._stackwidgets[-1].bbox()[2]+10
# Start animating. dt = self._animate.get() dx = (left-right)*1.0/dt self._animate_shift_frame(dt, widget, dx)
if frame > 0: self._animating_lock = 1 widget.move(dx, 0) self._top.after(10, self._animate_shift_frame, frame-1, widget, dx) else: # but: stacktop??
# Shift the widget to the stack. del self._rtextwidgets[0] self._stackwidgets.append(widget) self._animating_lock = 0
# Display the available productions. self._draw_stack_top(widget) self._highlight_productions()
# What widgets are we shifting? numwidgets = len(self._parser.stack()[-1]) # number of children widgets = self._stackwidgets[-numwidgets:]
# How far are we moving? if isinstance(widgets[0], TreeSegmentWidget): ydist = 15 + widgets[0].node().height() else: ydist = 15 + widgets[0].height()
# Start animating. dt = self._animate.get() dy = ydist*2.0/dt self._animate_reduce_frame(dt/2, widgets, dy)
if frame > 0: self._animating_lock = 1 for widget in widgets: widget.move(0, dy) self._top.after(10, self._animate_reduce_frame, frame-1, widgets, dy) else: del self._stackwidgets[-len(widgets):] for widget in widgets: self._cframe.remove_widget(widget) tok = self._parser.stack()[-1] if not isinstance(tok, Tree): raise ValueError() label = TextWidget(self._canvas, str(tok.node), color='#006060', font=self._boldfont) widget = TreeSegmentWidget(self._canvas, label, widgets, width=2) (x1, y1, x2, y2) = self._stacklabel.bbox() y = y2-y1+10 if not self._stackwidgets: x = 5 else: x = self._stackwidgets[-1].bbox()[2] + 10 self._cframe.add_widget(widget, x, y) self._stackwidgets.append(widget)
# Display the available productions. self._draw_stack_top(widget) self._highlight_productions()
# # Delete the old widgets.. # del self._stackwidgets[-len(widgets):] # for widget in widgets: # self._cframe.destroy_widget(widget) # # # Make a new one. # tok = self._parser.stack()[-1] # if isinstance(tok, Tree): # attribs = {'tree_color': '#4080a0', 'tree_width': 2, # 'node_font': bold, 'node_color': '#006060', # 'leaf_color': '#006060', 'leaf_font':self._font} # widget = tree_to_treesegment(self._canvas, tok.type(), # **attribs) # widget.node()['color'] = '#000000' # else: # widget = TextWidget(self._canvas, tok.type(), # color='#000000', font=self._font) # widget.bind_click(self._popup_reduce) # (x1, y1, x2, y2) = self._stacklabel.bbox() # y = y2-y1+10 # if not self._stackwidgets: x = 5 # else: x = self._stackwidgets[-1].bbox()[2] + 10 # self._cframe.add_widget(widget, x, y) # self._stackwidgets.append(widget)
#self._redraw() self._animating_lock = 0
######################################### ## Hovering. #########################################
# What production are we hovering over? index = self._prodlist.nearest(event.y) if self._hover == index: return
# Clear any previous hover highlighting. self._clear_hover()
# If the production corresponds to an available reduction, # highlight the stack. selection = [int(s) for s in self._prodlist.curselection()] if index in selection: rhslen = len(self._productions[index].rhs()) for stackwidget in self._stackwidgets[-rhslen:]: if isinstance(stackwidget, TreeSegmentWidget): stackwidget.node()['color'] = '#00a000' else: stackwidget['color'] = '#00a000'
# Remember what production we're hovering over. self._hover = index
# Clear any previous hover highlighting. if self._hover == -1: return self._hover = -1 for stackwidget in self._stackwidgets: if isinstance(stackwidget, TreeSegmentWidget): stackwidget.node()['color'] = 'black' else: stackwidget['color'] = 'black'
""" Create a shift reduce parser app, using a simple grammar and text. """
from nltk.grammar import Nonterminal, Production, ContextFreeGrammar nonterminals = 'S VP NP PP P N Name V Det' (S, VP, NP, PP, P, N, Name, V, Det) = [Nonterminal(s) for s in nonterminals.split()]
productions = ( # Syntactic Productions Production(S, [NP, VP]), Production(NP, [Det, N]), Production(NP, [NP, PP]), Production(VP, [VP, PP]), Production(VP, [V, NP, PP]), Production(VP, [V, NP]), Production(PP, [P, NP]),
# Lexical Productions Production(NP, ['I']), Production(Det, ['the']), Production(Det, ['a']), Production(N, ['man']), Production(V, ['saw']), Production(P, ['in']), Production(P, ['with']), Production(N, ['park']), Production(N, ['dog']), Production(N, ['statue']), Production(Det, ['my']), )
grammar = ContextFreeGrammar(S, productions)
# tokenize the sentence sent = 'my dog saw a man in the park with a statue'.split()
ShiftReduceApp(grammar, sent).mainloop()
app()
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