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@@ -1088,3 +1088,4 @@ infer_4_37_2/lib/libubsan.so.1.0.0 filter=lfs diff=lfs merge=lfs -text
 infer_4_37_2/lib/libtinfow.so.6 filter=lfs diff=lfs merge=lfs -text
 infer_4_33_0/lib/python3.10/site-packages/scipy/ndimage/_ni_label.cpython-310-x86_64-linux-gnu.so filter=lfs diff=lfs merge=lfs -text
 evalkit_tf446/lib/python3.10/site-packages/nvidia/cudnn/lib/libcudnn_ops.so.9 filter=lfs diff=lfs merge=lfs -text
+infer_4_37_2/lib/python3.10/site-packages/nltk/corpus/reader/__pycache__/framenet.cpython-310.pyc filter=lfs diff=lfs merge=lfs -text

infer_4_37_2/lib/python3.10/site-packages/nltk/app/chartparser_app.py

@@ -0,0 +1,2569 @@
+# Natural Language Toolkit: Chart Parser Application
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Edward Loper <[email protected]>
+#         Jean Mark Gawron <[email protected]>
+#         Steven Bird <[email protected]>
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+A graphical tool for exploring chart parsing.
+
+Chart parsing is a flexible parsing algorithm that uses a data
+structure called a "chart" to record hypotheses about syntactic
+constituents.  Each hypothesis is represented by a single "edge" on
+the chart.  A set of "chart rules" determine when new edges can be
+added to the chart.  This set of rules controls the overall behavior
+of the parser (e.g. whether it parses top-down or bottom-up).
+
+The chart parsing tool demonstrates the process of parsing a single
+sentence, with a given grammar and lexicon.  Its display is divided
+into three sections: the bottom section displays the chart; the middle
+section displays the sentence; and the top section displays the
+partial syntax tree corresponding to the selected edge.  Buttons along
+the bottom of the window are used to control the execution of the
+algorithm.
+
+The chart parsing tool allows for flexible control of the parsing
+algorithm.  At each step of the algorithm, you can select which rule
+or strategy you wish to apply.  This allows you to experiment with
+mixing different strategies (e.g. top-down and bottom-up).  You can
+exercise fine-grained control over the algorithm by selecting which
+edge you wish to apply a rule to.
+"""
+
+# At some point, we should rewrite this tool to use the new canvas
+# widget system.
+
+
+import os.path
+import pickle
+from tkinter import (
+    Button,
+    Canvas,
+    Checkbutton,
+    Frame,
+    IntVar,
+    Label,
+    Menu,
+    Scrollbar,
+    Tk,
+    Toplevel,
+)
+from tkinter.filedialog import askopenfilename, asksaveasfilename
+from tkinter.font import Font
+from tkinter.messagebox import showerror, showinfo
+
+from nltk.draw import CFGEditor, TreeSegmentWidget, tree_to_treesegment
+from nltk.draw.util import (
+    CanvasFrame,
+    ColorizedList,
+    EntryDialog,
+    MutableOptionMenu,
+    ShowText,
+    SymbolWidget,
+)
+from nltk.grammar import CFG, Nonterminal
+from nltk.parse.chart import (
+    BottomUpPredictCombineRule,
+    BottomUpPredictRule,
+    Chart,
+    LeafEdge,
+    LeafInitRule,
+    SingleEdgeFundamentalRule,
+    SteppingChartParser,
+    TopDownInitRule,
+    TopDownPredictRule,
+    TreeEdge,
+)
+from nltk.tree import Tree
+from nltk.util import in_idle
+
+# Known bug: ChartView doesn't handle edges generated by epsilon
+# productions (e.g., [Production: PP -> ]) very well.
+
+#######################################################################
+# Edge List
+#######################################################################
+
+
+class EdgeList(ColorizedList):
+    ARROW = SymbolWidget.SYMBOLS["rightarrow"]
+
+    def _init_colortags(self, textwidget, options):
+        textwidget.tag_config("terminal", foreground="#006000")
+        textwidget.tag_config("arrow", font="symbol", underline="0")
+        textwidget.tag_config("dot", foreground="#000000")
+        textwidget.tag_config(
+            "nonterminal", foreground="blue", font=("helvetica", -12, "bold")
+        )
+
+    def _item_repr(self, item):
+        contents = []
+        contents.append(("%s\t" % item.lhs(), "nonterminal"))
+        contents.append((self.ARROW, "arrow"))
+        for i, elt in enumerate(item.rhs()):
+            if i == item.dot():
+                contents.append((" *", "dot"))
+            if isinstance(elt, Nonterminal):
+                contents.append((" %s" % elt.symbol(), "nonterminal"))
+            else:
+                contents.append((" %r" % elt, "terminal"))
+        if item.is_complete():
+            contents.append((" *", "dot"))
+        return contents
+
+
+#######################################################################
+# Chart Matrix View
+#######################################################################
+
+
+class ChartMatrixView:
+    """
+    A view of a chart that displays the contents of the corresponding matrix.
+    """
+
+    def __init__(
+        self, parent, chart, toplevel=True, title="Chart Matrix", show_numedges=False
+    ):
+        self._chart = chart
+        self._cells = []
+        self._marks = []
+
+        self._selected_cell = None
+
+        if toplevel:
+            self._root = Toplevel(parent)
+            self._root.title(title)
+            self._root.bind("<Control-q>", self.destroy)
+            self._init_quit(self._root)
+        else:
+            self._root = Frame(parent)
+
+        self._init_matrix(self._root)
+        self._init_list(self._root)
+        if show_numedges:
+            self._init_numedges(self._root)
+        else:
+            self._numedges_label = None
+
+        self._callbacks = {}
+
+        self._num_edges = 0
+
+        self.draw()
+
+    def _init_quit(self, root):
+        quit = Button(root, text="Quit", command=self.destroy)
+        quit.pack(side="bottom", expand=0, fill="none")
+
+    def _init_matrix(self, root):
+        cframe = Frame(root, border=2, relief="sunken")
+        cframe.pack(expand=0, fill="none", padx=1, pady=3, side="top")
+        self._canvas = Canvas(cframe, width=200, height=200, background="white")
+        self._canvas.pack(expand=0, fill="none")
+
+    def _init_numedges(self, root):
+        self._numedges_label = Label(root, text="0 edges")
+        self._numedges_label.pack(expand=0, fill="none", side="top")
+
+    def _init_list(self, root):
+        self._list = EdgeList(root, [], width=20, height=5)
+        self._list.pack(side="top", expand=1, fill="both", pady=3)
+
+        def cb(edge, self=self):
+            self._fire_callbacks("select", edge)
+
+        self._list.add_callback("select", cb)
+        self._list.focus()
+
+    def destroy(self, *e):
+        if self._root is None:
+            return
+        try:
+            self._root.destroy()
+        except:
+            pass
+        self._root = None
+
+    def set_chart(self, chart):
+        if chart is not self._chart:
+            self._chart = chart
+            self._num_edges = 0
+            self.draw()
+
+    def update(self):
+        if self._root is None:
+            return
+
+        # Count the edges in each cell
+        N = len(self._cells)
+        cell_edges = [[0 for i in range(N)] for j in range(N)]
+        for edge in self._chart:
+            cell_edges[edge.start()][edge.end()] += 1
+
+        # Color the cells correspondingly.
+        for i in range(N):
+            for j in range(i, N):
+                if cell_edges[i][j] == 0:
+                    color = "gray20"
+                else:
+                    color = "#00{:02x}{:02x}".format(
+                        min(255, 50 + 128 * cell_edges[i][j] / 10),
+                        max(0, 128 - 128 * cell_edges[i][j] / 10),
+                    )
+                cell_tag = self._cells[i][j]
+                self._canvas.itemconfig(cell_tag, fill=color)
+                if (i, j) == self._selected_cell:
+                    self._canvas.itemconfig(cell_tag, outline="#00ffff", width=3)
+                    self._canvas.tag_raise(cell_tag)
+                else:
+                    self._canvas.itemconfig(cell_tag, outline="black", width=1)
+
+        # Update the edge list.
+        edges = list(self._chart.select(span=self._selected_cell))
+        self._list.set(edges)
+
+        # Update our edge count.
+        self._num_edges = self._chart.num_edges()
+        if self._numedges_label is not None:
+            self._numedges_label["text"] = "%d edges" % self._num_edges
+
+    def activate(self):
+        self._canvas.itemconfig("inactivebox", state="hidden")
+        self.update()
+
+    def inactivate(self):
+        self._canvas.itemconfig("inactivebox", state="normal")
+        self.update()
+
+    def add_callback(self, event, func):
+        self._callbacks.setdefault(event, {})[func] = 1
+
+    def remove_callback(self, event, func=None):
+        if func is None:
+            del self._callbacks[event]
+        else:
+            try:
+                del self._callbacks[event][func]
+            except:
+                pass
+
+    def _fire_callbacks(self, event, *args):
+        if event not in self._callbacks:
+            return
+        for cb_func in list(self._callbacks[event].keys()):
+            cb_func(*args)
+
+    def select_cell(self, i, j):
+        if self._root is None:
+            return
+
+        # If the cell is already selected (and the chart contents
+        # haven't changed), then do nothing.
+        if (i, j) == self._selected_cell and self._chart.num_edges() == self._num_edges:
+            return
+
+        self._selected_cell = (i, j)
+        self.update()
+
+        # Fire the callback.
+        self._fire_callbacks("select_cell", i, j)
+
+    def deselect_cell(self):
+        if self._root is None:
+            return
+        self._selected_cell = None
+        self._list.set([])
+        self.update()
+
+    def _click_cell(self, i, j):
+        if self._selected_cell == (i, j):
+            self.deselect_cell()
+        else:
+            self.select_cell(i, j)
+
+    def view_edge(self, edge):
+        self.select_cell(*edge.span())
+        self._list.view(edge)
+
+    def mark_edge(self, edge):
+        if self._root is None:
+            return
+        self.select_cell(*edge.span())
+        self._list.mark(edge)
+
+    def unmark_edge(self, edge=None):
+        if self._root is None:
+            return
+        self._list.unmark(edge)
+
+    def markonly_edge(self, edge):
+        if self._root is None:
+            return
+        self.select_cell(*edge.span())
+        self._list.markonly(edge)
+
+    def draw(self):
+        if self._root is None:
+            return
+        LEFT_MARGIN = BOT_MARGIN = 15
+        TOP_MARGIN = 5
+        c = self._canvas
+        c.delete("all")
+        N = self._chart.num_leaves() + 1
+        dx = (int(c["width"]) - LEFT_MARGIN) / N
+        dy = (int(c["height"]) - TOP_MARGIN - BOT_MARGIN) / N
+
+        c.delete("all")
+
+        # Labels and dotted lines
+        for i in range(N):
+            c.create_text(
+                LEFT_MARGIN - 2, i * dy + dy / 2 + TOP_MARGIN, text=repr(i), anchor="e"
+            )
+            c.create_text(
+                i * dx + dx / 2 + LEFT_MARGIN,
+                N * dy + TOP_MARGIN + 1,
+                text=repr(i),
+                anchor="n",
+            )
+            c.create_line(
+                LEFT_MARGIN,
+                dy * (i + 1) + TOP_MARGIN,
+                dx * N + LEFT_MARGIN,
+                dy * (i + 1) + TOP_MARGIN,
+                dash=".",
+            )
+            c.create_line(
+                dx * i + LEFT_MARGIN,
+                TOP_MARGIN,
+                dx * i + LEFT_MARGIN,
+                dy * N + TOP_MARGIN,
+                dash=".",
+            )
+
+        # A box around the whole thing
+        c.create_rectangle(
+            LEFT_MARGIN, TOP_MARGIN, LEFT_MARGIN + dx * N, dy * N + TOP_MARGIN, width=2
+        )
+
+        # Cells
+        self._cells = [[None for i in range(N)] for j in range(N)]
+        for i in range(N):
+            for j in range(i, N):
+                t = c.create_rectangle(
+                    j * dx + LEFT_MARGIN,
+                    i * dy + TOP_MARGIN,
+                    (j + 1) * dx + LEFT_MARGIN,
+                    (i + 1) * dy + TOP_MARGIN,
+                    fill="gray20",
+                )
+                self._cells[i][j] = t
+
+                def cb(event, self=self, i=i, j=j):
+                    self._click_cell(i, j)
+
+                c.tag_bind(t, "<Button-1>", cb)
+
+        # Inactive box
+        xmax, ymax = int(c["width"]), int(c["height"])
+        t = c.create_rectangle(
+            -100,
+            -100,
+            xmax + 100,
+            ymax + 100,
+            fill="gray50",
+            state="hidden",
+            tag="inactivebox",
+        )
+        c.tag_lower(t)
+
+        # Update the cells.
+        self.update()
+
+    def pack(self, *args, **kwargs):
+        self._root.pack(*args, **kwargs)
+
+
+#######################################################################
+# Chart Results View
+#######################################################################
+
+
+class ChartResultsView:
+    def __init__(self, parent, chart, grammar, toplevel=True):
+        self._chart = chart
+        self._grammar = grammar
+        self._trees = []
+        self._y = 10
+        self._treewidgets = []
+        self._selection = None
+        self._selectbox = None
+
+        if toplevel:
+            self._root = Toplevel(parent)
+            self._root.title("Chart Parser Application: Results")
+            self._root.bind("<Control-q>", self.destroy)
+        else:
+            self._root = Frame(parent)
+
+        # Buttons
+        if toplevel:
+            buttons = Frame(self._root)
+            buttons.pack(side="bottom", expand=0, fill="x")
+            Button(buttons, text="Quit", command=self.destroy).pack(side="right")
+            Button(buttons, text="Print All", command=self.print_all).pack(side="left")
+            Button(buttons, text="Print Selection", command=self.print_selection).pack(
+                side="left"
+            )
+
+        # Canvas frame.
+        self._cframe = CanvasFrame(self._root, closeenough=20)
+        self._cframe.pack(side="top", expand=1, fill="both")
+
+        # Initial update
+        self.update()
+
+    def update(self, edge=None):
+        if self._root is None:
+            return
+        # If the edge isn't a parse edge, do nothing.
+        if edge is not None:
+            if edge.lhs() != self._grammar.start():
+                return
+            if edge.span() != (0, self._chart.num_leaves()):
+                return
+
+        for parse in self._chart.parses(self._grammar.start()):
+            if parse not in self._trees:
+                self._add(parse)
+
+    def _add(self, parse):
+        # Add it to self._trees.
+        self._trees.append(parse)
+
+        # Create a widget for it.
+        c = self._cframe.canvas()
+        treewidget = tree_to_treesegment(c, parse)
+
+        # Add it to the canvas frame.
+        self._treewidgets.append(treewidget)
+        self._cframe.add_widget(treewidget, 10, self._y)
+
+        # Register callbacks.
+        treewidget.bind_click(self._click)
+
+        # Update y.
+        self._y = treewidget.bbox()[3] + 10
+
+    def _click(self, widget):
+        c = self._cframe.canvas()
+        if self._selection is not None:
+            c.delete(self._selectbox)
+        self._selection = widget
+        (x1, y1, x2, y2) = widget.bbox()
+        self._selectbox = c.create_rectangle(x1, y1, x2, y2, width=2, outline="#088")
+
+    def _color(self, treewidget, color):
+        treewidget.label()["color"] = color
+        for child in treewidget.subtrees():
+            if isinstance(child, TreeSegmentWidget):
+                self._color(child, color)
+            else:
+                child["color"] = color
+
+    def print_all(self, *e):
+        if self._root is None:
+            return
+        self._cframe.print_to_file()
+
+    def print_selection(self, *e):
+        if self._root is None:
+            return
+        if self._selection is None:
+            showerror("Print Error", "No tree selected")
+        else:
+            c = self._cframe.canvas()
+            for widget in self._treewidgets:
+                if widget is not self._selection:
+                    self._cframe.destroy_widget(widget)
+            c.delete(self._selectbox)
+            (x1, y1, x2, y2) = self._selection.bbox()
+            self._selection.move(10 - x1, 10 - y1)
+            c["scrollregion"] = f"0 0 {x2 - x1 + 20} {y2 - y1 + 20}"
+            self._cframe.print_to_file()
+
+            # Restore our state.
+            self._treewidgets = [self._selection]
+            self.clear()
+            self.update()
+
+    def clear(self):
+        if self._root is None:
+            return
+        for treewidget in self._treewidgets:
+            self._cframe.destroy_widget(treewidget)
+        self._trees = []
+        self._treewidgets = []
+        if self._selection is not None:
+            self._cframe.canvas().delete(self._selectbox)
+        self._selection = None
+        self._y = 10
+
+    def set_chart(self, chart):
+        self.clear()
+        self._chart = chart
+        self.update()
+
+    def set_grammar(self, grammar):
+        self.clear()
+        self._grammar = grammar
+        self.update()
+
+    def destroy(self, *e):
+        if self._root is None:
+            return
+        try:
+            self._root.destroy()
+        except:
+            pass
+        self._root = None
+
+    def pack(self, *args, **kwargs):
+        self._root.pack(*args, **kwargs)
+
+
+#######################################################################
+# Chart Comparer
+#######################################################################
+
+
+class ChartComparer:
+    """
+
+    :ivar _root: The root window
+
+    :ivar _charts: A dictionary mapping names to charts.  When
+        charts are loaded, they are added to this dictionary.
+
+    :ivar _left_chart: The left ``Chart``.
+    :ivar _left_name: The name ``_left_chart`` (derived from filename)
+    :ivar _left_matrix: The ``ChartMatrixView`` for ``_left_chart``
+    :ivar _left_selector: The drop-down ``MutableOptionsMenu`` used
+          to select ``_left_chart``.
+
+    :ivar _right_chart: The right ``Chart``.
+    :ivar _right_name: The name ``_right_chart`` (derived from filename)
+    :ivar _right_matrix: The ``ChartMatrixView`` for ``_right_chart``
+    :ivar _right_selector: The drop-down ``MutableOptionsMenu`` used
+          to select ``_right_chart``.
+
+    :ivar _out_chart: The out ``Chart``.
+    :ivar _out_name: The name ``_out_chart`` (derived from filename)
+    :ivar _out_matrix: The ``ChartMatrixView`` for ``_out_chart``
+    :ivar _out_label: The label for ``_out_chart``.
+
+    :ivar _op_label: A Label containing the most recent operation.
+    """
+
+    _OPSYMBOL = {
+        "-": "-",
+        "and": SymbolWidget.SYMBOLS["intersection"],
+        "or": SymbolWidget.SYMBOLS["union"],
+    }
+
+    def __init__(self, *chart_filenames):
+        # This chart is displayed when we don't have a value (eg
+        # before any chart is loaded).
+        faketok = [""] * 8
+        self._emptychart = Chart(faketok)
+
+        # The left & right charts start out empty.
+        self._left_name = "None"
+        self._right_name = "None"
+        self._left_chart = self._emptychart
+        self._right_chart = self._emptychart
+
+        # The charts that have been loaded.
+        self._charts = {"None": self._emptychart}
+
+        # The output chart.
+        self._out_chart = self._emptychart
+
+        # The most recent operation
+        self._operator = None
+
+        # Set up the root window.
+        self._root = Tk()
+        self._root.title("Chart Comparison")
+        self._root.bind("<Control-q>", self.destroy)
+        self._root.bind("<Control-x>", self.destroy)
+
+        # Initialize all widgets, etc.
+        self._init_menubar(self._root)
+        self._init_chartviews(self._root)
+        self._init_divider(self._root)
+        self._init_buttons(self._root)
+        self._init_bindings(self._root)
+
+        # Load any specified charts.
+        for filename in chart_filenames:
+            self.load_chart(filename)
+
+    def destroy(self, *e):
+        if self._root is None:
+            return
+        try:
+            self._root.destroy()
+        except:
+            pass
+        self._root = None
+
+    def mainloop(self, *args, **kwargs):
+        return
+        self._root.mainloop(*args, **kwargs)
+
+    # ////////////////////////////////////////////////////////////
+    # Initialization
+    # ////////////////////////////////////////////////////////////
+
+    def _init_menubar(self, root):
+        menubar = Menu(root)
+
+        # File menu
+        filemenu = Menu(menubar, tearoff=0)
+        filemenu.add_command(
+            label="Load Chart",
+            accelerator="Ctrl-o",
+            underline=0,
+            command=self.load_chart_dialog,
+        )
+        filemenu.add_command(
+            label="Save Output",
+            accelerator="Ctrl-s",
+            underline=0,
+            command=self.save_chart_dialog,
+        )
+        filemenu.add_separator()
+        filemenu.add_command(
+            label="Exit", underline=1, command=self.destroy, accelerator="Ctrl-x"
+        )
+        menubar.add_cascade(label="File", underline=0, menu=filemenu)
+
+        # Compare menu
+        opmenu = Menu(menubar, tearoff=0)
+        opmenu.add_command(
+            label="Intersection", command=self._intersection, accelerator="+"
+        )
+        opmenu.add_command(label="Union", command=self._union, accelerator="*")
+        opmenu.add_command(
+            label="Difference", command=self._difference, accelerator="-"
+        )
+        opmenu.add_separator()
+        opmenu.add_command(label="Swap Charts", command=self._swapcharts)
+        menubar.add_cascade(label="Compare", underline=0, menu=opmenu)
+
+        # Add the menu
+        self._root.config(menu=menubar)
+
+    def _init_divider(self, root):
+        divider = Frame(root, border=2, relief="sunken")
+        divider.pack(side="top", fill="x", ipady=2)
+
+    def _init_chartviews(self, root):
+        opfont = ("symbol", -36)  # Font for operator.
+        eqfont = ("helvetica", -36)  # Font for equals sign.
+
+        frame = Frame(root, background="#c0c0c0")
+        frame.pack(side="top", expand=1, fill="both")
+
+        # The left matrix.
+        cv1_frame = Frame(frame, border=3, relief="groove")
+        cv1_frame.pack(side="left", padx=8, pady=7, expand=1, fill="both")
+        self._left_selector = MutableOptionMenu(
+            cv1_frame, list(self._charts.keys()), command=self._select_left
+        )
+        self._left_selector.pack(side="top", pady=5, fill="x")
+        self._left_matrix = ChartMatrixView(
+            cv1_frame, self._emptychart, toplevel=False, show_numedges=True
+        )
+        self._left_matrix.pack(side="bottom", padx=5, pady=5, expand=1, fill="both")
+        self._left_matrix.add_callback("select", self.select_edge)
+        self._left_matrix.add_callback("select_cell", self.select_cell)
+        self._left_matrix.inactivate()
+
+        # The operator.
+        self._op_label = Label(
+            frame, text=" ", width=3, background="#c0c0c0", font=opfont
+        )
+        self._op_label.pack(side="left", padx=5, pady=5)
+
+        # The right matrix.
+        cv2_frame = Frame(frame, border=3, relief="groove")
+        cv2_frame.pack(side="left", padx=8, pady=7, expand=1, fill="both")
+        self._right_selector = MutableOptionMenu(
+            cv2_frame, list(self._charts.keys()), command=self._select_right
+        )
+        self._right_selector.pack(side="top", pady=5, fill="x")
+        self._right_matrix = ChartMatrixView(
+            cv2_frame, self._emptychart, toplevel=False, show_numedges=True
+        )
+        self._right_matrix.pack(side="bottom", padx=5, pady=5, expand=1, fill="both")
+        self._right_matrix.add_callback("select", self.select_edge)
+        self._right_matrix.add_callback("select_cell", self.select_cell)
+        self._right_matrix.inactivate()
+
+        # The equals sign
+        Label(frame, text="=", width=3, background="#c0c0c0", font=eqfont).pack(
+            side="left", padx=5, pady=5
+        )
+
+        # The output matrix.
+        out_frame = Frame(frame, border=3, relief="groove")
+        out_frame.pack(side="left", padx=8, pady=7, expand=1, fill="both")
+        self._out_label = Label(out_frame, text="Output")
+        self._out_label.pack(side="top", pady=9)
+        self._out_matrix = ChartMatrixView(
+            out_frame, self._emptychart, toplevel=False, show_numedges=True
+        )
+        self._out_matrix.pack(side="bottom", padx=5, pady=5, expand=1, fill="both")
+        self._out_matrix.add_callback("select", self.select_edge)
+        self._out_matrix.add_callback("select_cell", self.select_cell)
+        self._out_matrix.inactivate()
+
+    def _init_buttons(self, root):
+        buttons = Frame(root)
+        buttons.pack(side="bottom", pady=5, fill="x", expand=0)
+        Button(buttons, text="Intersection", command=self._intersection).pack(
+            side="left"
+        )
+        Button(buttons, text="Union", command=self._union).pack(side="left")
+        Button(buttons, text="Difference", command=self._difference).pack(side="left")
+        Frame(buttons, width=20).pack(side="left")
+        Button(buttons, text="Swap Charts", command=self._swapcharts).pack(side="left")
+
+        Button(buttons, text="Detach Output", command=self._detach_out).pack(
+            side="right"
+        )
+
+    def _init_bindings(self, root):
+        # root.bind('<Control-s>', self.save_chart)
+        root.bind("<Control-o>", self.load_chart_dialog)
+        # root.bind('<Control-r>', self.reset)
+
+    # ////////////////////////////////////////////////////////////
+    # Input Handling
+    # ////////////////////////////////////////////////////////////
+
+    def _select_left(self, name):
+        self._left_name = name
+        self._left_chart = self._charts[name]
+        self._left_matrix.set_chart(self._left_chart)
+        if name == "None":
+            self._left_matrix.inactivate()
+        self._apply_op()
+
+    def _select_right(self, name):
+        self._right_name = name
+        self._right_chart = self._charts[name]
+        self._right_matrix.set_chart(self._right_chart)
+        if name == "None":
+            self._right_matrix.inactivate()
+        self._apply_op()
+
+    def _apply_op(self):
+        if self._operator == "-":
+            self._difference()
+        elif self._operator == "or":
+            self._union()
+        elif self._operator == "and":
+            self._intersection()
+
+    # ////////////////////////////////////////////////////////////
+    # File
+    # ////////////////////////////////////////////////////////////
+    CHART_FILE_TYPES = [("Pickle file", ".pickle"), ("All files", "*")]
+
+    def save_chart_dialog(self, *args):
+        filename = asksaveasfilename(
+            filetypes=self.CHART_FILE_TYPES, defaultextension=".pickle"
+        )
+        if not filename:
+            return
+        try:
+            with open(filename, "wb") as outfile:
+                pickle.dump(self._out_chart, outfile)
+        except Exception as e:
+            showerror("Error Saving Chart", f"Unable to open file: {filename!r}\n{e}")
+
+    def load_chart_dialog(self, *args):
+        filename = askopenfilename(
+            filetypes=self.CHART_FILE_TYPES, defaultextension=".pickle"
+        )
+        if not filename:
+            return
+        try:
+            self.load_chart(filename)
+        except Exception as e:
+            showerror("Error Loading Chart", f"Unable to open file: {filename!r}\n{e}")
+
+    def load_chart(self, filename):
+        with open(filename, "rb") as infile:
+            chart = pickle.load(infile)
+        name = os.path.basename(filename)
+        if name.endswith(".pickle"):
+            name = name[:-7]
+        if name.endswith(".chart"):
+            name = name[:-6]
+        self._charts[name] = chart
+        self._left_selector.add(name)
+        self._right_selector.add(name)
+
+        # If either left_matrix or right_matrix is empty, then
+        # display the new chart.
+        if self._left_chart is self._emptychart:
+            self._left_selector.set(name)
+        elif self._right_chart is self._emptychart:
+            self._right_selector.set(name)
+
+    def _update_chartviews(self):
+        self._left_matrix.update()
+        self._right_matrix.update()
+        self._out_matrix.update()
+
+    # ////////////////////////////////////////////////////////////
+    # Selection
+    # ////////////////////////////////////////////////////////////
+
+    def select_edge(self, edge):
+        if edge in self._left_chart:
+            self._left_matrix.markonly_edge(edge)
+        else:
+            self._left_matrix.unmark_edge()
+        if edge in self._right_chart:
+            self._right_matrix.markonly_edge(edge)
+        else:
+            self._right_matrix.unmark_edge()
+        if edge in self._out_chart:
+            self._out_matrix.markonly_edge(edge)
+        else:
+            self._out_matrix.unmark_edge()
+
+    def select_cell(self, i, j):
+        self._left_matrix.select_cell(i, j)
+        self._right_matrix.select_cell(i, j)
+        self._out_matrix.select_cell(i, j)
+
+    # ////////////////////////////////////////////////////////////
+    # Operations
+    # ////////////////////////////////////////////////////////////
+
+    def _difference(self):
+        if not self._checkcompat():
+            return
+
+        out_chart = Chart(self._left_chart.tokens())
+        for edge in self._left_chart:
+            if edge not in self._right_chart:
+                out_chart.insert(edge, [])
+
+        self._update("-", out_chart)
+
+    def _intersection(self):
+        if not self._checkcompat():
+            return
+
+        out_chart = Chart(self._left_chart.tokens())
+        for edge in self._left_chart:
+            if edge in self._right_chart:
+                out_chart.insert(edge, [])
+
+        self._update("and", out_chart)
+
+    def _union(self):
+        if not self._checkcompat():
+            return
+
+        out_chart = Chart(self._left_chart.tokens())
+        for edge in self._left_chart:
+            out_chart.insert(edge, [])
+        for edge in self._right_chart:
+            out_chart.insert(edge, [])
+
+        self._update("or", out_chart)
+
+    def _swapcharts(self):
+        left, right = self._left_name, self._right_name
+        self._left_selector.set(right)
+        self._right_selector.set(left)
+
+    def _checkcompat(self):
+        if (
+            self._left_chart.tokens() != self._right_chart.tokens()
+            or self._left_chart.property_names() != self._right_chart.property_names()
+            or self._left_chart == self._emptychart
+            or self._right_chart == self._emptychart
+        ):
+            # Clear & inactivate the output chart.
+            self._out_chart = self._emptychart
+            self._out_matrix.set_chart(self._out_chart)
+            self._out_matrix.inactivate()
+            self._out_label["text"] = "Output"
+            # Issue some other warning?
+            return False
+        else:
+            return True
+
+    def _update(self, operator, out_chart):
+        self._operator = operator
+        self._op_label["text"] = self._OPSYMBOL[operator]
+        self._out_chart = out_chart
+        self._out_matrix.set_chart(out_chart)
+        self._out_label["text"] = "{} {} {}".format(
+            self._left_name,
+            self._operator,
+            self._right_name,
+        )
+
+    def _clear_out_chart(self):
+        self._out_chart = self._emptychart
+        self._out_matrix.set_chart(self._out_chart)
+        self._op_label["text"] = " "
+        self._out_matrix.inactivate()
+
+    def _detach_out(self):
+        ChartMatrixView(self._root, self._out_chart, title=self._out_label["text"])
+
+
+#######################################################################
+# Chart View
+#######################################################################
+
+
+class ChartView:
+    """
+    A component for viewing charts.  This is used by ``ChartParserApp`` to
+    allow students to interactively experiment with various chart
+    parsing techniques.  It is also used by ``Chart.draw()``.
+
+    :ivar _chart: The chart that we are giving a view of.  This chart
+       may be modified; after it is modified, you should call
+       ``update``.
+    :ivar _sentence: The list of tokens that the chart spans.
+
+    :ivar _root: The root window.
+    :ivar _chart_canvas: The canvas we're using to display the chart
+        itself.
+    :ivar _tree_canvas: The canvas we're using to display the tree
+        that each edge spans.  May be None, if we're not displaying
+        trees.
+    :ivar _sentence_canvas: The canvas we're using to display the sentence
+        text.  May be None, if we're not displaying the sentence text.
+    :ivar _edgetags: A dictionary mapping from edges to the tags of
+        the canvas elements (lines, etc) used to display that edge.
+        The values of this dictionary have the form
+        ``(linetag, rhstag1, dottag, rhstag2, lhstag)``.
+    :ivar _treetags: A list of all the tags that make up the tree;
+        used to erase the tree (without erasing the loclines).
+    :ivar _chart_height: The height of the chart canvas.
+    :ivar _sentence_height: The height of the sentence canvas.
+    :ivar _tree_height: The height of the tree
+
+    :ivar _text_height: The height of a text string (in the normal
+        font).
+
+    :ivar _edgelevels: A list of edges at each level of the chart (the
+        top level is the 0th element).  This list is used to remember
+        where edges should be drawn; and to make sure that no edges
+        are overlapping on the chart view.
+
+    :ivar _unitsize: Pixel size of one unit (from the location).  This
+       is determined by the span of the chart's location, and the
+       width of the chart display canvas.
+
+    :ivar _fontsize: The current font size
+
+    :ivar _marks: A dictionary from edges to marks.  Marks are
+        strings, specifying colors (e.g. 'green').
+    """
+
+    _LEAF_SPACING = 10
+    _MARGIN = 10
+    _TREE_LEVEL_SIZE = 12
+    _CHART_LEVEL_SIZE = 40
+
+    def __init__(self, chart, root=None, **kw):
+        """
+        Construct a new ``Chart`` display.
+        """
+        # Process keyword args.
+        draw_tree = kw.get("draw_tree", 0)
+        draw_sentence = kw.get("draw_sentence", 1)
+        self._fontsize = kw.get("fontsize", -12)
+
+        # The chart!
+        self._chart = chart
+
+        # Callback functions
+        self._callbacks = {}
+
+        # Keep track of drawn edges
+        self._edgelevels = []
+        self._edgetags = {}
+
+        # Keep track of which edges are marked.
+        self._marks = {}
+
+        # These are used to keep track of the set of tree tokens
+        # currently displayed in the tree canvas.
+        self._treetoks = []
+        self._treetoks_edge = None
+        self._treetoks_index = 0
+
+        # Keep track of the tags used to draw the tree
+        self._tree_tags = []
+
+        # Put multiple edges on each level?
+        self._compact = 0
+
+        # If they didn't provide a main window, then set one up.
+        if root is None:
+            top = Tk()
+            top.title("Chart View")
+
+            def destroy1(e, top=top):
+                top.destroy()
+
+            def destroy2(top=top):
+                top.destroy()
+
+            top.bind("q", destroy1)
+            b = Button(top, text="Done", command=destroy2)
+            b.pack(side="bottom")
+            self._root = top
+        else:
+            self._root = root
+
+        # Create some fonts.
+        self._init_fonts(root)
+
+        # Create the chart canvas.
+        (self._chart_sb, self._chart_canvas) = self._sb_canvas(self._root)
+        self._chart_canvas["height"] = 300
+        self._chart_canvas["closeenough"] = 15
+
+        # Create the sentence canvas.
+        if draw_sentence:
+            cframe = Frame(self._root, relief="sunk", border=2)
+            cframe.pack(fill="both", side="bottom")
+            self._sentence_canvas = Canvas(cframe, height=50)
+            self._sentence_canvas["background"] = "#e0e0e0"
+            self._sentence_canvas.pack(fill="both")
+            # self._sentence_canvas['height'] = self._sentence_height
+        else:
+            self._sentence_canvas = None
+
+        # Create the tree canvas.
+        if draw_tree:
+            (sb, canvas) = self._sb_canvas(self._root, "n", "x")
+            (self._tree_sb, self._tree_canvas) = (sb, canvas)
+            self._tree_canvas["height"] = 200
+        else:
+            self._tree_canvas = None
+
+        # Do some analysis to figure out how big the window should be
+        self._analyze()
+        self.draw()
+        self._resize()
+        self._grow()
+
+        # Set up the configure callback, which will be called whenever
+        # the window is resized.
+        self._chart_canvas.bind("<Configure>", self._configure)
+
+    def _init_fonts(self, root):
+        self._boldfont = Font(family="helvetica", weight="bold", size=self._fontsize)
+        self._font = Font(family="helvetica", size=self._fontsize)
+        # See: <http://www.astro.washington.edu/owen/ROTKFolklore.html>
+        self._sysfont = Font(font=Button()["font"])
+        root.option_add("*Font", self._sysfont)
+
+    def _sb_canvas(self, root, expand="y", fill="both", side="bottom"):
+        """
+        Helper for __init__: construct a canvas with a scrollbar.
+        """
+        cframe = Frame(root, relief="sunk", border=2)
+        cframe.pack(fill=fill, expand=expand, side=side)
+        canvas = Canvas(cframe, background="#e0e0e0")
+
+        # Give the canvas a scrollbar.
+        sb = Scrollbar(cframe, orient="vertical")
+        sb.pack(side="right", fill="y")
+        canvas.pack(side="left", fill=fill, expand="yes")
+
+        # Connect the scrollbars to the canvas.
+        sb["command"] = canvas.yview
+        canvas["yscrollcommand"] = sb.set
+
+        return (sb, canvas)
+
+    def scroll_up(self, *e):
+        self._chart_canvas.yview("scroll", -1, "units")
+
+    def scroll_down(self, *e):
+        self._chart_canvas.yview("scroll", 1, "units")
+
+    def page_up(self, *e):
+        self._chart_canvas.yview("scroll", -1, "pages")
+
+    def page_down(self, *e):
+        self._chart_canvas.yview("scroll", 1, "pages")
+
+    def _grow(self):
+        """
+        Grow the window, if necessary
+        """
+        # Grow, if need-be
+        N = self._chart.num_leaves()
+        width = max(
+            int(self._chart_canvas["width"]), N * self._unitsize + ChartView._MARGIN * 2
+        )
+
+        # It won't resize without the second (height) line, but I
+        # don't understand why not.
+        self._chart_canvas.configure(width=width)
+        self._chart_canvas.configure(height=self._chart_canvas["height"])
+
+        self._unitsize = (width - 2 * ChartView._MARGIN) / N
+
+        # Reset the height for the sentence window.
+        if self._sentence_canvas is not None:
+            self._sentence_canvas["height"] = self._sentence_height
+
+    def set_font_size(self, size):
+        self._font.configure(size=-abs(size))
+        self._boldfont.configure(size=-abs(size))
+        self._sysfont.configure(size=-abs(size))
+        self._analyze()
+        self._grow()
+        self.draw()
+
+    def get_font_size(self):
+        return abs(self._fontsize)
+
+    def _configure(self, e):
+        """
+        The configure callback.  This is called whenever the window is
+        resized.  It is also called when the window is first mapped.
+        It figures out the unit size, and redraws the contents of each
+        canvas.
+        """
+        N = self._chart.num_leaves()
+        self._unitsize = (e.width - 2 * ChartView._MARGIN) / N
+        self.draw()
+
+    def update(self, chart=None):
+        """
+        Draw any edges that have not been drawn.  This is typically
+        called when a after modifies the canvas that a CanvasView is
+        displaying.  ``update`` will cause any edges that have been
+        added to the chart to be drawn.
+
+        If update is given a ``chart`` argument, then it will replace
+        the current chart with the given chart.
+        """
+        if chart is not None:
+            self._chart = chart
+            self._edgelevels = []
+            self._marks = {}
+            self._analyze()
+            self._grow()
+            self.draw()
+            self.erase_tree()
+            self._resize()
+        else:
+            for edge in self._chart:
+                if edge not in self._edgetags:
+                    self._add_edge(edge)
+            self._resize()
+
+    def _edge_conflict(self, edge, lvl):
+        """
+        Return True if the given edge overlaps with any edge on the given
+        level.  This is used by _add_edge to figure out what level a
+        new edge should be added to.
+        """
+        (s1, e1) = edge.span()
+        for otheredge in self._edgelevels[lvl]:
+            (s2, e2) = otheredge.span()
+            if (s1 <= s2 < e1) or (s2 <= s1 < e2) or (s1 == s2 == e1 == e2):
+                return True
+        return False
+
+    def _analyze_edge(self, edge):
+        """
+        Given a new edge, recalculate:
+
+            - _text_height
+            - _unitsize (if the edge text is too big for the current
+              _unitsize, then increase _unitsize)
+        """
+        c = self._chart_canvas
+
+        if isinstance(edge, TreeEdge):
+            lhs = edge.lhs()
+            rhselts = []
+            for elt in edge.rhs():
+                if isinstance(elt, Nonterminal):
+                    rhselts.append(str(elt.symbol()))
+                else:
+                    rhselts.append(repr(elt))
+            rhs = " ".join(rhselts)
+        else:
+            lhs = edge.lhs()
+            rhs = ""
+
+        for s in (lhs, rhs):
+            tag = c.create_text(
+                0, 0, text=s, font=self._boldfont, anchor="nw", justify="left"
+            )
+            bbox = c.bbox(tag)
+            c.delete(tag)
+            width = bbox[2]  # + ChartView._LEAF_SPACING
+            edgelen = max(edge.length(), 1)
+            self._unitsize = max(self._unitsize, width / edgelen)
+            self._text_height = max(self._text_height, bbox[3] - bbox[1])
+
+    def _add_edge(self, edge, minlvl=0):
+        """
+        Add a single edge to the ChartView:
+
+            - Call analyze_edge to recalculate display parameters
+            - Find an available level
+            - Call _draw_edge
+        """
+        # Do NOT show leaf edges in the chart.
+        if isinstance(edge, LeafEdge):
+            return
+
+        if edge in self._edgetags:
+            return
+        self._analyze_edge(edge)
+        self._grow()
+
+        if not self._compact:
+            self._edgelevels.append([edge])
+            lvl = len(self._edgelevels) - 1
+            self._draw_edge(edge, lvl)
+            self._resize()
+            return
+
+        # Figure out what level to draw the edge on.
+        lvl = 0
+        while True:
+            # If this level doesn't exist yet, create it.
+            while lvl >= len(self._edgelevels):
+                self._edgelevels.append([])
+                self._resize()
+
+            # Check if we can fit the edge in this level.
+            if lvl >= minlvl and not self._edge_conflict(edge, lvl):
+                # Go ahead and draw it.
+                self._edgelevels[lvl].append(edge)
+                break
+
+            # Try the next level.
+            lvl += 1
+
+        self._draw_edge(edge, lvl)
+
+    def view_edge(self, edge):
+        level = None
+        for i in range(len(self._edgelevels)):
+            if edge in self._edgelevels[i]:
+                level = i
+                break
+        if level is None:
+            return
+        # Try to view the new edge..
+        y = (level + 1) * self._chart_level_size
+        dy = self._text_height + 10
+        self._chart_canvas.yview("moveto", 1.0)
+        if self._chart_height != 0:
+            self._chart_canvas.yview("moveto", (y - dy) / self._chart_height)
+
+    def _draw_edge(self, edge, lvl):
+        """
+        Draw a single edge on the ChartView.
+        """
+        c = self._chart_canvas
+
+        # Draw the arrow.
+        x1 = edge.start() * self._unitsize + ChartView._MARGIN
+        x2 = edge.end() * self._unitsize + ChartView._MARGIN
+        if x2 == x1:
+            x2 += max(4, self._unitsize / 5)
+        y = (lvl + 1) * self._chart_level_size
+        linetag = c.create_line(x1, y, x2, y, arrow="last", width=3)
+
+        # Draw a label for the edge.
+        if isinstance(edge, TreeEdge):
+            rhs = []
+            for elt in edge.rhs():
+                if isinstance(elt, Nonterminal):
+                    rhs.append(str(elt.symbol()))
+                else:
+                    rhs.append(repr(elt))
+            pos = edge.dot()
+        else:
+            rhs = []
+            pos = 0
+
+        rhs1 = " ".join(rhs[:pos])
+        rhs2 = " ".join(rhs[pos:])
+        rhstag1 = c.create_text(x1 + 3, y, text=rhs1, font=self._font, anchor="nw")
+        dotx = c.bbox(rhstag1)[2] + 6
+        doty = (c.bbox(rhstag1)[1] + c.bbox(rhstag1)[3]) / 2
+        dottag = c.create_oval(dotx - 2, doty - 2, dotx + 2, doty + 2)
+        rhstag2 = c.create_text(dotx + 6, y, text=rhs2, font=self._font, anchor="nw")
+        lhstag = c.create_text(
+            (x1 + x2) / 2, y, text=str(edge.lhs()), anchor="s", font=self._boldfont
+        )
+
+        # Keep track of the edge's tags.
+        self._edgetags[edge] = (linetag, rhstag1, dottag, rhstag2, lhstag)
+
+        # Register a callback for clicking on the edge.
+        def cb(event, self=self, edge=edge):
+            self._fire_callbacks("select", edge)
+
+        c.tag_bind(rhstag1, "<Button-1>", cb)
+        c.tag_bind(rhstag2, "<Button-1>", cb)
+        c.tag_bind(linetag, "<Button-1>", cb)
+        c.tag_bind(dottag, "<Button-1>", cb)
+        c.tag_bind(lhstag, "<Button-1>", cb)
+
+        self._color_edge(edge)
+
+    def _color_edge(self, edge, linecolor=None, textcolor=None):
+        """
+        Color in an edge with the given colors.
+        If no colors are specified, use intelligent defaults
+        (dependent on selection, etc.)
+        """
+        if edge not in self._edgetags:
+            return
+        c = self._chart_canvas
+
+        if linecolor is not None and textcolor is not None:
+            if edge in self._marks:
+                linecolor = self._marks[edge]
+            tags = self._edgetags[edge]
+            c.itemconfig(tags[0], fill=linecolor)
+            c.itemconfig(tags[1], fill=textcolor)
+            c.itemconfig(tags[2], fill=textcolor, outline=textcolor)
+            c.itemconfig(tags[3], fill=textcolor)
+            c.itemconfig(tags[4], fill=textcolor)
+            return
+        else:
+            N = self._chart.num_leaves()
+            if edge in self._marks:
+                self._color_edge(self._marks[edge])
+            if edge.is_complete() and edge.span() == (0, N):
+                self._color_edge(edge, "#084", "#042")
+            elif isinstance(edge, LeafEdge):
+                self._color_edge(edge, "#48c", "#246")
+            else:
+                self._color_edge(edge, "#00f", "#008")
+
+    def mark_edge(self, edge, mark="#0df"):
+        """
+        Mark an edge
+        """
+        self._marks[edge] = mark
+        self._color_edge(edge)
+
+    def unmark_edge(self, edge=None):
+        """
+        Unmark an edge (or all edges)
+        """
+        if edge is None:
+            old_marked_edges = list(self._marks.keys())
+            self._marks = {}
+            for edge in old_marked_edges:
+                self._color_edge(edge)
+        else:
+            del self._marks[edge]
+            self._color_edge(edge)
+
+    def markonly_edge(self, edge, mark="#0df"):
+        self.unmark_edge()
+        self.mark_edge(edge, mark)
+
+    def _analyze(self):
+        """
+        Analyze the sentence string, to figure out how big a unit needs
+        to be, How big the tree should be, etc.
+        """
+        # Figure out the text height and the unit size.
+        unitsize = 70  # min unitsize
+        text_height = 0
+        c = self._chart_canvas
+
+        # Check against all tokens
+        for leaf in self._chart.leaves():
+            tag = c.create_text(
+                0, 0, text=repr(leaf), font=self._font, anchor="nw", justify="left"
+            )
+            bbox = c.bbox(tag)
+            c.delete(tag)
+            width = bbox[2] + ChartView._LEAF_SPACING
+            unitsize = max(width, unitsize)
+            text_height = max(text_height, bbox[3] - bbox[1])
+
+        self._unitsize = unitsize
+        self._text_height = text_height
+        self._sentence_height = self._text_height + 2 * ChartView._MARGIN
+
+        # Check against edges.
+        for edge in self._chart.edges():
+            self._analyze_edge(edge)
+
+        # Size of chart levels
+        self._chart_level_size = self._text_height * 2
+
+        # Default tree size..
+        self._tree_height = 3 * (ChartView._TREE_LEVEL_SIZE + self._text_height)
+
+        # Resize the scrollregions.
+        self._resize()
+
+    def _resize(self):
+        """
+        Update the scroll-regions for each canvas.  This ensures that
+        everything is within a scroll-region, so the user can use the
+        scrollbars to view the entire display.  This does *not*
+        resize the window.
+        """
+        c = self._chart_canvas
+
+        # Reset the chart scroll region
+        width = self._chart.num_leaves() * self._unitsize + ChartView._MARGIN * 2
+
+        levels = len(self._edgelevels)
+        self._chart_height = (levels + 2) * self._chart_level_size
+        c["scrollregion"] = (0, 0, width, self._chart_height)
+
+        # Reset the tree scroll region
+        if self._tree_canvas:
+            self._tree_canvas["scrollregion"] = (0, 0, width, self._tree_height)
+
+    def _draw_loclines(self):
+        """
+        Draw location lines.  These are vertical gridlines used to
+        show where each location unit is.
+        """
+        BOTTOM = 50000
+        c1 = self._tree_canvas
+        c2 = self._sentence_canvas
+        c3 = self._chart_canvas
+        margin = ChartView._MARGIN
+        self._loclines = []
+        for i in range(0, self._chart.num_leaves() + 1):
+            x = i * self._unitsize + margin
+
+            if c1:
+                t1 = c1.create_line(x, 0, x, BOTTOM)
+                c1.tag_lower(t1)
+            if c2:
+                t2 = c2.create_line(x, 0, x, self._sentence_height)
+                c2.tag_lower(t2)
+            t3 = c3.create_line(x, 0, x, BOTTOM)
+            c3.tag_lower(t3)
+            t4 = c3.create_text(x + 2, 0, text=repr(i), anchor="nw", font=self._font)
+            c3.tag_lower(t4)
+            # if i % 4 == 0:
+            #    if c1: c1.itemconfig(t1, width=2, fill='gray60')
+            #    if c2: c2.itemconfig(t2, width=2, fill='gray60')
+            #    c3.itemconfig(t3, width=2, fill='gray60')
+            if i % 2 == 0:
+                if c1:
+                    c1.itemconfig(t1, fill="gray60")
+                if c2:
+                    c2.itemconfig(t2, fill="gray60")
+                c3.itemconfig(t3, fill="gray60")
+            else:
+                if c1:
+                    c1.itemconfig(t1, fill="gray80")
+                if c2:
+                    c2.itemconfig(t2, fill="gray80")
+                c3.itemconfig(t3, fill="gray80")
+
+    def _draw_sentence(self):
+        """Draw the sentence string."""
+        if self._chart.num_leaves() == 0:
+            return
+        c = self._sentence_canvas
+        margin = ChartView._MARGIN
+        y = ChartView._MARGIN
+
+        for i, leaf in enumerate(self._chart.leaves()):
+            x1 = i * self._unitsize + margin
+            x2 = x1 + self._unitsize
+            x = (x1 + x2) / 2
+            tag = c.create_text(
+                x, y, text=repr(leaf), font=self._font, anchor="n", justify="left"
+            )
+            bbox = c.bbox(tag)
+            rt = c.create_rectangle(
+                x1 + 2,
+                bbox[1] - (ChartView._LEAF_SPACING / 2),
+                x2 - 2,
+                bbox[3] + (ChartView._LEAF_SPACING / 2),
+                fill="#f0f0f0",
+                outline="#f0f0f0",
+            )
+            c.tag_lower(rt)
+
+    def erase_tree(self):
+        for tag in self._tree_tags:
+            self._tree_canvas.delete(tag)
+        self._treetoks = []
+        self._treetoks_edge = None
+        self._treetoks_index = 0
+
+    def draw_tree(self, edge=None):
+        if edge is None and self._treetoks_edge is None:
+            return
+        if edge is None:
+            edge = self._treetoks_edge
+
+        # If it's a new edge, then get a new list of treetoks.
+        if self._treetoks_edge != edge:
+            self._treetoks = [t for t in self._chart.trees(edge) if isinstance(t, Tree)]
+            self._treetoks_edge = edge
+            self._treetoks_index = 0
+
+        # Make sure there's something to draw.
+        if len(self._treetoks) == 0:
+            return
+
+        # Erase the old tree.
+        for tag in self._tree_tags:
+            self._tree_canvas.delete(tag)
+
+        # Draw the new tree.
+        tree = self._treetoks[self._treetoks_index]
+        self._draw_treetok(tree, edge.start())
+
+        # Show how many trees are available for the edge.
+        self._draw_treecycle()
+
+        # Update the scroll region.
+        w = self._chart.num_leaves() * self._unitsize + 2 * ChartView._MARGIN
+        h = tree.height() * (ChartView._TREE_LEVEL_SIZE + self._text_height)
+        self._tree_canvas["scrollregion"] = (0, 0, w, h)
+
+    def cycle_tree(self):
+        self._treetoks_index = (self._treetoks_index + 1) % len(self._treetoks)
+        self.draw_tree(self._treetoks_edge)
+
+    def _draw_treecycle(self):
+        if len(self._treetoks) <= 1:
+            return
+
+        # Draw the label.
+        label = "%d Trees" % len(self._treetoks)
+        c = self._tree_canvas
+        margin = ChartView._MARGIN
+        right = self._chart.num_leaves() * self._unitsize + margin - 2
+        tag = c.create_text(right, 2, anchor="ne", text=label, font=self._boldfont)
+        self._tree_tags.append(tag)
+        _, _, _, y = c.bbox(tag)
+
+        # Draw the triangles.
+        for i in range(len(self._treetoks)):
+            x = right - 20 * (len(self._treetoks) - i - 1)
+            if i == self._treetoks_index:
+                fill = "#084"
+            else:
+                fill = "#fff"
+            tag = c.create_polygon(
+                x, y + 10, x - 5, y, x - 10, y + 10, fill=fill, outline="black"
+            )
+            self._tree_tags.append(tag)
+
+            # Set up a callback: show the tree if they click on its
+            # triangle.
+            def cb(event, self=self, i=i):
+                self._treetoks_index = i
+                self.draw_tree()
+
+            c.tag_bind(tag, "<Button-1>", cb)
+
+    def _draw_treetok(self, treetok, index, depth=0):
+        """
+        :param index: The index of the first leaf in the tree.
+        :return: The index of the first leaf after the tree.
+        """
+        c = self._tree_canvas
+        margin = ChartView._MARGIN
+
+        # Draw the children
+        child_xs = []
+        for child in treetok:
+            if isinstance(child, Tree):
+                child_x, index = self._draw_treetok(child, index, depth + 1)
+                child_xs.append(child_x)
+            else:
+                child_xs.append((2 * index + 1) * self._unitsize / 2 + margin)
+                index += 1
+
+        # If we have children, then get the node's x by averaging their
+        # node x's.  Otherwise, make room for ourselves.
+        if child_xs:
+            nodex = sum(child_xs) / len(child_xs)
+        else:
+            # [XX] breaks for null productions.
+            nodex = (2 * index + 1) * self._unitsize / 2 + margin
+            index += 1
+
+        # Draw the node
+        nodey = depth * (ChartView._TREE_LEVEL_SIZE + self._text_height)
+        tag = c.create_text(
+            nodex,
+            nodey,
+            anchor="n",
+            justify="center",
+            text=str(treetok.label()),
+            fill="#042",
+            font=self._boldfont,
+        )
+        self._tree_tags.append(tag)
+
+        # Draw lines to the children.
+        childy = nodey + ChartView._TREE_LEVEL_SIZE + self._text_height
+        for childx, child in zip(child_xs, treetok):
+            if isinstance(child, Tree) and child:
+                # A "real" tree token:
+                tag = c.create_line(
+                    nodex,
+                    nodey + self._text_height,
+                    childx,
+                    childy,
+                    width=2,
+                    fill="#084",
+                )
+                self._tree_tags.append(tag)
+            if isinstance(child, Tree) and not child:
+                # An unexpanded tree token:
+                tag = c.create_line(
+                    nodex,
+                    nodey + self._text_height,
+                    childx,
+                    childy,
+                    width=2,
+                    fill="#048",
+                    dash="2 3",
+                )
+                self._tree_tags.append(tag)
+            if not isinstance(child, Tree):
+                # A leaf:
+                tag = c.create_line(
+                    nodex,
+                    nodey + self._text_height,
+                    childx,
+                    10000,
+                    width=2,
+                    fill="#084",
+                )
+                self._tree_tags.append(tag)
+
+        return nodex, index
+
+    def draw(self):
+        """
+        Draw everything (from scratch).
+        """
+        if self._tree_canvas:
+            self._tree_canvas.delete("all")
+            self.draw_tree()
+
+        if self._sentence_canvas:
+            self._sentence_canvas.delete("all")
+            self._draw_sentence()
+
+        self._chart_canvas.delete("all")
+        self._edgetags = {}
+
+        # Redraw any edges we erased.
+        for lvl in range(len(self._edgelevels)):
+            for edge in self._edgelevels[lvl]:
+                self._draw_edge(edge, lvl)
+
+        for edge in self._chart:
+            self._add_edge(edge)
+
+        self._draw_loclines()
+
+    def add_callback(self, event, func):
+        self._callbacks.setdefault(event, {})[func] = 1
+
+    def remove_callback(self, event, func=None):
+        if func is None:
+            del self._callbacks[event]
+        else:
+            try:
+                del self._callbacks[event][func]
+            except:
+                pass
+
+    def _fire_callbacks(self, event, *args):
+        if event not in self._callbacks:
+            return
+        for cb_func in list(self._callbacks[event].keys()):
+            cb_func(*args)
+
+
+#######################################################################
+# Edge Rules
+#######################################################################
+# These version of the chart rules only apply to a specific edge.
+# This lets the user select an edge, and then apply a rule.
+
+
+class EdgeRule:
+    """
+    To create an edge rule, make an empty base class that uses
+    EdgeRule as the first base class, and the basic rule as the
+    second base class.  (Order matters!)
+    """
+
+    def __init__(self, edge):
+        super = self.__class__.__bases__[1]
+        self._edge = edge
+        self.NUM_EDGES = super.NUM_EDGES - 1
+
+    def apply(self, chart, grammar, *edges):
+        super = self.__class__.__bases__[1]
+        edges += (self._edge,)
+        yield from super.apply(self, chart, grammar, *edges)
+
+    def __str__(self):
+        super = self.__class__.__bases__[1]
+        return super.__str__(self)
+
+
+class TopDownPredictEdgeRule(EdgeRule, TopDownPredictRule):
+    pass
+
+
+class BottomUpEdgeRule(EdgeRule, BottomUpPredictRule):
+    pass
+
+
+class BottomUpLeftCornerEdgeRule(EdgeRule, BottomUpPredictCombineRule):
+    pass
+
+
+class FundamentalEdgeRule(EdgeRule, SingleEdgeFundamentalRule):
+    pass
+
+
+#######################################################################
+# Chart Parser Application
+#######################################################################
+
+
+class ChartParserApp:
+    def __init__(self, grammar, tokens, title="Chart Parser Application"):
+        # Initialize the parser
+        self._init_parser(grammar, tokens)
+
+        self._root = None
+        try:
+            # Create the root window.
+            self._root = Tk()
+            self._root.title(title)
+            self._root.bind("<Control-q>", self.destroy)
+
+            # Set up some frames.
+            frame3 = Frame(self._root)
+            frame2 = Frame(self._root)
+            frame1 = Frame(self._root)
+            frame3.pack(side="bottom", fill="none")
+            frame2.pack(side="bottom", fill="x")
+            frame1.pack(side="bottom", fill="both", expand=1)
+
+            self._init_fonts(self._root)
+            self._init_animation()
+            self._init_chartview(frame1)
+            self._init_rulelabel(frame2)
+            self._init_buttons(frame3)
+            self._init_menubar()
+
+            self._matrix = None
+            self._results = None
+
+            # Set up keyboard bindings.
+            self._init_bindings()
+
+        except:
+            print("Error creating Tree View")
+            self.destroy()
+            raise
+
+    def destroy(self, *args):
+        if self._root is None:
+            return
+        self._root.destroy()
+        self._root = None
+
+    def mainloop(self, *args, **kwargs):
+        """
+        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._root.mainloop(*args, **kwargs)
+
+    # ////////////////////////////////////////////////////////////
+    # Initialization Helpers
+    # ////////////////////////////////////////////////////////////
+
+    def _init_parser(self, grammar, tokens):
+        self._grammar = grammar
+        self._tokens = tokens
+        self._reset_parser()
+
+    def _reset_parser(self):
+        self._cp = SteppingChartParser(self._grammar)
+        self._cp.initialize(self._tokens)
+        self._chart = self._cp.chart()
+
+        # Insert LeafEdges before the parsing starts.
+        for _new_edge in LeafInitRule().apply(self._chart, self._grammar):
+            pass
+
+        # The step iterator -- use this to generate new edges
+        self._cpstep = self._cp.step()
+
+        # The currently selected edge
+        self._selection = None
+
+    def _init_fonts(self, root):
+        # See: <http://www.astro.washington.edu/owen/ROTKFolklore.html>
+        self._sysfont = 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 = Font(family="helvetica", weight="bold", size=self._size.get())
+        self._font = Font(family="helvetica", size=self._size.get())
+
+    def _init_animation(self):
+        # Are we stepping? (default=yes)
+        self._step = IntVar(self._root)
+        self._step.set(1)
+
+        # What's our animation speed (default=fast)
+        self._animate = IntVar(self._root)
+        self._animate.set(3)  # Default speed = fast
+
+        # Are we currently animating?
+        self._animating = 0
+
+    def _init_chartview(self, parent):
+        self._cv = ChartView(self._chart, parent, draw_tree=1, draw_sentence=1)
+        self._cv.add_callback("select", self._click_cv_edge)
+
+    def _init_rulelabel(self, parent):
+        ruletxt = "Last edge generated by:"
+
+        self._rulelabel1 = Label(parent, text=ruletxt, font=self._boldfont)
+        self._rulelabel2 = Label(
+            parent, width=40, relief="groove", anchor="w", font=self._boldfont
+        )
+        self._rulelabel1.pack(side="left")
+        self._rulelabel2.pack(side="left")
+        step = Checkbutton(parent, variable=self._step, text="Step")
+        step.pack(side="right")
+
+    def _init_buttons(self, parent):
+        frame1 = Frame(parent)
+        frame2 = Frame(parent)
+        frame1.pack(side="bottom", fill="x")
+        frame2.pack(side="top", fill="none")
+
+        Button(
+            frame1,
+            text="Reset\nParser",
+            background="#90c0d0",
+            foreground="black",
+            command=self.reset,
+        ).pack(side="right")
+        # Button(frame1, text='Pause',
+        #               background='#90c0d0', foreground='black',
+        #               command=self.pause).pack(side='left')
+
+        Button(
+            frame1,
+            text="Top Down\nStrategy",
+            background="#90c0d0",
+            foreground="black",
+            command=self.top_down_strategy,
+        ).pack(side="left")
+        Button(
+            frame1,
+            text="Bottom Up\nStrategy",
+            background="#90c0d0",
+            foreground="black",
+            command=self.bottom_up_strategy,
+        ).pack(side="left")
+        Button(
+            frame1,
+            text="Bottom Up\nLeft-Corner Strategy",
+            background="#90c0d0",
+            foreground="black",
+            command=self.bottom_up_leftcorner_strategy,
+        ).pack(side="left")
+
+        Button(
+            frame2,
+            text="Top Down Init\nRule",
+            background="#90f090",
+            foreground="black",
+            command=self.top_down_init,
+        ).pack(side="left")
+        Button(
+            frame2,
+            text="Top Down Predict\nRule",
+            background="#90f090",
+            foreground="black",
+            command=self.top_down_predict,
+        ).pack(side="left")
+        Frame(frame2, width=20).pack(side="left")
+
+        Button(
+            frame2,
+            text="Bottom Up Predict\nRule",
+            background="#90f090",
+            foreground="black",
+            command=self.bottom_up,
+        ).pack(side="left")
+        Frame(frame2, width=20).pack(side="left")
+
+        Button(
+            frame2,
+            text="Bottom Up Left-Corner\nPredict Rule",
+            background="#90f090",
+            foreground="black",
+            command=self.bottom_up_leftcorner,
+        ).pack(side="left")
+        Frame(frame2, width=20).pack(side="left")
+
+        Button(
+            frame2,
+            text="Fundamental\nRule",
+            background="#90f090",
+            foreground="black",
+            command=self.fundamental,
+        ).pack(side="left")
+
+    def _init_bindings(self):
+        self._root.bind("<Up>", self._cv.scroll_up)
+        self._root.bind("<Down>", self._cv.scroll_down)
+        self._root.bind("<Prior>", self._cv.page_up)
+        self._root.bind("<Next>", self._cv.page_down)
+        self._root.bind("<Control-q>", self.destroy)
+        self._root.bind("<Control-x>", self.destroy)
+        self._root.bind("<F1>", self.help)
+
+        self._root.bind("<Control-s>", self.save_chart)
+        self._root.bind("<Control-o>", self.load_chart)
+        self._root.bind("<Control-r>", self.reset)
+
+        self._root.bind("t", self.top_down_strategy)
+        self._root.bind("b", self.bottom_up_strategy)
+        self._root.bind("c", self.bottom_up_leftcorner_strategy)
+        self._root.bind("<space>", self._stop_animation)
+
+        self._root.bind("<Control-g>", self.edit_grammar)
+        self._root.bind("<Control-t>", self.edit_sentence)
+
+        # Animation speed control
+        self._root.bind("-", lambda e, a=self._animate: a.set(1))
+        self._root.bind("=", lambda e, a=self._animate: a.set(2))
+        self._root.bind("+", lambda e, a=self._animate: a.set(3))
+
+        # Step control
+        self._root.bind("s", lambda e, s=self._step: s.set(not s.get()))
+
+    def _init_menubar(self):
+        menubar = Menu(self._root)
+
+        filemenu = Menu(menubar, tearoff=0)
+        filemenu.add_command(
+            label="Save Chart",
+            underline=0,
+            command=self.save_chart,
+            accelerator="Ctrl-s",
+        )
+        filemenu.add_command(
+            label="Load Chart",
+            underline=0,
+            command=self.load_chart,
+            accelerator="Ctrl-o",
+        )
+        filemenu.add_command(
+            label="Reset Chart", underline=0, command=self.reset, accelerator="Ctrl-r"
+        )
+        filemenu.add_separator()
+        filemenu.add_command(label="Save Grammar", command=self.save_grammar)
+        filemenu.add_command(label="Load Grammar", command=self.load_grammar)
+        filemenu.add_separator()
+        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)
+
+        viewmenu = Menu(menubar, tearoff=0)
+        viewmenu.add_command(
+            label="Chart Matrix", underline=6, command=self.view_matrix
+        )
+        viewmenu.add_command(label="Results", underline=0, command=self.view_results)
+        menubar.add_cascade(label="View", underline=0, menu=viewmenu)
+
+        rulemenu = Menu(menubar, tearoff=0)
+        rulemenu.add_command(
+            label="Top Down Strategy",
+            underline=0,
+            command=self.top_down_strategy,
+            accelerator="t",
+        )
+        rulemenu.add_command(
+            label="Bottom Up Strategy",
+            underline=0,
+            command=self.bottom_up_strategy,
+            accelerator="b",
+        )
+        rulemenu.add_command(
+            label="Bottom Up Left-Corner Strategy",
+            underline=0,
+            command=self.bottom_up_leftcorner_strategy,
+            accelerator="c",
+        )
+        rulemenu.add_separator()
+        rulemenu.add_command(label="Bottom Up Rule", command=self.bottom_up)
+        rulemenu.add_command(
+            label="Bottom Up Left-Corner Rule", command=self.bottom_up_leftcorner
+        )
+        rulemenu.add_command(label="Top Down Init Rule", command=self.top_down_init)
+        rulemenu.add_command(
+            label="Top Down Predict Rule", command=self.top_down_predict
+        )
+        rulemenu.add_command(label="Fundamental Rule", command=self.fundamental)
+        menubar.add_cascade(label="Apply", underline=0, menu=rulemenu)
+
+        animatemenu = Menu(menubar, tearoff=0)
+        animatemenu.add_checkbutton(
+            label="Step", underline=0, variable=self._step, accelerator="s"
+        )
+        animatemenu.add_separator()
+        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=1,
+            accelerator="-",
+        )
+        animatemenu.add_radiobutton(
+            label="Normal Animation",
+            underline=0,
+            variable=self._animate,
+            value=2,
+            accelerator="=",
+        )
+        animatemenu.add_radiobutton(
+            label="Fast Animation",
+            underline=0,
+            variable=self._animate,
+            value=3,
+            accelerator="+",
+        )
+        menubar.add_cascade(label="Animate", underline=1, menu=animatemenu)
+
+        zoommenu = Menu(menubar, tearoff=0)
+        zoommenu.add_radiobutton(
+            label="Tiny",
+            variable=self._size,
+            underline=0,
+            value=10,
+            command=self.resize,
+        )
+        zoommenu.add_radiobutton(
+            label="Small",
+            variable=self._size,
+            underline=0,
+            value=12,
+            command=self.resize,
+        )
+        zoommenu.add_radiobutton(
+            label="Medium",
+            variable=self._size,
+            underline=0,
+            value=14,
+            command=self.resize,
+        )
+        zoommenu.add_radiobutton(
+            label="Large",
+            variable=self._size,
+            underline=0,
+            value=18,
+            command=self.resize,
+        )
+        zoommenu.add_radiobutton(
+            label="Huge",
+            variable=self._size,
+            underline=0,
+            value=24,
+            command=self.resize,
+        )
+        menubar.add_cascade(label="Zoom", underline=0, menu=zoommenu)
+
+        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)
+
+        self._root.config(menu=menubar)
+
+    # ////////////////////////////////////////////////////////////
+    # Selection Handling
+    # ////////////////////////////////////////////////////////////
+
+    def _click_cv_edge(self, edge):
+        if edge != self._selection:
+            # Clicking on a new edge selects it.
+            self._select_edge(edge)
+        else:
+            # Repeated clicks on one edge cycle its trees.
+            self._cv.cycle_tree()
+            # [XX] this can get confused if animation is running
+            # faster than the callbacks...
+
+    def _select_matrix_edge(self, edge):
+        self._select_edge(edge)
+        self._cv.view_edge(edge)
+
+    def _select_edge(self, edge):
+        self._selection = edge
+        # Update the chart view.
+        self._cv.markonly_edge(edge, "#f00")
+        self._cv.draw_tree(edge)
+        # Update the matrix view.
+        if self._matrix:
+            self._matrix.markonly_edge(edge)
+        if self._matrix:
+            self._matrix.view_edge(edge)
+
+    def _deselect_edge(self):
+        self._selection = None
+        # Update the chart view.
+        self._cv.unmark_edge()
+        self._cv.erase_tree()
+        # Update the matrix view
+        if self._matrix:
+            self._matrix.unmark_edge()
+
+    def _show_new_edge(self, edge):
+        self._display_rule(self._cp.current_chartrule())
+        # Update the chart view.
+        self._cv.update()
+        self._cv.draw_tree(edge)
+        self._cv.markonly_edge(edge, "#0df")
+        self._cv.view_edge(edge)
+        # Update the matrix view.
+        if self._matrix:
+            self._matrix.update()
+        if self._matrix:
+            self._matrix.markonly_edge(edge)
+        if self._matrix:
+            self._matrix.view_edge(edge)
+        # Update the results view.
+        if self._results:
+            self._results.update(edge)
+
+    # ////////////////////////////////////////////////////////////
+    # Help/usage
+    # ////////////////////////////////////////////////////////////
+
+    def help(self, *e):
+        self._animating = 0
+        # The default font's not very legible; try using 'fixed' instead.
+        try:
+            ShowText(
+                self._root,
+                "Help: Chart Parser Application",
+                (__doc__ or "").strip(),
+                width=75,
+                font="fixed",
+            )
+        except:
+            ShowText(
+                self._root,
+                "Help: Chart Parser Application",
+                (__doc__ or "").strip(),
+                width=75,
+            )
+
+    def about(self, *e):
+        ABOUT = "NLTK Chart Parser Application\n" + "Written by Edward Loper"
+        showinfo("About: Chart Parser Application", ABOUT)
+
+    # ////////////////////////////////////////////////////////////
+    # File Menu
+    # ////////////////////////////////////////////////////////////
+
+    CHART_FILE_TYPES = [("Pickle file", ".pickle"), ("All files", "*")]
+    GRAMMAR_FILE_TYPES = [
+        ("Plaintext grammar file", ".cfg"),
+        ("Pickle file", ".pickle"),
+        ("All files", "*"),
+    ]
+
+    def load_chart(self, *args):
+        "Load a chart from a pickle file"
+        filename = askopenfilename(
+            filetypes=self.CHART_FILE_TYPES, defaultextension=".pickle"
+        )
+        if not filename:
+            return
+        try:
+            with open(filename, "rb") as infile:
+                chart = pickle.load(infile)
+            self._chart = chart
+            self._cv.update(chart)
+            if self._matrix:
+                self._matrix.set_chart(chart)
+            if self._matrix:
+                self._matrix.deselect_cell()
+            if self._results:
+                self._results.set_chart(chart)
+            self._cp.set_chart(chart)
+        except Exception as e:
+            raise
+            showerror("Error Loading Chart", "Unable to open file: %r" % filename)
+
+    def save_chart(self, *args):
+        "Save a chart to a pickle file"
+        filename = asksaveasfilename(
+            filetypes=self.CHART_FILE_TYPES, defaultextension=".pickle"
+        )
+        if not filename:
+            return
+        try:
+            with open(filename, "wb") as outfile:
+                pickle.dump(self._chart, outfile)
+        except Exception as e:
+            raise
+            showerror("Error Saving Chart", "Unable to open file: %r" % filename)
+
+    def load_grammar(self, *args):
+        "Load a grammar from a pickle file"
+        filename = askopenfilename(
+            filetypes=self.GRAMMAR_FILE_TYPES, defaultextension=".cfg"
+        )
+        if not filename:
+            return
+        try:
+            if filename.endswith(".pickle"):
+                with open(filename, "rb") as infile:
+                    grammar = pickle.load(infile)
+            else:
+                with open(filename) as infile:
+                    grammar = CFG.fromstring(infile.read())
+            self.set_grammar(grammar)
+        except Exception as e:
+            showerror("Error Loading Grammar", "Unable to open file: %r" % filename)
+
+    def save_grammar(self, *args):
+        filename = asksaveasfilename(
+            filetypes=self.GRAMMAR_FILE_TYPES, defaultextension=".cfg"
+        )
+        if not filename:
+            return
+        try:
+            if filename.endswith(".pickle"):
+                with open(filename, "wb") as outfile:
+                    pickle.dump((self._chart, self._tokens), outfile)
+            else:
+                with open(filename, "w") as outfile:
+                    prods = self._grammar.productions()
+                    start = [p for p in prods if p.lhs() == self._grammar.start()]
+                    rest = [p for p in prods if p.lhs() != self._grammar.start()]
+                    for prod in start:
+                        outfile.write("%s\n" % prod)
+                    for prod in rest:
+                        outfile.write("%s\n" % prod)
+        except Exception as e:
+            showerror("Error Saving Grammar", "Unable to open file: %r" % filename)
+
+    def reset(self, *args):
+        self._animating = 0
+        self._reset_parser()
+        self._cv.update(self._chart)
+        if self._matrix:
+            self._matrix.set_chart(self._chart)
+        if self._matrix:
+            self._matrix.deselect_cell()
+        if self._results:
+            self._results.set_chart(self._chart)
+
+    # ////////////////////////////////////////////////////////////
+    # Edit
+    # ////////////////////////////////////////////////////////////
+
+    def edit_grammar(self, *e):
+        CFGEditor(self._root, self._grammar, self.set_grammar)
+
+    def set_grammar(self, grammar):
+        self._grammar = grammar
+        self._cp.set_grammar(grammar)
+        if self._results:
+            self._results.set_grammar(grammar)
+
+    def edit_sentence(self, *e):
+        sentence = " ".join(self._tokens)
+        title = "Edit Text"
+        instr = "Enter a new sentence to parse."
+        EntryDialog(self._root, sentence, instr, self.set_sentence, title)
+
+    def set_sentence(self, sentence):
+        self._tokens = list(sentence.split())
+        self.reset()
+
+    # ////////////////////////////////////////////////////////////
+    # View Menu
+    # ////////////////////////////////////////////////////////////
+
+    def view_matrix(self, *e):
+        if self._matrix is not None:
+            self._matrix.destroy()
+        self._matrix = ChartMatrixView(self._root, self._chart)
+        self._matrix.add_callback("select", self._select_matrix_edge)
+
+    def view_results(self, *e):
+        if self._results is not None:
+            self._results.destroy()
+        self._results = ChartResultsView(self._root, self._chart, self._grammar)
+
+    # ////////////////////////////////////////////////////////////
+    # Zoom Menu
+    # ////////////////////////////////////////////////////////////
+
+    def resize(self):
+        self._animating = 0
+        self.set_font_size(self._size.get())
+
+    def set_font_size(self, size):
+        self._cv.set_font_size(size)
+        self._font.configure(size=-abs(size))
+        self._boldfont.configure(size=-abs(size))
+        self._sysfont.configure(size=-abs(size))
+
+    def get_font_size(self):
+        return abs(self._size.get())
+
+    # ////////////////////////////////////////////////////////////
+    # Parsing
+    # ////////////////////////////////////////////////////////////
+
+    def apply_strategy(self, strategy, edge_strategy=None):
+        # If we're animating, then stop.
+        if self._animating:
+            self._animating = 0
+            return
+
+        # Clear the rule display & mark.
+        self._display_rule(None)
+        # self._cv.unmark_edge()
+
+        if self._step.get():
+            selection = self._selection
+            if (selection is not None) and (edge_strategy is not None):
+                # Apply the given strategy to the selected edge.
+                self._cp.set_strategy([edge_strategy(selection)])
+                newedge = self._apply_strategy()
+
+                # If it failed, then clear the selection.
+                if newedge is None:
+                    self._cv.unmark_edge()
+                    self._selection = None
+            else:
+                self._cp.set_strategy(strategy)
+                self._apply_strategy()
+
+        else:
+            self._cp.set_strategy(strategy)
+            if self._animate.get():
+                self._animating = 1
+                self._animate_strategy()
+            else:
+                for edge in self._cpstep:
+                    if edge is None:
+                        break
+                self._cv.update()
+                if self._matrix:
+                    self._matrix.update()
+                if self._results:
+                    self._results.update()
+
+    def _stop_animation(self, *e):
+        self._animating = 0
+
+    def _animate_strategy(self, speed=1):
+        if self._animating == 0:
+            return
+        if self._apply_strategy() is not None:
+            if self._animate.get() == 0 or self._step.get() == 1:
+                return
+            if self._animate.get() == 1:
+                self._root.after(3000, self._animate_strategy)
+            elif self._animate.get() == 2:
+                self._root.after(1000, self._animate_strategy)
+            else:
+                self._root.after(20, self._animate_strategy)
+
+    def _apply_strategy(self):
+        new_edge = next(self._cpstep)
+
+        if new_edge is not None:
+            self._show_new_edge(new_edge)
+        return new_edge
+
+    def _display_rule(self, rule):
+        if rule is None:
+            self._rulelabel2["text"] = ""
+        else:
+            name = str(rule)
+            self._rulelabel2["text"] = name
+            size = self._cv.get_font_size()
+
+    # ////////////////////////////////////////////////////////////
+    # Parsing Strategies
+    # ////////////////////////////////////////////////////////////
+
+    # Basic rules:
+    _TD_INIT = [TopDownInitRule()]
+    _TD_PREDICT = [TopDownPredictRule()]
+    _BU_RULE = [BottomUpPredictRule()]
+    _BU_LC_RULE = [BottomUpPredictCombineRule()]
+    _FUNDAMENTAL = [SingleEdgeFundamentalRule()]
+
+    # Complete strategies:
+    _TD_STRATEGY = _TD_INIT + _TD_PREDICT + _FUNDAMENTAL
+    _BU_STRATEGY = _BU_RULE + _FUNDAMENTAL
+    _BU_LC_STRATEGY = _BU_LC_RULE + _FUNDAMENTAL
+
+    # Button callback functions:
+    def top_down_init(self, *e):
+        self.apply_strategy(self._TD_INIT, None)
+
+    def top_down_predict(self, *e):
+        self.apply_strategy(self._TD_PREDICT, TopDownPredictEdgeRule)
+
+    def bottom_up(self, *e):
+        self.apply_strategy(self._BU_RULE, BottomUpEdgeRule)
+
+    def bottom_up_leftcorner(self, *e):
+        self.apply_strategy(self._BU_LC_RULE, BottomUpLeftCornerEdgeRule)
+
+    def fundamental(self, *e):
+        self.apply_strategy(self._FUNDAMENTAL, FundamentalEdgeRule)
+
+    def bottom_up_strategy(self, *e):
+        self.apply_strategy(self._BU_STRATEGY, BottomUpEdgeRule)
+
+    def bottom_up_leftcorner_strategy(self, *e):
+        self.apply_strategy(self._BU_LC_STRATEGY, BottomUpLeftCornerEdgeRule)
+
+    def top_down_strategy(self, *e):
+        self.apply_strategy(self._TD_STRATEGY, TopDownPredictEdgeRule)
+
+
+def app():
+    grammar = CFG.fromstring(
+        """
+    # Grammatical productions.
+        S -> NP VP
+        VP -> VP PP | V NP | V
+        NP -> Det N | NP PP
+        PP -> P NP
+    # Lexical productions.
+        NP -> 'John' | 'I'
+        Det -> 'the' | 'my' | 'a'
+        N -> 'dog' | 'cookie' | 'table' | 'cake' | 'fork'
+        V -> 'ate' | 'saw'
+        P -> 'on' | 'under' | 'with'
+    """
+    )
+
+    sent = "John ate the cake on the table with a fork"
+    sent = "John ate the cake on the table"
+    tokens = list(sent.split())
+
+    print("grammar= (")
+    for rule in grammar.productions():
+        print(("    ", repr(rule) + ","))
+    print(")")
+    print("tokens = %r" % tokens)
+    print('Calling "ChartParserApp(grammar, tokens)"...')
+    ChartParserApp(grammar, tokens).mainloop()
+
+
+if __name__ == "__main__":
+    app()
+
+    # Chart comparer:
+    # charts = ['/tmp/earley.pickle',
+    #          '/tmp/topdown.pickle',
+    #          '/tmp/bottomup.pickle']
+    # ChartComparer(*charts).mainloop()
+
+    # import profile
+    # profile.run('demo2()', '/tmp/profile.out')
+    # import pstats
+    # p = pstats.Stats('/tmp/profile.out')
+    # p.strip_dirs().sort_stats('time', 'cum').print_stats(60)
+    # p.strip_dirs().sort_stats('cum', 'time').print_stats(60)
+
+__all__ = ["app"]

infer_4_37_2/lib/python3.10/site-packages/nltk/app/concordance_app.py

@@ -0,0 +1,709 @@
+# Natural Language Toolkit: Concordance Application
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Sumukh Ghodke <[email protected]>
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+import queue as q
+import re
+import threading
+from tkinter import (
+    END,
+    LEFT,
+    SUNKEN,
+    Button,
+    Entry,
+    Frame,
+    IntVar,
+    Label,
+    Menu,
+    OptionMenu,
+    Scrollbar,
+    StringVar,
+    Text,
+    Tk,
+)
+from tkinter.font import Font
+
+from nltk.corpus import (
+    alpino,
+    brown,
+    cess_cat,
+    cess_esp,
+    floresta,
+    indian,
+    mac_morpho,
+    nps_chat,
+    sinica_treebank,
+    treebank,
+)
+from nltk.draw.util import ShowText
+from nltk.util import in_idle
+
+WORD_OR_TAG = "[^/ ]+"
+BOUNDARY = r"\b"
+
+CORPUS_LOADED_EVENT = "<<CL_EVENT>>"
+SEARCH_TERMINATED_EVENT = "<<ST_EVENT>>"
+SEARCH_ERROR_EVENT = "<<SE_EVENT>>"
+ERROR_LOADING_CORPUS_EVENT = "<<ELC_EVENT>>"
+
+POLL_INTERVAL = 50
+
+# NB All corpora must be specified in a lambda expression so as not to be
+# loaded when the module is imported.
+
+_DEFAULT = "English: Brown Corpus (Humor, simplified)"
+_CORPORA = {
+    "Catalan: CESS-CAT Corpus (simplified)": lambda: cess_cat.tagged_sents(
+        tagset="universal"
+    ),
+    "English: Brown Corpus": lambda: brown.tagged_sents(),
+    "English: Brown Corpus (simplified)": lambda: brown.tagged_sents(
+        tagset="universal"
+    ),
+    "English: Brown Corpus (Press, simplified)": lambda: brown.tagged_sents(
+        categories=["news", "editorial", "reviews"], tagset="universal"
+    ),
+    "English: Brown Corpus (Religion, simplified)": lambda: brown.tagged_sents(
+        categories="religion", tagset="universal"
+    ),
+    "English: Brown Corpus (Learned, simplified)": lambda: brown.tagged_sents(
+        categories="learned", tagset="universal"
+    ),
+    "English: Brown Corpus (Science Fiction, simplified)": lambda: brown.tagged_sents(
+        categories="science_fiction", tagset="universal"
+    ),
+    "English: Brown Corpus (Romance, simplified)": lambda: brown.tagged_sents(
+        categories="romance", tagset="universal"
+    ),
+    "English: Brown Corpus (Humor, simplified)": lambda: brown.tagged_sents(
+        categories="humor", tagset="universal"
+    ),
+    "English: NPS Chat Corpus": lambda: nps_chat.tagged_posts(),
+    "English: NPS Chat Corpus (simplified)": lambda: nps_chat.tagged_posts(
+        tagset="universal"
+    ),
+    "English: Wall Street Journal Corpus": lambda: treebank.tagged_sents(),
+    "English: Wall Street Journal Corpus (simplified)": lambda: treebank.tagged_sents(
+        tagset="universal"
+    ),
+    "Chinese: Sinica Corpus": lambda: sinica_treebank.tagged_sents(),
+    "Chinese: Sinica Corpus (simplified)": lambda: sinica_treebank.tagged_sents(
+        tagset="universal"
+    ),
+    "Dutch: Alpino Corpus": lambda: alpino.tagged_sents(),
+    "Dutch: Alpino Corpus (simplified)": lambda: alpino.tagged_sents(
+        tagset="universal"
+    ),
+    "Hindi: Indian Languages Corpus": lambda: indian.tagged_sents(files="hindi.pos"),
+    "Hindi: Indian Languages Corpus (simplified)": lambda: indian.tagged_sents(
+        files="hindi.pos", tagset="universal"
+    ),
+    "Portuguese: Floresta Corpus (Portugal)": lambda: floresta.tagged_sents(),
+    "Portuguese: Floresta Corpus (Portugal, simplified)": lambda: floresta.tagged_sents(
+        tagset="universal"
+    ),
+    "Portuguese: MAC-MORPHO Corpus (Brazil)": lambda: mac_morpho.tagged_sents(),
+    "Portuguese: MAC-MORPHO Corpus (Brazil, simplified)": lambda: mac_morpho.tagged_sents(
+        tagset="universal"
+    ),
+    "Spanish: CESS-ESP Corpus (simplified)": lambda: cess_esp.tagged_sents(
+        tagset="universal"
+    ),
+}
+
+
+class ConcordanceSearchView:
+    _BACKGROUND_COLOUR = "#FFF"  # white
+
+    # Colour of highlighted results
+    _HIGHLIGHT_WORD_COLOUR = "#F00"  # red
+    _HIGHLIGHT_WORD_TAG = "HL_WRD_TAG"
+
+    _HIGHLIGHT_LABEL_COLOUR = "#C0C0C0"  # dark grey
+    _HIGHLIGHT_LABEL_TAG = "HL_LBL_TAG"
+
+    # Percentage of text left of the scrollbar position
+    _FRACTION_LEFT_TEXT = 0.30
+
+    def __init__(self):
+        self.queue = q.Queue()
+        self.model = ConcordanceSearchModel(self.queue)
+        self.top = Tk()
+        self._init_top(self.top)
+        self._init_menubar()
+        self._init_widgets(self.top)
+        self.load_corpus(self.model.DEFAULT_CORPUS)
+        self.after = self.top.after(POLL_INTERVAL, self._poll)
+
+    def _init_top(self, top):
+        top.geometry("950x680+50+50")
+        top.title("NLTK Concordance Search")
+        top.bind("<Control-q>", self.destroy)
+        top.protocol("WM_DELETE_WINDOW", self.destroy)
+        top.minsize(950, 680)
+
+    def _init_widgets(self, parent):
+        self.main_frame = Frame(
+            parent, dict(background=self._BACKGROUND_COLOUR, padx=1, pady=1, border=1)
+        )
+        self._init_corpus_select(self.main_frame)
+        self._init_query_box(self.main_frame)
+        self._init_results_box(self.main_frame)
+        self._init_paging(self.main_frame)
+        self._init_status(self.main_frame)
+        self.main_frame.pack(fill="both", expand=True)
+
+    def _init_menubar(self):
+        self._result_size = IntVar(self.top)
+        self._cntx_bf_len = IntVar(self.top)
+        self._cntx_af_len = IntVar(self.top)
+        menubar = Menu(self.top)
+
+        filemenu = Menu(menubar, tearoff=0, borderwidth=0)
+        filemenu.add_command(
+            label="Exit", underline=1, command=self.destroy, accelerator="Ctrl-q"
+        )
+        menubar.add_cascade(label="File", underline=0, menu=filemenu)
+
+        editmenu = Menu(menubar, tearoff=0)
+        rescntmenu = Menu(editmenu, tearoff=0)
+        rescntmenu.add_radiobutton(
+            label="20",
+            variable=self._result_size,
+            underline=0,
+            value=20,
+            command=self.set_result_size,
+        )
+        rescntmenu.add_radiobutton(
+            label="50",
+            variable=self._result_size,
+            underline=0,
+            value=50,
+            command=self.set_result_size,
+        )
+        rescntmenu.add_radiobutton(
+            label="100",
+            variable=self._result_size,
+            underline=0,
+            value=100,
+            command=self.set_result_size,
+        )
+        rescntmenu.invoke(1)
+        editmenu.add_cascade(label="Result Count", underline=0, menu=rescntmenu)
+
+        cntxmenu = Menu(editmenu, tearoff=0)
+        cntxbfmenu = Menu(cntxmenu, tearoff=0)
+        cntxbfmenu.add_radiobutton(
+            label="60 characters",
+            variable=self._cntx_bf_len,
+            underline=0,
+            value=60,
+            command=self.set_cntx_bf_len,
+        )
+        cntxbfmenu.add_radiobutton(
+            label="80 characters",
+            variable=self._cntx_bf_len,
+            underline=0,
+            value=80,
+            command=self.set_cntx_bf_len,
+        )
+        cntxbfmenu.add_radiobutton(
+            label="100 characters",
+            variable=self._cntx_bf_len,
+            underline=0,
+            value=100,
+            command=self.set_cntx_bf_len,
+        )
+        cntxbfmenu.invoke(1)
+        cntxmenu.add_cascade(label="Before", underline=0, menu=cntxbfmenu)
+
+        cntxafmenu = Menu(cntxmenu, tearoff=0)
+        cntxafmenu.add_radiobutton(
+            label="70 characters",
+            variable=self._cntx_af_len,
+            underline=0,
+            value=70,
+            command=self.set_cntx_af_len,
+        )
+        cntxafmenu.add_radiobutton(
+            label="90 characters",
+            variable=self._cntx_af_len,
+            underline=0,
+            value=90,
+            command=self.set_cntx_af_len,
+        )
+        cntxafmenu.add_radiobutton(
+            label="110 characters",
+            variable=self._cntx_af_len,
+            underline=0,
+            value=110,
+            command=self.set_cntx_af_len,
+        )
+        cntxafmenu.invoke(1)
+        cntxmenu.add_cascade(label="After", underline=0, menu=cntxafmenu)
+
+        editmenu.add_cascade(label="Context", underline=0, menu=cntxmenu)
+
+        menubar.add_cascade(label="Edit", underline=0, menu=editmenu)
+
+        self.top.config(menu=menubar)
+
+    def set_result_size(self, **kwargs):
+        self.model.result_count = self._result_size.get()
+
+    def set_cntx_af_len(self, **kwargs):
+        self._char_after = self._cntx_af_len.get()
+
+    def set_cntx_bf_len(self, **kwargs):
+        self._char_before = self._cntx_bf_len.get()
+
+    def _init_corpus_select(self, parent):
+        innerframe = Frame(parent, background=self._BACKGROUND_COLOUR)
+        self.var = StringVar(innerframe)
+        self.var.set(self.model.DEFAULT_CORPUS)
+        Label(
+            innerframe,
+            justify=LEFT,
+            text=" Corpus: ",
+            background=self._BACKGROUND_COLOUR,
+            padx=2,
+            pady=1,
+            border=0,
+        ).pack(side="left")
+
+        other_corpora = list(self.model.CORPORA.keys()).remove(
+            self.model.DEFAULT_CORPUS
+        )
+        om = OptionMenu(
+            innerframe,
+            self.var,
+            self.model.DEFAULT_CORPUS,
+            command=self.corpus_selected,
+            *self.model.non_default_corpora()
+        )
+        om["borderwidth"] = 0
+        om["highlightthickness"] = 1
+        om.pack(side="left")
+        innerframe.pack(side="top", fill="x", anchor="n")
+
+    def _init_status(self, parent):
+        self.status = Label(
+            parent,
+            justify=LEFT,
+            relief=SUNKEN,
+            background=self._BACKGROUND_COLOUR,
+            border=0,
+            padx=1,
+            pady=0,
+        )
+        self.status.pack(side="top", anchor="sw")
+
+    def _init_query_box(self, parent):
+        innerframe = Frame(parent, background=self._BACKGROUND_COLOUR)
+        another = Frame(innerframe, background=self._BACKGROUND_COLOUR)
+        self.query_box = Entry(another, width=60)
+        self.query_box.pack(side="left", fill="x", pady=25, anchor="center")
+        self.search_button = Button(
+            another,
+            text="Search",
+            command=self.search,
+            borderwidth=1,
+            highlightthickness=1,
+        )
+        self.search_button.pack(side="left", fill="x", pady=25, anchor="center")
+        self.query_box.bind("<KeyPress-Return>", self.search_enter_keypress_handler)
+        another.pack()
+        innerframe.pack(side="top", fill="x", anchor="n")
+
+    def search_enter_keypress_handler(self, *event):
+        self.search()
+
+    def _init_results_box(self, parent):
+        innerframe = Frame(parent)
+        i1 = Frame(innerframe)
+        i2 = Frame(innerframe)
+        vscrollbar = Scrollbar(i1, borderwidth=1)
+        hscrollbar = Scrollbar(i2, borderwidth=1, orient="horiz")
+        self.results_box = Text(
+            i1,
+            font=Font(family="courier", size="16"),
+            state="disabled",
+            borderwidth=1,
+            yscrollcommand=vscrollbar.set,
+            xscrollcommand=hscrollbar.set,
+            wrap="none",
+            width="40",
+            height="20",
+            exportselection=1,
+        )
+        self.results_box.pack(side="left", fill="both", expand=True)
+        self.results_box.tag_config(
+            self._HIGHLIGHT_WORD_TAG, foreground=self._HIGHLIGHT_WORD_COLOUR
+        )
+        self.results_box.tag_config(
+            self._HIGHLIGHT_LABEL_TAG, foreground=self._HIGHLIGHT_LABEL_COLOUR
+        )
+        vscrollbar.pack(side="left", fill="y", anchor="e")
+        vscrollbar.config(command=self.results_box.yview)
+        hscrollbar.pack(side="left", fill="x", expand=True, anchor="w")
+        hscrollbar.config(command=self.results_box.xview)
+        # there is no other way of avoiding the overlap of scrollbars while using pack layout manager!!!
+        Label(i2, text="   ", background=self._BACKGROUND_COLOUR).pack(
+            side="left", anchor="e"
+        )
+        i1.pack(side="top", fill="both", expand=True, anchor="n")
+        i2.pack(side="bottom", fill="x", anchor="s")
+        innerframe.pack(side="top", fill="both", expand=True)
+
+    def _init_paging(self, parent):
+        innerframe = Frame(parent, background=self._BACKGROUND_COLOUR)
+        self.prev = prev = Button(
+            innerframe,
+            text="Previous",
+            command=self.previous,
+            width="10",
+            borderwidth=1,
+            highlightthickness=1,
+            state="disabled",
+        )
+        prev.pack(side="left", anchor="center")
+        self.next = next = Button(
+            innerframe,
+            text="Next",
+            command=self.__next__,
+            width="10",
+            borderwidth=1,
+            highlightthickness=1,
+            state="disabled",
+        )
+        next.pack(side="right", anchor="center")
+        innerframe.pack(side="top", fill="y")
+        self.current_page = 0
+
+    def previous(self):
+        self.clear_results_box()
+        self.freeze_editable()
+        self.model.prev(self.current_page - 1)
+
+    def __next__(self):
+        self.clear_results_box()
+        self.freeze_editable()
+        self.model.next(self.current_page + 1)
+
+    def about(self, *e):
+        ABOUT = "NLTK Concordance Search Demo\n"
+        TITLE = "About: NLTK Concordance Search Demo"
+        try:
+            from tkinter.messagebox import Message
+
+            Message(message=ABOUT, title=TITLE, parent=self.main_frame).show()
+        except:
+            ShowText(self.top, TITLE, ABOUT)
+
+    def _bind_event_handlers(self):
+        self.top.bind(CORPUS_LOADED_EVENT, self.handle_corpus_loaded)
+        self.top.bind(SEARCH_TERMINATED_EVENT, self.handle_search_terminated)
+        self.top.bind(SEARCH_ERROR_EVENT, self.handle_search_error)
+        self.top.bind(ERROR_LOADING_CORPUS_EVENT, self.handle_error_loading_corpus)
+
+    def _poll(self):
+        try:
+            event = self.queue.get(block=False)
+        except q.Empty:
+            pass
+        else:
+            if event == CORPUS_LOADED_EVENT:
+                self.handle_corpus_loaded(event)
+            elif event == SEARCH_TERMINATED_EVENT:
+                self.handle_search_terminated(event)
+            elif event == SEARCH_ERROR_EVENT:
+                self.handle_search_error(event)
+            elif event == ERROR_LOADING_CORPUS_EVENT:
+                self.handle_error_loading_corpus(event)
+        self.after = self.top.after(POLL_INTERVAL, self._poll)
+
+    def handle_error_loading_corpus(self, event):
+        self.status["text"] = "Error in loading " + self.var.get()
+        self.unfreeze_editable()
+        self.clear_all()
+        self.freeze_editable()
+
+    def handle_corpus_loaded(self, event):
+        self.status["text"] = self.var.get() + " is loaded"
+        self.unfreeze_editable()
+        self.clear_all()
+        self.query_box.focus_set()
+
+    def handle_search_terminated(self, event):
+        # todo: refactor the model such that it is less state sensitive
+        results = self.model.get_results()
+        self.write_results(results)
+        self.status["text"] = ""
+        if len(results) == 0:
+            self.status["text"] = "No results found for " + self.model.query
+        else:
+            self.current_page = self.model.last_requested_page
+        self.unfreeze_editable()
+        self.results_box.xview_moveto(self._FRACTION_LEFT_TEXT)
+
+    def handle_search_error(self, event):
+        self.status["text"] = "Error in query " + self.model.query
+        self.unfreeze_editable()
+
+    def corpus_selected(self, *args):
+        new_selection = self.var.get()
+        self.load_corpus(new_selection)
+
+    def load_corpus(self, selection):
+        if self.model.selected_corpus != selection:
+            self.status["text"] = "Loading " + selection + "..."
+            self.freeze_editable()
+            self.model.load_corpus(selection)
+
+    def search(self):
+        self.current_page = 0
+        self.clear_results_box()
+        self.model.reset_results()
+        query = self.query_box.get()
+        if len(query.strip()) == 0:
+            return
+        self.status["text"] = "Searching for " + query
+        self.freeze_editable()
+        self.model.search(query, self.current_page + 1)
+
+    def write_results(self, results):
+        self.results_box["state"] = "normal"
+        row = 1
+        for each in results:
+            sent, pos1, pos2 = each[0].strip(), each[1], each[2]
+            if len(sent) != 0:
+                if pos1 < self._char_before:
+                    sent, pos1, pos2 = self.pad(sent, pos1, pos2)
+                sentence = sent[pos1 - self._char_before : pos1 + self._char_after]
+                if not row == len(results):
+                    sentence += "\n"
+                self.results_box.insert(str(row) + ".0", sentence)
+                word_markers, label_markers = self.words_and_labels(sent, pos1, pos2)
+                for marker in word_markers:
+                    self.results_box.tag_add(
+                        self._HIGHLIGHT_WORD_TAG,
+                        str(row) + "." + str(marker[0]),
+                        str(row) + "." + str(marker[1]),
+                    )
+                for marker in label_markers:
+                    self.results_box.tag_add(
+                        self._HIGHLIGHT_LABEL_TAG,
+                        str(row) + "." + str(marker[0]),
+                        str(row) + "." + str(marker[1]),
+                    )
+                row += 1
+        self.results_box["state"] = "disabled"
+
+    def words_and_labels(self, sentence, pos1, pos2):
+        search_exp = sentence[pos1:pos2]
+        words, labels = [], []
+        labeled_words = search_exp.split(" ")
+        index = 0
+        for each in labeled_words:
+            if each == "":
+                index += 1
+            else:
+                word, label = each.split("/")
+                words.append(
+                    (self._char_before + index, self._char_before + index + len(word))
+                )
+                index += len(word) + 1
+                labels.append(
+                    (self._char_before + index, self._char_before + index + len(label))
+                )
+                index += len(label)
+            index += 1
+        return words, labels
+
+    def pad(self, sent, hstart, hend):
+        if hstart >= self._char_before:
+            return sent, hstart, hend
+        d = self._char_before - hstart
+        sent = "".join([" "] * d) + sent
+        return sent, hstart + d, hend + d
+
+    def destroy(self, *e):
+        if self.top is None:
+            return
+        self.top.after_cancel(self.after)
+        self.top.destroy()
+        self.top = None
+
+    def clear_all(self):
+        self.query_box.delete(0, END)
+        self.model.reset_query()
+        self.clear_results_box()
+
+    def clear_results_box(self):
+        self.results_box["state"] = "normal"
+        self.results_box.delete("1.0", END)
+        self.results_box["state"] = "disabled"
+
+    def freeze_editable(self):
+        self.query_box["state"] = "disabled"
+        self.search_button["state"] = "disabled"
+        self.prev["state"] = "disabled"
+        self.next["state"] = "disabled"
+
+    def unfreeze_editable(self):
+        self.query_box["state"] = "normal"
+        self.search_button["state"] = "normal"
+        self.set_paging_button_states()
+
+    def set_paging_button_states(self):
+        if self.current_page == 0 or self.current_page == 1:
+            self.prev["state"] = "disabled"
+        else:
+            self.prev["state"] = "normal"
+        if self.model.has_more_pages(self.current_page):
+            self.next["state"] = "normal"
+        else:
+            self.next["state"] = "disabled"
+
+    def fire_event(self, event):
+        # Firing an event so that rendering of widgets happen in the mainloop thread
+        self.top.event_generate(event, when="tail")
+
+    def mainloop(self, *args, **kwargs):
+        if in_idle():
+            return
+        self.top.mainloop(*args, **kwargs)
+
+
+class ConcordanceSearchModel:
+    def __init__(self, queue):
+        self.queue = queue
+        self.CORPORA = _CORPORA
+        self.DEFAULT_CORPUS = _DEFAULT
+        self.selected_corpus = None
+        self.reset_query()
+        self.reset_results()
+        self.result_count = None
+        self.last_sent_searched = 0
+
+    def non_default_corpora(self):
+        copy = []
+        copy.extend(list(self.CORPORA.keys()))
+        copy.remove(self.DEFAULT_CORPUS)
+        copy.sort()
+        return copy
+
+    def load_corpus(self, name):
+        self.selected_corpus = name
+        self.tagged_sents = []
+        runner_thread = self.LoadCorpus(name, self)
+        runner_thread.start()
+
+    def search(self, query, page):
+        self.query = query
+        self.last_requested_page = page
+        self.SearchCorpus(self, page, self.result_count).start()
+
+    def next(self, page):
+        self.last_requested_page = page
+        if len(self.results) < page:
+            self.search(self.query, page)
+        else:
+            self.queue.put(SEARCH_TERMINATED_EVENT)
+
+    def prev(self, page):
+        self.last_requested_page = page
+        self.queue.put(SEARCH_TERMINATED_EVENT)
+
+    def reset_results(self):
+        self.last_sent_searched = 0
+        self.results = []
+        self.last_page = None
+
+    def reset_query(self):
+        self.query = None
+
+    def set_results(self, page, resultset):
+        self.results.insert(page - 1, resultset)
+
+    def get_results(self):
+        return self.results[self.last_requested_page - 1]
+
+    def has_more_pages(self, page):
+        if self.results == [] or self.results[0] == []:
+            return False
+        if self.last_page is None:
+            return True
+        return page < self.last_page
+
+    class LoadCorpus(threading.Thread):
+        def __init__(self, name, model):
+            threading.Thread.__init__(self)
+            self.model, self.name = model, name
+
+        def run(self):
+            try:
+                ts = self.model.CORPORA[self.name]()
+                self.model.tagged_sents = [
+                    " ".join(w + "/" + t for (w, t) in sent) for sent in ts
+                ]
+                self.model.queue.put(CORPUS_LOADED_EVENT)
+            except Exception as e:
+                print(e)
+                self.model.queue.put(ERROR_LOADING_CORPUS_EVENT)
+
+    class SearchCorpus(threading.Thread):
+        def __init__(self, model, page, count):
+            self.model, self.count, self.page = model, count, page
+            threading.Thread.__init__(self)
+
+        def run(self):
+            q = self.processed_query()
+            sent_pos, i, sent_count = [], 0, 0
+            for sent in self.model.tagged_sents[self.model.last_sent_searched :]:
+                try:
+                    m = re.search(q, sent)
+                except re.error:
+                    self.model.reset_results()
+                    self.model.queue.put(SEARCH_ERROR_EVENT)
+                    return
+                if m:
+                    sent_pos.append((sent, m.start(), m.end()))
+                    i += 1
+                    if i > self.count:
+                        self.model.last_sent_searched += sent_count - 1
+                        break
+                sent_count += 1
+            if self.count >= len(sent_pos):
+                self.model.last_sent_searched += sent_count - 1
+                self.model.last_page = self.page
+                self.model.set_results(self.page, sent_pos)
+            else:
+                self.model.set_results(self.page, sent_pos[:-1])
+            self.model.queue.put(SEARCH_TERMINATED_EVENT)
+
+        def processed_query(self):
+            new = []
+            for term in self.model.query.split():
+                term = re.sub(r"\.", r"[^/ ]", term)
+                if re.match("[A-Z]+$", term):
+                    new.append(BOUNDARY + WORD_OR_TAG + "/" + term + BOUNDARY)
+                elif "/" in term:
+                    new.append(BOUNDARY + term + BOUNDARY)
+                else:
+                    new.append(BOUNDARY + term + "/" + WORD_OR_TAG + BOUNDARY)
+            return " ".join(new)
+
+
+def app():
+    d = ConcordanceSearchView()
+    d.mainloop()
+
+
+if __name__ == "__main__":
+    app()
+
+__all__ = ["app"]

infer_4_37_2/lib/python3.10/site-packages/nltk/app/nemo_app.py

@@ -0,0 +1,163 @@
+# Finding (and Replacing) Nemo, Version 1.1, Aristide Grange 2006/06/06
+# https://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/496783
+
+"""
+Finding (and Replacing) Nemo
+
+Instant Regular Expressions
+Created by Aristide Grange
+"""
+import itertools
+import re
+from tkinter import SEL_FIRST, SEL_LAST, Frame, Label, PhotoImage, Scrollbar, Text, Tk
+
+windowTitle = "Finding (and Replacing) Nemo"
+initialFind = r"n(.*?)e(.*?)m(.*?)o"
+initialRepl = r"M\1A\2K\3I"
+initialText = """\
+Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
+Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur.
+Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+"""
+images = {
+    "FIND": "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",
+    "find": "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",
+    "REPL": "R0lGODlhMAAjAPcAMf/////3//+lOf+UKf+MEPf///f39/f35/fv7/ecQvecOfecKfeUIfeUGPeUEPeUCPeMAO/37+/v9+/v3u/n3u/n1u+9jO+9c++1hO+ta++tY++tWu+tUu+tSu+lUu+lQu+lMe+UMe+UKe+UGO+UEO+UAO+MCOfv5+fvxufn7+fn5+fnzue9lOe9c+e1jOe1e+e1c+e1a+etWuetUuelQuecOeeUUueUCN7e597e3t7e1t7ezt7evd7Wzt7Oxt7Ovd7Otd7Opd7OnN7Gtd7Gpd69lN61hN6ta96lStbextberdbW3tbWztbWxtbOvdbOrda1hNalUtaECM7W1s7Ozs7Oxs7Otc7Gxs7Gvc69tc69rc69pc61jM6lc8bWlMbOvcbGxsbGpca9tca9pca1nMaMAL3OhL3Gtb21vb21tb2tpb2tnL2tlLW9tbW9pbW9e7W1pbWtjLWcKa21nK2tra2tnK2tlK2lpa2llK2ljK2le6WlnKWljKWUe6WUc6WUY5y1QpyclJycjJychJyUc5yMY5StY5SUe5SMhJSMe5SMc5SMWpSEa5SESoyUe4yMhIyEY4SlKYScWoSMe4SEe4SEa4R7c4R7Y3uMY3uEe3t7e3t7c3tza3tzY3trKXtjIXOcAHOUMXOEY3Nzc3NzWnNrSmulCGuUMWuMGGtzWmtrY2taMWtaGGOUOWOMAGNzUmNjWmNjSmNaUmNaQmNaOWNaIWNSCFqcAFpjUlpSMVpSIVpSEFpKKVKMAFJSUlJSSlJSMVJKMVJKGFJKAFI5CEqUAEqEAEpzQkpKIUpCQkpCGEpCAEo5EEoxAEJjOUJCOUJCAEI5IUIxADl7ADlaITlCOTkxMTkxKTkxEDkhADFzADFrGDE5OTExADEpEClrCCkxKSkpKSkpISkpACkhCCkhACkYACFzACFrACEhCCEYGBhjEBhjABghABgYCBgYABgQEBgQABAQABAIAAhjAAhSAAhKAAgIEAgICABaAABCAAAhAAAQAAAIAAAAAAAAACH+AS4ALAAAAAAwACMAAAj/AAEIHEiwoMGDCBMqXMiwocOHAA4cgEixIIIJO3JMmAjADIqKFU/8MHIkg5EgYXx4iaTkI0iHE6wE2TCggYILQayEAgXIy8uGCKz8sDCAQAMRG3iEcXULlJkJPwli3OFjh9UdYYLE6NBhA04UXHoVA2XoTZgfPKBWlOBDphAWOdfMcfMDLloeO3hIMjbWVCQ5Fn6E2UFxgpsgFjYIEBADrZU6luqEEfqjTqpt54z1uuWqTIcgWAk7PECGzIUQDRosDmxlUrVJkwQJkqVuX71v06YZcyUlROAdbnLAJKPFyAYFAhoMwFlnEh0rWkpz8raPHm7dqKKc/KFFkBUrVn1M/ziBcEIeLUEQI8/AYk0i9Be4sqjsrN66c9/OnbobhpR3HkIUoZ0WVnBE0AGLFKKFD0HAFUQe77HQgQI1hRBDEHMcY0899bBzihZuCPILJD8EccEGGzwAQhFaUHHQH82sUkgeNHISDBk8WCCCcsqFUEQWmOyzjz3sUGNNOO5Y48YOEgowAAQhnBScQV00k82V47jzjy9CXZBcjziFoco//4CDiSOyhPMPLkJZkEBqJmRQxA9uZGEQD8Ncmc044/zzDF2IZQBCCDYE8QMZz/iiCSx0neHGI7BIhhhNn+1gxRpokEcQAp7seWU7/PwTyxqG/iCEEVzQmUombnDRxRExzP9nBR2PCKLFD3UJwcMPa/SRqUGNWJmNOVn+M44ukMRB4KGcWDNLVhuUMEIJAlzwA3DJBHMJIXm4sQYhqyxCRQQGLSIsn1qac2UzysQSyzX/hLMGD0F0IMCODYAQBA9W/PKPOcRiw0wzwxTiokF9dLMnuv/Mo+fCZF7jBr0xbDDCACWEYKgb1vzjDp/jZNOMLX0IZxAKq2TZTjtaOjwOsXyG+s8sZJTIQsUdIGHoJPf8w487QI/TDSt5mGwQFZxc406o8HiDJchk/ltLHpSlJwSvz5DpTjvmuGNOM57koelBOaAhiCaaPBLL0wwbm003peRBnBZqJMJL1ECz/HXYYx/NdAIOOVCxQyLorswymU93o0wuwfAiTDNR/xz0MLXU0XdCE+UwSTRZAq2lsSATu+4wkGvt+TjNzPLrQyegAUku2Hij5cd8LhxyM8QIg4w18HgcdC6BTBFSDmfQqsovttveDcG7lFLHI75cE841sARCxeWsnxC4G9HADPK6ywzDCRqBo0EHHWhMgT1IJzziNci1N7PMKnSYfML96/90AiJKey/0KtbLX1QK0rrNnQ541xugQ7SHhkXBghN0SKACWRc4KlAhBwKcIOYymJCAAAA7",
+    "repl": "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",
+}
+colors = ["#FF7B39", "#80F121"]
+emphColors = ["#DAFC33", "#F42548"]
+fieldParams = {
+    "height": 3,
+    "width": 70,
+    "font": ("monaco", 14),
+    "highlightthickness": 0,
+    "borderwidth": 0,
+    "background": "white",
+}
+textParams = {
+    "bg": "#F7E0D4",
+    "fg": "#2321F1",
+    "highlightthickness": 0,
+    "width": 1,
+    "height": 10,
+    "font": ("verdana", 16),
+    "wrap": "word",
+}
+
+
+class Zone:
+    def __init__(self, image, initialField, initialText):
+        frm = Frame(root)
+        frm.config(background="white")
+        self.image = PhotoImage(format="gif", data=images[image.upper()])
+        self.imageDimmed = PhotoImage(format="gif", data=images[image])
+        self.img = Label(frm)
+        self.img.config(borderwidth=0)
+        self.img.pack(side="left")
+        self.fld = Text(frm, **fieldParams)
+        self.initScrollText(frm, self.fld, initialField)
+        frm = Frame(root)
+        self.txt = Text(frm, **textParams)
+        self.initScrollText(frm, self.txt, initialText)
+        for i in range(2):
+            self.txt.tag_config(colors[i], background=colors[i])
+            self.txt.tag_config("emph" + colors[i], foreground=emphColors[i])
+
+    def initScrollText(self, frm, txt, contents):
+        scl = Scrollbar(frm)
+        scl.config(command=txt.yview)
+        scl.pack(side="right", fill="y")
+        txt.pack(side="left", expand=True, fill="x")
+        txt.config(yscrollcommand=scl.set)
+        txt.insert("1.0", contents)
+        frm.pack(fill="x")
+        Frame(height=2, bd=1, relief="ridge").pack(fill="x")
+
+    def refresh(self):
+        self.colorCycle = itertools.cycle(colors)
+        try:
+            self.substitute()
+            self.img.config(image=self.image)
+        except re.error:
+            self.img.config(image=self.imageDimmed)
+
+
+class FindZone(Zone):
+    def addTags(self, m):
+        color = next(self.colorCycle)
+        self.txt.tag_add(color, "1.0+%sc" % m.start(), "1.0+%sc" % m.end())
+        try:
+            self.txt.tag_add(
+                "emph" + color, "1.0+%sc" % m.start("emph"), "1.0+%sc" % m.end("emph")
+            )
+        except:
+            pass
+
+    def substitute(self, *args):
+        for color in colors:
+            self.txt.tag_remove(color, "1.0", "end")
+            self.txt.tag_remove("emph" + color, "1.0", "end")
+        self.rex = re.compile("")  # default value in case of malformed regexp
+        self.rex = re.compile(self.fld.get("1.0", "end")[:-1], re.MULTILINE)
+        try:
+            re.compile("(?P<emph>%s)" % self.fld.get(SEL_FIRST, SEL_LAST))
+            self.rexSel = re.compile(
+                "%s(?P<emph>%s)%s"
+                % (
+                    self.fld.get("1.0", SEL_FIRST),
+                    self.fld.get(SEL_FIRST, SEL_LAST),
+                    self.fld.get(SEL_LAST, "end")[:-1],
+                ),
+                re.MULTILINE,
+            )
+        except:
+            self.rexSel = self.rex
+        self.rexSel.sub(self.addTags, self.txt.get("1.0", "end"))
+
+
+class ReplaceZone(Zone):
+    def addTags(self, m):
+        s = sz.rex.sub(self.repl, m.group())
+        self.txt.delete(
+            "1.0+%sc" % (m.start() + self.diff), "1.0+%sc" % (m.end() + self.diff)
+        )
+        self.txt.insert("1.0+%sc" % (m.start() + self.diff), s, next(self.colorCycle))
+        self.diff += len(s) - (m.end() - m.start())
+
+    def substitute(self):
+        self.txt.delete("1.0", "end")
+        self.txt.insert("1.0", sz.txt.get("1.0", "end")[:-1])
+        self.diff = 0
+        self.repl = rex0.sub(r"\\g<\1>", self.fld.get("1.0", "end")[:-1])
+        sz.rex.sub(self.addTags, sz.txt.get("1.0", "end")[:-1])
+
+
+def launchRefresh(_):
+    sz.fld.after_idle(sz.refresh)
+    rz.fld.after_idle(rz.refresh)
+
+
+def app():
+    global root, sz, rz, rex0
+    root = Tk()
+    root.resizable(height=False, width=True)
+    root.title(windowTitle)
+    root.minsize(width=250, height=0)
+    sz = FindZone("find", initialFind, initialText)
+    sz.fld.bind("<Button-1>", launchRefresh)
+    sz.fld.bind("<ButtonRelease-1>", launchRefresh)
+    sz.fld.bind("<B1-Motion>", launchRefresh)
+    sz.rexSel = re.compile("")
+    rz = ReplaceZone("repl", initialRepl, "")
+    rex0 = re.compile(r"(?<!\\)\\([0-9]+)")
+    root.bind_all("<Key>", launchRefresh)
+    launchRefresh(None)
+    root.mainloop()
+
+
+if __name__ == "__main__":
+    app()
+
+__all__ = ["app"]

infer_4_37_2/lib/python3.10/site-packages/nltk/app/rdparser_app.py

@@ -0,0 +1,1052 @@
+# Natural Language Toolkit: Recursive Descent Parser Application
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Edward Loper <[email protected]>
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+A graphical tool for exploring the recursive descent parser.
+
+The recursive descent parser maintains a tree, which records the
+structure of the portion of the text that has been parsed.  It uses
+CFG productions to expand the fringe of the tree, and matches its
+leaves against the text.  Initially, the tree contains the start
+symbol ("S").  It is shown in the main canvas, to the right of the
+list of available expansions.
+
+The parser builds up a tree structure for the text using three
+operations:
+
+  - "expand" uses a CFG production to add children to a node on the
+    fringe of the tree.
+  - "match" compares a leaf in the tree to a text token.
+  - "backtrack" returns the tree to its state before the most recent
+    expand or match operation.
+
+The parser maintains a list of tree locations called a "frontier" to
+remember which nodes have not yet been expanded and which leaves have
+not yet been matched against the text.  The leftmost frontier node is
+shown in green, and the other frontier nodes are shown in blue.  The
+parser always performs expand and match operations on the leftmost
+element of the frontier.
+
+You can control the parser's operation by using the "expand," "match,"
+and "backtrack" 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:
+
+  - If the leftmost frontier element is a token, try matching it.
+  - If the leftmost frontier element is a node, try expanding it with
+    the first untried expansion.
+  - Otherwise, backtrack.
+
+The "expand" button applies the untried expansion whose CFG production
+is listed earliest in the grammar.  To manually choose which expansion
+to apply, click on a CFG production from the list of available
+expansions, on the left side of the main window.
+
+The "autostep" button will let the parser continue applying
+applications to the tree until it reaches a complete parse.  You can
+cancel an autostep in progress at any time by clicking on the
+"autostep" button again.
+
+Keyboard Shortcuts::
+      [Space]\t Perform the next expand, match, or backtrack operation
+      [a]\t Step through operations until the next complete parse
+      [e]\t Perform an expand operation
+      [m]\t Perform a match operation
+      [b]\t Perform a backtrack operation
+      [Delete]\t Reset the parser
+      [g]\t Show/hide available expansions list
+      [h]\t Help
+      [Ctrl-p]\t Print
+      [q]\t Quit
+"""
+
+from tkinter import Button, Frame, IntVar, Label, Listbox, Menu, Scrollbar, Tk
+from tkinter.font import Font
+
+from nltk.draw import CFGEditor, TreeSegmentWidget, tree_to_treesegment
+from nltk.draw.util import CanvasFrame, EntryDialog, ShowText, TextWidget
+from nltk.parse import SteppingRecursiveDescentParser
+from nltk.tree import Tree
+from nltk.util import in_idle
+
+
+class RecursiveDescentApp:
+    """
+    A graphical tool for exploring the recursive descent parser.  The tool
+    displays the parser's tree and the remaining text, and allows the
+    user to control the parser's operation.  In particular, the user
+    can expand subtrees on the frontier, match tokens on the frontier
+    against the text, and backtrack.  A "step" button simply steps
+    through the parsing process, performing the operations that
+    ``RecursiveDescentParser`` would use.
+    """
+
+    def __init__(self, grammar, sent, trace=0):
+        self._sent = sent
+        self._parser = SteppingRecursiveDescentParser(grammar, trace)
+
+        # Set up the main window.
+        self._top = Tk()
+        self._top.title("Recursive Descent Parser Application")
+
+        # Set up key bindings.
+        self._init_bindings()
+
+        # Initialize the fonts.
+        self._init_fonts(self._top)
+
+        # Animations.  animating_lock is a lock to prevent the demo
+        # from performing new operations while it's animating.
+        self._animation_frames = IntVar(self._top)
+        self._animation_frames.set(5)
+        self._animating_lock = 0
+        self._autostep = 0
+
+        # The user can hide the grammar.
+        self._show_grammar = IntVar(self._top)
+        self._show_grammar.set(1)
+
+        # 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)
+
+        # Initialize the parser.
+        self._parser.initialize(self._sent)
+
+        # Resize callback
+        self._canvas.bind("<Configure>", self._configure)
+
+    #########################################
+    ##  Initialization Helpers
+    #########################################
+
+    def _init_fonts(self, root):
+        # See: <http://www.astro.washington.edu/owen/ROTKFolklore.html>
+        self._sysfont = 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 = Font(family="helvetica", weight="bold", size=self._size.get())
+        self._font = Font(family="helvetica", size=self._size.get())
+        if self._size.get() < 0:
+            big = self._size.get() - 2
+        else:
+            big = self._size.get() + 2
+        self._bigfont = Font(family="helvetica", weight="bold", size=big)
+
+    def _init_grammar(self, parent):
+        # 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 Expansions"
+        )
+        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 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)
+
+    def _init_bindings(self):
+        # Key bindings are a good thing.
+        self._top.bind("<Control-q>", self.destroy)
+        self._top.bind("<Control-x>", self.destroy)
+        self._top.bind("<Escape>", self.destroy)
+        self._top.bind("e", self.expand)
+        # self._top.bind('<Alt-e>', self.expand)
+        # self._top.bind('<Control-e>', self.expand)
+        self._top.bind("m", self.match)
+        self._top.bind("<Alt-m>", self.match)
+        self._top.bind("<Control-m>", self.match)
+        self._top.bind("b", self.backtrack)
+        self._top.bind("<Alt-b>", self.backtrack)
+        self._top.bind("<Control-b>", self.backtrack)
+        self._top.bind("<Control-z>", self.backtrack)
+        self._top.bind("<BackSpace>", self.backtrack)
+        self._top.bind("a", self.autostep)
+        # self._top.bind('<Control-a>', self.autostep)
+        self._top.bind("<Control-space>", self.autostep)
+        self._top.bind("<Control-c>", self.cancel_autostep)
+        self._top.bind("<space>", self.step)
+        self._top.bind("<Delete>", self.reset)
+        self._top.bind("<Control-p>", self.postscript)
+        # self._top.bind('<h>', self.help)
+        # self._top.bind('<Alt-h>', self.help)
+        self._top.bind("<Control-h>", self.help)
+        self._top.bind("<F1>", self.help)
+        # self._top.bind('<g>', self.toggle_grammar)
+        # self._top.bind('<Alt-g>', self.toggle_grammar)
+        # self._top.bind('<Control-g>', self.toggle_grammar)
+        self._top.bind("<Control-g>", self.edit_grammar)
+        self._top.bind("<Control-t>", self.edit_sentence)
+
+    def _init_buttons(self, parent):
+        # Set up the frames.
+        self._buttonframe = buttonframe = Frame(parent)
+        buttonframe.pack(fill="none", side="bottom", padx=3, pady=2)
+        Button(
+            buttonframe,
+            text="Step",
+            background="#90c0d0",
+            foreground="black",
+            command=self.step,
+        ).pack(side="left")
+        Button(
+            buttonframe,
+            text="Autostep",
+            background="#90c0d0",
+            foreground="black",
+            command=self.autostep,
+        ).pack(side="left")
+        Button(
+            buttonframe,
+            text="Expand",
+            underline=0,
+            background="#90f090",
+            foreground="black",
+            command=self.expand,
+        ).pack(side="left")
+        Button(
+            buttonframe,
+            text="Match",
+            underline=0,
+            background="#90f090",
+            foreground="black",
+            command=self.match,
+        ).pack(side="left")
+        Button(
+            buttonframe,
+            text="Backtrack",
+            underline=0,
+            background="#f0a0a0",
+            foreground="black",
+            command=self.backtrack,
+        ).pack(side="left")
+        # Replace autostep...
+
+    #         self._autostep_button = Button(buttonframe, text='Autostep',
+    #                                        underline=0, command=self.autostep)
+    #         self._autostep_button.pack(side='left')
+
+    def _configure(self, event):
+        self._autostep = 0
+        (x1, y1, x2, y2) = self._cframe.scrollregion()
+        y2 = event.height - 6
+        self._canvas["scrollregion"] = "%d %d %d %d" % (x1, y1, x2, y2)
+        self._redraw()
+
+    def _init_feedback(self, parent):
+        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)
+
+    def _init_canvas(self, parent):
+        self._cframe = CanvasFrame(
+            parent,
+            background="white",
+            # width=525, height=250,
+            closeenough=10,
+            border=2,
+            relief="sunken",
+        )
+        self._cframe.pack(expand=1, fill="both", side="top", pady=2)
+        canvas = self._canvas = self._cframe.canvas()
+
+        # Initially, there's no tree or text
+        self._tree = None
+        self._textwidgets = []
+        self._textline = None
+
+    def _init_menubar(self, parent):
+        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="Match", underline=0, command=self.match, accelerator="Ctrl-m"
+        )
+        rulemenu.add_command(
+            label="Expand", underline=0, command=self.expand, accelerator="Ctrl-e"
+        )
+        rulemenu.add_separator()
+        rulemenu.add_command(
+            label="Backtrack", underline=0, command=self.backtrack, accelerator="Ctrl-b"
+        )
+        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._animation_frames, value=0
+        )
+        animatemenu.add_radiobutton(
+            label="Slow Animation",
+            underline=0,
+            variable=self._animation_frames,
+            value=10,
+            accelerator="-",
+        )
+        animatemenu.add_radiobutton(
+            label="Normal Animation",
+            underline=0,
+            variable=self._animation_frames,
+            value=5,
+            accelerator="=",
+        )
+        animatemenu.add_radiobutton(
+            label="Fast Animation",
+            underline=0,
+            variable=self._animation_frames,
+            value=2,
+            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)
+
+    #########################################
+    ##  Helper
+    #########################################
+
+    def _get(self, widget, treeloc):
+        for i in treeloc:
+            widget = widget.subtrees()[i]
+        if isinstance(widget, TreeSegmentWidget):
+            widget = widget.label()
+        return widget
+
+    #########################################
+    ##  Main draw procedure
+    #########################################
+
+    def _redraw(self):
+        canvas = self._canvas
+
+        # Delete the old tree, widgets, etc.
+        if self._tree is not None:
+            self._cframe.destroy_widget(self._tree)
+        for twidget in self._textwidgets:
+            self._cframe.destroy_widget(twidget)
+        if self._textline is not None:
+            self._canvas.delete(self._textline)
+
+        # Draw the tree.
+        helv = ("helvetica", -self._size.get())
+        bold = ("helvetica", -self._size.get(), "bold")
+        attribs = {
+            "tree_color": "#000000",
+            "tree_width": 2,
+            "node_font": bold,
+            "leaf_font": helv,
+        }
+        tree = self._parser.tree()
+        self._tree = tree_to_treesegment(canvas, tree, **attribs)
+        self._cframe.add_widget(self._tree, 30, 5)
+
+        # Draw the text.
+        helv = ("helvetica", -self._size.get())
+        bottom = y = self._cframe.scrollregion()[3]
+        self._textwidgets = [
+            TextWidget(canvas, word, font=self._font) for word in self._sent
+        ]
+        for twidget in self._textwidgets:
+            self._cframe.add_widget(twidget, 0, 0)
+            twidget.move(0, bottom - twidget.bbox()[3] - 5)
+            y = min(y, twidget.bbox()[1])
+
+        # Draw a line over the text, to separate it from the tree.
+        self._textline = canvas.create_line(-5000, y - 5, 5000, y - 5, dash=".")
+
+        # Highlight appropriate nodes.
+        self._highlight_nodes()
+        self._highlight_prodlist()
+
+        # Make sure the text lines up.
+        self._position_text()
+
+    def _redraw_quick(self):
+        # This should be more-or-less sufficient after an animation.
+        self._highlight_nodes()
+        self._highlight_prodlist()
+        self._position_text()
+
+    def _highlight_nodes(self):
+        # Highlight the list of nodes to be checked.
+        bold = ("helvetica", -self._size.get(), "bold")
+        for treeloc in self._parser.frontier()[:1]:
+            self._get(self._tree, treeloc)["color"] = "#20a050"
+            self._get(self._tree, treeloc)["font"] = bold
+        for treeloc in self._parser.frontier()[1:]:
+            self._get(self._tree, treeloc)["color"] = "#008080"
+
+    def _highlight_prodlist(self):
+        # Highlight the productions that can be expanded.
+        # Boy, too bad tkinter doesn't implement Listbox.itemconfig;
+        # that would be pretty useful here.
+        self._prodlist.delete(0, "end")
+        expandable = self._parser.expandable_productions()
+        untried = self._parser.untried_expandable_productions()
+        productions = self._productions
+        for index in range(len(productions)):
+            if productions[index] in expandable:
+                if productions[index] in untried:
+                    self._prodlist.insert(index, " %s" % productions[index])
+                else:
+                    self._prodlist.insert(index, " %s (TRIED)" % productions[index])
+                self._prodlist.selection_set(index)
+            else:
+                self._prodlist.insert(index, " %s" % productions[index])
+
+    def _position_text(self):
+        # Line up the text widgets that are matched against the tree
+        numwords = len(self._sent)
+        num_matched = numwords - len(self._parser.remaining_text())
+        leaves = self._tree_leaves()[:num_matched]
+        xmax = self._tree.bbox()[0]
+        for i in range(0, len(leaves)):
+            widget = self._textwidgets[i]
+            leaf = leaves[i]
+            widget["color"] = "#006040"
+            leaf["color"] = "#006040"
+            widget.move(leaf.bbox()[0] - widget.bbox()[0], 0)
+            xmax = widget.bbox()[2] + 10
+
+        # Line up the text widgets that are not matched against the tree.
+        for i in range(len(leaves), numwords):
+            widget = self._textwidgets[i]
+            widget["color"] = "#a0a0a0"
+            widget.move(xmax - widget.bbox()[0], 0)
+            xmax = widget.bbox()[2] + 10
+
+        # If we have a complete parse, make everything green :)
+        if self._parser.currently_complete():
+            for twidget in self._textwidgets:
+                twidget["color"] = "#00a000"
+
+        # Move the matched leaves down to the text.
+        for i in range(0, len(leaves)):
+            widget = self._textwidgets[i]
+            leaf = leaves[i]
+            dy = widget.bbox()[1] - leaf.bbox()[3] - 10.0
+            dy = max(dy, leaf.parent().label().bbox()[3] - leaf.bbox()[3] + 10)
+            leaf.move(0, dy)
+
+    def _tree_leaves(self, tree=None):
+        if tree is None:
+            tree = self._tree
+        if isinstance(tree, TreeSegmentWidget):
+            leaves = []
+            for child in tree.subtrees():
+                leaves += self._tree_leaves(child)
+            return leaves
+        else:
+            return [tree]
+
+    #########################################
+    ##  Button Callbacks
+    #########################################
+
+    def destroy(self, *e):
+        self._autostep = 0
+        if self._top is None:
+            return
+        self._top.destroy()
+        self._top = None
+
+    def reset(self, *e):
+        self._autostep = 0
+        self._parser.initialize(self._sent)
+        self._lastoper1["text"] = "Reset Application"
+        self._lastoper2["text"] = ""
+        self._redraw()
+
+    def autostep(self, *e):
+        if self._animation_frames.get() == 0:
+            self._animation_frames.set(2)
+        if self._autostep:
+            self._autostep = 0
+        else:
+            self._autostep = 1
+            self._step()
+
+    def cancel_autostep(self, *e):
+        # self._autostep_button['text'] = 'Autostep'
+        self._autostep = 0
+
+    # Make sure to stop auto-stepping if we get any user input.
+    def step(self, *e):
+        self._autostep = 0
+        self._step()
+
+    def match(self, *e):
+        self._autostep = 0
+        self._match()
+
+    def expand(self, *e):
+        self._autostep = 0
+        self._expand()
+
+    def backtrack(self, *e):
+        self._autostep = 0
+        self._backtrack()
+
+    def _step(self):
+        if self._animating_lock:
+            return
+
+        # Try expanding, matching, and backtracking (in that order)
+        if self._expand():
+            pass
+        elif self._parser.untried_match() and self._match():
+            pass
+        elif self._backtrack():
+            pass
+        else:
+            self._lastoper1["text"] = "Finished"
+            self._lastoper2["text"] = ""
+            self._autostep = 0
+
+        # Check if we just completed a parse.
+        if self._parser.currently_complete():
+            self._autostep = 0
+            self._lastoper2["text"] += "    [COMPLETE PARSE]"
+
+    def _expand(self, *e):
+        if self._animating_lock:
+            return
+        old_frontier = self._parser.frontier()
+        rv = self._parser.expand()
+        if rv is not None:
+            self._lastoper1["text"] = "Expand:"
+            self._lastoper2["text"] = rv
+            self._prodlist.selection_clear(0, "end")
+            index = self._productions.index(rv)
+            self._prodlist.selection_set(index)
+            self._animate_expand(old_frontier[0])
+            return True
+        else:
+            self._lastoper1["text"] = "Expand:"
+            self._lastoper2["text"] = "(all expansions tried)"
+            return False
+
+    def _match(self, *e):
+        if self._animating_lock:
+            return
+        old_frontier = self._parser.frontier()
+        rv = self._parser.match()
+        if rv is not None:
+            self._lastoper1["text"] = "Match:"
+            self._lastoper2["text"] = rv
+            self._animate_match(old_frontier[0])
+            return True
+        else:
+            self._lastoper1["text"] = "Match:"
+            self._lastoper2["text"] = "(failed)"
+            return False
+
+    def _backtrack(self, *e):
+        if self._animating_lock:
+            return
+        if self._parser.backtrack():
+            elt = self._parser.tree()
+            for i in self._parser.frontier()[0]:
+                elt = elt[i]
+            self._lastoper1["text"] = "Backtrack"
+            self._lastoper2["text"] = ""
+            if isinstance(elt, Tree):
+                self._animate_backtrack(self._parser.frontier()[0])
+            else:
+                self._animate_match_backtrack(self._parser.frontier()[0])
+            return True
+        else:
+            self._autostep = 0
+            self._lastoper1["text"] = "Finished"
+            self._lastoper2["text"] = ""
+            return False
+
+    def about(self, *e):
+        ABOUT = (
+            "NLTK Recursive Descent Parser Application\n" + "Written by Edward Loper"
+        )
+        TITLE = "About: Recursive Descent Parser Application"
+        try:
+            from tkinter.messagebox import Message
+
+            Message(message=ABOUT, title=TITLE).show()
+        except:
+            ShowText(self._top, TITLE, ABOUT)
+
+    def help(self, *e):
+        self._autostep = 0
+        # The default font's not very legible; try using 'fixed' instead.
+        try:
+            ShowText(
+                self._top,
+                "Help: Recursive Descent Parser Application",
+                (__doc__ or "").strip(),
+                width=75,
+                font="fixed",
+            )
+        except:
+            ShowText(
+                self._top,
+                "Help: Recursive Descent Parser Application",
+                (__doc__ or "").strip(),
+                width=75,
+            )
+
+    def postscript(self, *e):
+        self._autostep = 0
+        self._cframe.print_to_file()
+
+    def mainloop(self, *args, **kwargs):
+        """
+        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)
+
+    def resize(self, size=None):
+        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._bigfont.configure(size=-(abs(size + 2)))
+        self._redraw()
+
+    #########################################
+    ##  Expand Production Selection
+    #########################################
+
+    def _toggle_grammar(self, *e):
+        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"] = ""
+
+    #     def toggle_grammar(self, *e):
+    #         self._show_grammar = not self._show_grammar
+    #         if self._show_grammar:
+    #             self._prodframe.pack(fill='both', expand='y', side='left',
+    #                                  after=self._feedbackframe)
+    #             self._lastoper1['text'] = 'Show Grammar'
+    #         else:
+    #             self._prodframe.pack_forget()
+    #             self._lastoper1['text'] = 'Hide Grammar'
+    #         self._lastoper2['text'] = ''
+
+    def _prodlist_select(self, event):
+        selection = self._prodlist.curselection()
+        if len(selection) != 1:
+            return
+        index = int(selection[0])
+        old_frontier = self._parser.frontier()
+        production = self._parser.expand(self._productions[index])
+
+        if production:
+            self._lastoper1["text"] = "Expand:"
+            self._lastoper2["text"] = production
+            self._prodlist.selection_clear(0, "end")
+            self._prodlist.selection_set(index)
+            self._animate_expand(old_frontier[0])
+        else:
+            # Reset the production selections.
+            self._prodlist.selection_clear(0, "end")
+            for prod in self._parser.expandable_productions():
+                index = self._productions.index(prod)
+                self._prodlist.selection_set(index)
+
+    #########################################
+    ##  Animation
+    #########################################
+
+    def _animate_expand(self, treeloc):
+        oldwidget = self._get(self._tree, treeloc)
+        oldtree = oldwidget.parent()
+        top = not isinstance(oldtree.parent(), TreeSegmentWidget)
+
+        tree = self._parser.tree()
+        for i in treeloc:
+            tree = tree[i]
+
+        widget = tree_to_treesegment(
+            self._canvas,
+            tree,
+            node_font=self._boldfont,
+            leaf_color="white",
+            tree_width=2,
+            tree_color="white",
+            node_color="white",
+            leaf_font=self._font,
+        )
+        widget.label()["color"] = "#20a050"
+
+        (oldx, oldy) = oldtree.label().bbox()[:2]
+        (newx, newy) = widget.label().bbox()[:2]
+        widget.move(oldx - newx, oldy - newy)
+
+        if top:
+            self._cframe.add_widget(widget, 0, 5)
+            widget.move(30 - widget.label().bbox()[0], 0)
+            self._tree = widget
+        else:
+            oldtree.parent().replace_child(oldtree, widget)
+
+        # Move the children over so they don't overlap.
+        # Line the children up in a strange way.
+        if widget.subtrees():
+            dx = (
+                oldx
+                + widget.label().width() / 2
+                - widget.subtrees()[0].bbox()[0] / 2
+                - widget.subtrees()[0].bbox()[2] / 2
+            )
+            for subtree in widget.subtrees():
+                subtree.move(dx, 0)
+
+        self._makeroom(widget)
+
+        if top:
+            self._cframe.destroy_widget(oldtree)
+        else:
+            oldtree.destroy()
+
+        colors = [
+            "gray%d" % (10 * int(10 * x / self._animation_frames.get()))
+            for x in range(self._animation_frames.get(), 0, -1)
+        ]
+
+        # Move the text string down, if necessary.
+        dy = widget.bbox()[3] + 30 - self._canvas.coords(self._textline)[1]
+        if dy > 0:
+            for twidget in self._textwidgets:
+                twidget.move(0, dy)
+            self._canvas.move(self._textline, 0, dy)
+
+        self._animate_expand_frame(widget, colors)
+
+    def _makeroom(self, treeseg):
+        """
+        Make sure that no sibling tree bbox's overlap.
+        """
+        parent = treeseg.parent()
+        if not isinstance(parent, TreeSegmentWidget):
+            return
+
+        index = parent.subtrees().index(treeseg)
+
+        # Handle siblings to the right
+        rsiblings = parent.subtrees()[index + 1 :]
+        if rsiblings:
+            dx = treeseg.bbox()[2] - rsiblings[0].bbox()[0] + 10
+            for sibling in rsiblings:
+                sibling.move(dx, 0)
+
+        # Handle siblings to the left
+        if index > 0:
+            lsibling = parent.subtrees()[index - 1]
+            dx = max(0, lsibling.bbox()[2] - treeseg.bbox()[0] + 10)
+            treeseg.move(dx, 0)
+
+        # Keep working up the tree.
+        self._makeroom(parent)
+
+    def _animate_expand_frame(self, widget, colors):
+        if len(colors) > 0:
+            self._animating_lock = 1
+            widget["color"] = colors[0]
+            for subtree in widget.subtrees():
+                if isinstance(subtree, TreeSegmentWidget):
+                    subtree.label()["color"] = colors[0]
+                else:
+                    subtree["color"] = colors[0]
+            self._top.after(50, self._animate_expand_frame, widget, colors[1:])
+        else:
+            widget["color"] = "black"
+            for subtree in widget.subtrees():
+                if isinstance(subtree, TreeSegmentWidget):
+                    subtree.label()["color"] = "black"
+                else:
+                    subtree["color"] = "black"
+            self._redraw_quick()
+            widget.label()["color"] = "black"
+            self._animating_lock = 0
+            if self._autostep:
+                self._step()
+
+    def _animate_backtrack(self, treeloc):
+        # Flash red first, if we're animating.
+        if self._animation_frames.get() == 0:
+            colors = []
+        else:
+            colors = ["#a00000", "#000000", "#a00000"]
+        colors += [
+            "gray%d" % (10 * int(10 * x / (self._animation_frames.get())))
+            for x in range(1, self._animation_frames.get() + 1)
+        ]
+
+        widgets = [self._get(self._tree, treeloc).parent()]
+        for subtree in widgets[0].subtrees():
+            if isinstance(subtree, TreeSegmentWidget):
+                widgets.append(subtree.label())
+            else:
+                widgets.append(subtree)
+
+        self._animate_backtrack_frame(widgets, colors)
+
+    def _animate_backtrack_frame(self, widgets, colors):
+        if len(colors) > 0:
+            self._animating_lock = 1
+            for widget in widgets:
+                widget["color"] = colors[0]
+            self._top.after(50, self._animate_backtrack_frame, widgets, colors[1:])
+        else:
+            for widget in widgets[0].subtrees():
+                widgets[0].remove_child(widget)
+                widget.destroy()
+            self._redraw_quick()
+            self._animating_lock = 0
+            if self._autostep:
+                self._step()
+
+    def _animate_match_backtrack(self, treeloc):
+        widget = self._get(self._tree, treeloc)
+        node = widget.parent().label()
+        dy = (node.bbox()[3] - widget.bbox()[1] + 14) / max(
+            1, self._animation_frames.get()
+        )
+        self._animate_match_backtrack_frame(self._animation_frames.get(), widget, dy)
+
+    def _animate_match(self, treeloc):
+        widget = self._get(self._tree, treeloc)
+
+        dy = (self._textwidgets[0].bbox()[1] - widget.bbox()[3] - 10.0) / max(
+            1, self._animation_frames.get()
+        )
+        self._animate_match_frame(self._animation_frames.get(), widget, dy)
+
+    def _animate_match_frame(self, frame, widget, dy):
+        if frame > 0:
+            self._animating_lock = 1
+            widget.move(0, dy)
+            self._top.after(10, self._animate_match_frame, frame - 1, widget, dy)
+        else:
+            widget["color"] = "#006040"
+            self._redraw_quick()
+            self._animating_lock = 0
+            if self._autostep:
+                self._step()
+
+    def _animate_match_backtrack_frame(self, frame, widget, dy):
+        if frame > 0:
+            self._animating_lock = 1
+            widget.move(0, dy)
+            self._top.after(
+                10, self._animate_match_backtrack_frame, frame - 1, widget, dy
+            )
+        else:
+            widget.parent().remove_child(widget)
+            widget.destroy()
+            self._animating_lock = 0
+            if self._autostep:
+                self._step()
+
+    def edit_grammar(self, *e):
+        CFGEditor(self._top, self._parser.grammar(), self.set_grammar)
+
+    def set_grammar(self, 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))
+
+    def edit_sentence(self, *e):
+        sentence = " ".join(self._sent)
+        title = "Edit Text"
+        instr = "Enter a new sentence to parse."
+        EntryDialog(self._top, sentence, instr, self.set_sentence, title)
+
+    def set_sentence(self, sentence):
+        self._sent = sentence.split()  # [XX] use tagged?
+        self.reset()
+
+
+def app():
+    """
+    Create a recursive descent parser demo, using a simple grammar and
+    text.
+    """
+    from nltk.grammar import CFG
+
+    grammar = CFG.fromstring(
+        """
+    # Grammatical productions.
+        S -> NP VP
+        NP -> Det N PP | Det N
+        VP -> V NP PP | V NP | V
+        PP -> P NP
+    # Lexical productions.
+        NP -> 'I'
+        Det -> 'the' | 'a'
+        N -> 'man' | 'park' | 'dog' | 'telescope'
+        V -> 'ate' | 'saw'
+        P -> 'in' | 'under' | 'with'
+    """
+    )
+
+    sent = "the dog saw a man in the park".split()
+
+    RecursiveDescentApp(grammar, sent).mainloop()
+
+
+if __name__ == "__main__":
+    app()
+
+__all__ = ["app"]

infer_4_37_2/lib/python3.10/site-packages/nltk/app/srparser_app.py

@@ -0,0 +1,937 @@
+# Natural Language Toolkit: Shift-Reduce Parser Application
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Edward Loper <[email protected]>
+# URL: <https://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
+
+"""
+
+from tkinter import Button, Frame, IntVar, Label, Listbox, Menu, Scrollbar, Tk
+from tkinter.font import Font
+
+from nltk.draw import CFGEditor, TreeSegmentWidget, tree_to_treesegment
+from nltk.draw.util import CanvasFrame, EntryDialog, ShowText, TextWidget
+from nltk.parse import SteppingShiftReduceParser
+from nltk.tree import Tree
+from nltk.util import in_idle
+
+"""
+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.
+"""
+
+
+class ShiftReduceApp:
+    """
+    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.
+    """
+
+    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"] = ""
+
+    #########################################
+    ##  Initialization Helpers
+    #########################################
+
+    def _init_fonts(self, root):
+        # See: <http://www.astro.washington.edu/owen/ROTKFolklore.html>
+        self._sysfont = 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 = Font(family="helvetica", weight="bold", size=self._size.get())
+        self._font = Font(family="helvetica", size=self._size.get())
+
+    def _init_grammar(self, parent):
+        # 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)
+
+    def _init_bindings(self):
+        # 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))
+
+    def _init_buttons(self, parent):
+        # 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")
+
+    def _init_menubar(self, parent):
+        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)
+
+    def _init_feedback(self, parent):
+        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)
+
+    def _init_canvas(self, parent):
+        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
+    #########################################
+
+    def _redraw(self):
+        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.label()["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()
+
+    def _draw_stack_top(self, widget):
+        # hack..
+        midx = widget.bbox()[2] + 50
+        self._canvas.coords(self._stacktop, midx, 0, midx, 5000)
+
+    def _highlight_productions(self):
+        # 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
+    #########################################
+
+    def destroy(self, *e):
+        if self._top is None:
+            return
+        self._top.destroy()
+        self._top = None
+
+    def reset(self, *e):
+        self._parser.initialize(self._sent)
+        self._lastoper1["text"] = "Reset App"
+        self._lastoper2["text"] = ""
+        self._redraw()
+
+    def step(self, *e):
+        if self.reduce():
+            return True
+        elif self.shift():
+            return True
+        else:
+            if list(self._parser.parses()):
+                self._lastoper1["text"] = "Finished:"
+                self._lastoper2["text"] = "Success"
+            else:
+                self._lastoper1["text"] = "Finished:"
+                self._lastoper2["text"] = "Failure"
+
+    def shift(self, *e):
+        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 True
+        return False
+
+    def reduce(self, *e):
+        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
+
+    def undo(self, *e):
+        if self._animating_lock:
+            return
+        if self._parser.undo():
+            self._redraw()
+
+    def postscript(self, *e):
+        self._cframe.print_to_file()
+
+    def mainloop(self, *args, **kwargs):
+        """
+        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
+    #########################################
+
+    def resize(self, size=None):
+        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()
+
+    def help(self, *e):
+        # The default font's not very legible; try using 'fixed' instead.
+        try:
+            ShowText(
+                self._top,
+                "Help: Shift-Reduce Parser Application",
+                (__doc__ or "").strip(),
+                width=75,
+                font="fixed",
+            )
+        except:
+            ShowText(
+                self._top,
+                "Help: Shift-Reduce Parser Application",
+                (__doc__ or "").strip(),
+                width=75,
+            )
+
+    def about(self, *e):
+        ABOUT = "NLTK Shift-Reduce Parser Application\n" + "Written by Edward Loper"
+        TITLE = "About: Shift-Reduce Parser Application"
+        try:
+            from tkinter.messagebox import Message
+
+            Message(message=ABOUT, title=TITLE).show()
+        except:
+            ShowText(self._top, TITLE, ABOUT)
+
+    def edit_grammar(self, *e):
+        CFGEditor(self._top, self._parser.grammar(), self.set_grammar)
+
+    def set_grammar(self, 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))
+
+    def edit_sentence(self, *e):
+        sentence = " ".join(self._sent)
+        title = "Edit Text"
+        instr = "Enter a new sentence to parse."
+        EntryDialog(self._top, sentence, instr, self.set_sentence, title)
+
+    def set_sentence(self, sent):
+        self._sent = sent.split()  # [XX] use tagged?
+        self.reset()
+
+    #########################################
+    ##  Reduce Production Selection
+    #########################################
+
+    def _toggle_grammar(self, *e):
+        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"] = ""
+
+    def _prodlist_select(self, event):
+        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)
+
+    def _popup_reduce(self, widget):
+        # 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
+    #########################################
+
+    def _animate_shift(self):
+        # 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)
+
+    def _animate_shift_frame(self, frame, 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()
+
+    def _animate_reduce(self):
+        # 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].label().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)
+
+    def _animate_reduce_frame(self, frame, 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.label()), 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.
+    #########################################
+
+    def _highlight_hover(self, event):
+        # 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.label()["color"] = "#00a000"
+                else:
+                    stackwidget["color"] = "#00a000"
+
+        # Remember what production we're hovering over.
+        self._hover = index
+
+    def _clear_hover(self, *event):
+        # Clear any previous hover highlighting.
+        if self._hover == -1:
+            return
+        self._hover = -1
+        for stackwidget in self._stackwidgets:
+            if isinstance(stackwidget, TreeSegmentWidget):
+                stackwidget.label()["color"] = "black"
+            else:
+                stackwidget["color"] = "black"
+
+
+def app():
+    """
+    Create a shift reduce parser app, using a simple grammar and
+    text.
+    """
+
+    from nltk.grammar import CFG, Nonterminal, Production
+
+    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 = CFG(S, productions)
+
+    # tokenize the sentence
+    sent = "my dog saw a man in the park with a statue".split()
+
+    ShiftReduceApp(grammar, sent).mainloop()
+
+
+if __name__ == "__main__":
+    app()
+
+__all__ = ["app"]

infer_4_37_2/lib/python3.10/site-packages/nltk/app/wordnet_app.py

@@ -0,0 +1,1006 @@
+# Natural Language Toolkit: WordNet Browser Application
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Jussi Salmela <[email protected]>
+#         Paul Bone <[email protected]>
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+A WordNet Browser application which launches the default browser
+(if it is not already running) and opens a new tab with a connection
+to http://localhost:port/ .  It also starts an HTTP server on the
+specified port and begins serving browser requests.  The default
+port is 8000.  (For command-line help, run "python wordnet -h")
+This application requires that the user's web browser supports
+Javascript.
+
+BrowServer is a server for browsing the NLTK Wordnet database It first
+launches a browser client to be used for browsing and then starts
+serving the requests of that and maybe other clients
+
+Usage::
+
+    browserver.py -h
+    browserver.py [-s] [-p <port>]
+
+Options::
+
+    -h or --help
+        Display this help message.
+
+    -l <file> or --log-file <file>
+        Logs messages to the given file, If this option is not specified
+        messages are silently dropped.
+
+    -p <port> or --port <port>
+        Run the web server on this TCP port, defaults to 8000.
+
+    -s or --server-mode
+        Do not start a web browser, and do not allow a user to
+        shutdown the server through the web interface.
+"""
+# TODO: throughout this package variable names and docstrings need
+# modifying to be compliant with NLTK's coding standards.  Tests also
+# need to be develop to ensure this continues to work in the face of
+# changes to other NLTK packages.
+
+import base64
+import copy
+import getopt
+import io
+import os
+import pickle
+import sys
+import threading
+import time
+import webbrowser
+from collections import defaultdict
+from http.server import BaseHTTPRequestHandler, HTTPServer
+
+# Allow this program to run inside the NLTK source tree.
+from sys import argv
+from urllib.parse import unquote_plus
+
+from nltk.corpus import wordnet as wn
+from nltk.corpus.reader.wordnet import Lemma, Synset
+
+firstClient = True
+
+# True if we're not also running a web browser.  The value f server_mode
+# gets set by demo().
+server_mode = None
+
+# If set this is a file object for writing log messages.
+logfile = None
+
+
+class MyServerHandler(BaseHTTPRequestHandler):
+    def do_HEAD(self):
+        self.send_head()
+
+    def do_GET(self):
+        global firstClient
+        sp = self.path[1:]
+        if unquote_plus(sp) == "SHUTDOWN THE SERVER":
+            if server_mode:
+                page = "Server must be killed with SIGTERM."
+                type = "text/plain"
+            else:
+                print("Server shutting down!")
+                os._exit(0)
+
+        elif sp == "":  # First request.
+            type = "text/html"
+            if not server_mode and firstClient:
+                firstClient = False
+                page = get_static_index_page(True)
+            else:
+                page = get_static_index_page(False)
+            word = "green"
+
+        elif sp.endswith(".html"):  # Trying to fetch a HTML file TODO:
+            type = "text/html"
+            usp = unquote_plus(sp)
+            if usp == "NLTK Wordnet Browser Database Info.html":
+                word = "* Database Info *"
+                if os.path.isfile(usp):
+                    with open(usp) as infile:
+                        page = infile.read()
+                else:
+                    page = (
+                        (html_header % word) + "<p>The database info file:"
+                        "<p><b>"
+                        + usp
+                        + "</b>"
+                        + "<p>was not found. Run this:"
+                        + "<p><b>python dbinfo_html.py</b>"
+                        + "<p>to produce it."
+                        + html_trailer
+                    )
+            else:
+                # Handle files here.
+                word = sp
+                try:
+                    page = get_static_page_by_path(usp)
+                except FileNotFoundError:
+                    page = "Internal error: Path for static page '%s' is unknown" % usp
+                    # Set type to plain to prevent XSS by printing the path as HTML
+                    type = "text/plain"
+        elif sp.startswith("search"):
+            # This doesn't seem to work with MWEs.
+            type = "text/html"
+            parts = (sp.split("?")[1]).split("&")
+            word = [
+                p.split("=")[1].replace("+", " ")
+                for p in parts
+                if p.startswith("nextWord")
+            ][0]
+            page, word = page_from_word(word)
+        elif sp.startswith("lookup_"):
+            # TODO add a variation of this that takes a non ecoded word or MWE.
+            type = "text/html"
+            sp = sp[len("lookup_") :]
+            page, word = page_from_href(sp)
+        elif sp == "start_page":
+            # if this is the first request we should display help
+            # information, and possibly set a default word.
+            type = "text/html"
+            page, word = page_from_word("wordnet")
+        else:
+            type = "text/plain"
+            page = "Could not parse request: '%s'" % sp
+
+        # Send result.
+        self.send_head(type)
+        self.wfile.write(page.encode("utf8"))
+
+    def send_head(self, type=None):
+        self.send_response(200)
+        self.send_header("Content-type", type)
+        self.end_headers()
+
+    def log_message(self, format, *args):
+        global logfile
+
+        if logfile:
+            logfile.write(
+                "%s - - [%s] %s\n"
+                % (self.address_string(), self.log_date_time_string(), format % args)
+            )
+
+
+def get_unique_counter_from_url(sp):
+    """
+    Extract the unique counter from the URL if it has one.  Otherwise return
+    null.
+    """
+    pos = sp.rfind("%23")
+    if pos != -1:
+        return int(sp[(pos + 3) :])
+    else:
+        return None
+
+
+def wnb(port=8000, runBrowser=True, logfilename=None):
+    """
+    Run NLTK Wordnet Browser Server.
+
+    :param port: The port number for the server to listen on, defaults to
+                 8000
+    :type  port: int
+
+    :param runBrowser: True to start a web browser and point it at the web
+                       server.
+    :type  runBrowser: bool
+    """
+    # The webbrowser module is unpredictable, typically it blocks if it uses
+    # a console web browser, and doesn't block if it uses a GUI webbrowser,
+    # so we need to force it to have a clear correct behaviour.
+    #
+    # Normally the server should run for as long as the user wants. they
+    # should idealy be able to control this from the UI by closing the
+    # window or tab.  Second best would be clicking a button to say
+    # 'Shutdown' that first shutsdown the server and closes the window or
+    # tab, or exits the text-mode browser.  Both of these are unfreasable.
+    #
+    # The next best alternative is to start the server, have it close when
+    # it receives SIGTERM (default), and run the browser as well.  The user
+    # may have to shutdown both programs.
+    #
+    # Since webbrowser may block, and the webserver will block, we must run
+    # them in separate threads.
+    #
+    global server_mode, logfile
+    server_mode = not runBrowser
+
+    # Setup logging.
+    if logfilename:
+        try:
+            logfile = open(logfilename, "a", 1)  # 1 means 'line buffering'
+        except OSError as e:
+            sys.stderr.write("Couldn't open %s for writing: %s", logfilename, e)
+            sys.exit(1)
+    else:
+        logfile = None
+
+    # Compute URL and start web browser
+    url = "http://localhost:" + str(port)
+
+    server_ready = None
+    browser_thread = None
+
+    if runBrowser:
+        server_ready = threading.Event()
+        browser_thread = startBrowser(url, server_ready)
+
+    # Start the server.
+    server = HTTPServer(("", port), MyServerHandler)
+    if logfile:
+        logfile.write("NLTK Wordnet browser server running serving: %s\n" % url)
+    if runBrowser:
+        server_ready.set()
+
+    try:
+        server.serve_forever()
+    except KeyboardInterrupt:
+        pass
+
+    if runBrowser:
+        browser_thread.join()
+
+    if logfile:
+        logfile.close()
+
+
+def startBrowser(url, server_ready):
+    def run():
+        server_ready.wait()
+        time.sleep(1)  # Wait a little bit more, there's still the chance of
+        # a race condition.
+        webbrowser.open(url, new=2, autoraise=1)
+
+    t = threading.Thread(target=run)
+    t.start()
+    return t
+
+
+#####################################################################
+# Utilities
+#####################################################################
+
+
+"""
+WordNet Browser Utilities.
+
+This provides a backend to both wxbrowse and browserver.py.
+"""
+
+################################################################################
+#
+# Main logic for wordnet browser.
+#
+
+
+# This is wrapped inside a function since wn is only available if the
+# WordNet corpus is installed.
+def _pos_tuples():
+    return [
+        (wn.NOUN, "N", "noun"),
+        (wn.VERB, "V", "verb"),
+        (wn.ADJ, "J", "adj"),
+        (wn.ADV, "R", "adv"),
+    ]
+
+
+def _pos_match(pos_tuple):
+    """
+    This function returns the complete pos tuple for the partial pos
+    tuple given to it.  It attempts to match it against the first
+    non-null component of the given pos tuple.
+    """
+    if pos_tuple[0] == "s":
+        pos_tuple = ("a", pos_tuple[1], pos_tuple[2])
+    for n, x in enumerate(pos_tuple):
+        if x is not None:
+            break
+    for pt in _pos_tuples():
+        if pt[n] == pos_tuple[n]:
+            return pt
+    return None
+
+
+HYPONYM = 0
+HYPERNYM = 1
+CLASS_REGIONAL = 2
+PART_HOLONYM = 3
+PART_MERONYM = 4
+ATTRIBUTE = 5
+SUBSTANCE_HOLONYM = 6
+SUBSTANCE_MERONYM = 7
+MEMBER_HOLONYM = 8
+MEMBER_MERONYM = 9
+VERB_GROUP = 10
+INSTANCE_HYPONYM = 12
+INSTANCE_HYPERNYM = 13
+CAUSE = 14
+ALSO_SEE = 15
+SIMILAR = 16
+ENTAILMENT = 17
+ANTONYM = 18
+FRAMES = 19
+PERTAINYM = 20
+
+CLASS_CATEGORY = 21
+CLASS_USAGE = 22
+CLASS_REGIONAL = 23
+CLASS_USAGE = 24
+CLASS_CATEGORY = 11
+
+DERIVATIONALLY_RELATED_FORM = 25
+
+INDIRECT_HYPERNYMS = 26
+
+
+def lemma_property(word, synset, func):
+    def flattern(l):
+        if l == []:
+            return []
+        else:
+            return l[0] + flattern(l[1:])
+
+    return flattern([func(l) for l in synset.lemmas() if l.name == word])
+
+
+def rebuild_tree(orig_tree):
+    node = orig_tree[0]
+    children = orig_tree[1:]
+    return (node, [rebuild_tree(t) for t in children])
+
+
+def get_relations_data(word, synset):
+    """
+    Get synset relations data for a synset.  Note that this doesn't
+    yet support things such as full hyponym vs direct hyponym.
+    """
+    if synset.pos() == wn.NOUN:
+        return (
+            (HYPONYM, "Hyponyms", synset.hyponyms()),
+            (INSTANCE_HYPONYM, "Instance hyponyms", synset.instance_hyponyms()),
+            (HYPERNYM, "Direct hypernyms", synset.hypernyms()),
+            (
+                INDIRECT_HYPERNYMS,
+                "Indirect hypernyms",
+                rebuild_tree(synset.tree(lambda x: x.hypernyms()))[1],
+            ),
+            #  hypernyms', 'Sister terms',
+            (INSTANCE_HYPERNYM, "Instance hypernyms", synset.instance_hypernyms()),
+            #            (CLASS_REGIONAL, ['domain term region'], ),
+            (PART_HOLONYM, "Part holonyms", synset.part_holonyms()),
+            (PART_MERONYM, "Part meronyms", synset.part_meronyms()),
+            (SUBSTANCE_HOLONYM, "Substance holonyms", synset.substance_holonyms()),
+            (SUBSTANCE_MERONYM, "Substance meronyms", synset.substance_meronyms()),
+            (MEMBER_HOLONYM, "Member holonyms", synset.member_holonyms()),
+            (MEMBER_MERONYM, "Member meronyms", synset.member_meronyms()),
+            (ATTRIBUTE, "Attributes", synset.attributes()),
+            (ANTONYM, "Antonyms", lemma_property(word, synset, lambda l: l.antonyms())),
+            (
+                DERIVATIONALLY_RELATED_FORM,
+                "Derivationally related form",
+                lemma_property(
+                    word, synset, lambda l: l.derivationally_related_forms()
+                ),
+            ),
+        )
+    elif synset.pos() == wn.VERB:
+        return (
+            (ANTONYM, "Antonym", lemma_property(word, synset, lambda l: l.antonyms())),
+            (HYPONYM, "Hyponym", synset.hyponyms()),
+            (HYPERNYM, "Direct hypernyms", synset.hypernyms()),
+            (
+                INDIRECT_HYPERNYMS,
+                "Indirect hypernyms",
+                rebuild_tree(synset.tree(lambda x: x.hypernyms()))[1],
+            ),
+            (ENTAILMENT, "Entailments", synset.entailments()),
+            (CAUSE, "Causes", synset.causes()),
+            (ALSO_SEE, "Also see", synset.also_sees()),
+            (VERB_GROUP, "Verb Groups", synset.verb_groups()),
+            (
+                DERIVATIONALLY_RELATED_FORM,
+                "Derivationally related form",
+                lemma_property(
+                    word, synset, lambda l: l.derivationally_related_forms()
+                ),
+            ),
+        )
+    elif synset.pos() == wn.ADJ or synset.pos == wn.ADJ_SAT:
+        return (
+            (ANTONYM, "Antonym", lemma_property(word, synset, lambda l: l.antonyms())),
+            (SIMILAR, "Similar to", synset.similar_tos()),
+            # Participle of verb - not supported by corpus
+            (
+                PERTAINYM,
+                "Pertainyms",
+                lemma_property(word, synset, lambda l: l.pertainyms()),
+            ),
+            (ATTRIBUTE, "Attributes", synset.attributes()),
+            (ALSO_SEE, "Also see", synset.also_sees()),
+        )
+    elif synset.pos() == wn.ADV:
+        # This is weird. adverbs such as 'quick' and 'fast' don't seem
+        # to have antonyms returned by the corpus.a
+        return (
+            (ANTONYM, "Antonym", lemma_property(word, synset, lambda l: l.antonyms())),
+        )
+        # Derived from adjective - not supported by corpus
+    else:
+        raise TypeError("Unhandles synset POS type: " + str(synset.pos()))
+
+
+html_header = """
+<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
+'http://www.w3.org/TR/html4/strict.dtd'>
+<html>
+<head>
+<meta name='generator' content=
+'HTML Tidy for Windows (vers 14 February 2006), see www.w3.org'>
+<meta http-equiv='Content-Type' content=
+'text/html; charset=us-ascii'>
+<title>NLTK Wordnet Browser display of: %s</title></head>
+<body bgcolor='#F5F5F5' text='#000000'>
+"""
+html_trailer = """
+</body>
+</html>
+"""
+
+explanation = """
+<h3>Search Help</h3>
+<ul><li>The display below the line is an example of the output the browser
+shows you when you enter a search word. The search word was <b>green</b>.</li>
+<li>The search result shows for different parts of speech the <b>synsets</b>
+i.e. different meanings for the word.</li>
+<li>All underlined texts are hypertext links. There are two types of links:
+word links and others. Clicking a word link carries out a search for the word
+in the Wordnet database.</li>
+<li>Clicking a link of the other type opens a display section of data attached
+to that link. Clicking that link a second time closes the section again.</li>
+<li>Clicking <u>S:</u> opens a section showing the relations for that synset.
+</li>
+<li>Clicking on a relation name opens a section that displays the associated
+synsets.</li>
+<li>Type a search word in the <b>Word</b> field and start the search by the
+<b>Enter/Return</b> key or click the <b>Search</b> button.</li>
+</ul>
+<hr width='100%'>
+"""
+
+# HTML oriented functions
+
+
+def _bold(txt):
+    return "<b>%s</b>" % txt
+
+
+def _center(txt):
+    return "<center>%s</center>" % txt
+
+
+def _hlev(n, txt):
+    return "<h%d>%s</h%d>" % (n, txt, n)
+
+
+def _italic(txt):
+    return "<i>%s</i>" % txt
+
+
+def _li(txt):
+    return "<li>%s</li>" % txt
+
+
+def pg(word, body):
+    """
+    Return a HTML page of NLTK Browser format constructed from the
+    word and body
+
+    :param word: The word that the body corresponds to
+    :type word: str
+    :param body: The HTML body corresponding to the word
+    :type body: str
+    :return: a HTML page for the word-body combination
+    :rtype: str
+    """
+    return (html_header % word) + body + html_trailer
+
+
+def _ul(txt):
+    return "<ul>" + txt + "</ul>"
+
+
+def _abbc(txt):
+    """
+    abbc = asterisks, breaks, bold, center
+    """
+    return _center(_bold("<br>" * 10 + "*" * 10 + " " + txt + " " + "*" * 10))
+
+
+full_hyponym_cont_text = _ul(_li(_italic("(has full hyponym continuation)"))) + "\n"
+
+
+def _get_synset(synset_key):
+    """
+    The synset key is the unique name of the synset, this can be
+    retrieved via synset.name()
+    """
+    return wn.synset(synset_key)
+
+
+def _collect_one_synset(word, synset, synset_relations):
+    """
+    Returns the HTML string for one synset or word
+
+    :param word: the current word
+    :type word: str
+    :param synset: a synset
+    :type synset: synset
+    :param synset_relations: information about which synset relations
+    to display.
+    :type synset_relations: dict(synset_key, set(relation_id))
+    :return: The HTML string built for this synset
+    :rtype: str
+    """
+    if isinstance(synset, tuple):  # It's a word
+        raise NotImplementedError("word not supported by _collect_one_synset")
+
+    typ = "S"
+    pos_tuple = _pos_match((synset.pos(), None, None))
+    assert pos_tuple is not None, "pos_tuple is null: synset.pos(): %s" % synset.pos()
+    descr = pos_tuple[2]
+    ref = copy.deepcopy(Reference(word, synset_relations))
+    ref.toggle_synset(synset)
+    synset_label = typ + ";"
+    if synset.name() in synset_relations:
+        synset_label = _bold(synset_label)
+    s = f"<li>{make_lookup_link(ref, synset_label)} ({descr}) "
+
+    def format_lemma(w):
+        w = w.replace("_", " ")
+        if w.lower() == word:
+            return _bold(w)
+        else:
+            ref = Reference(w)
+            return make_lookup_link(ref, w)
+
+    s += ", ".join(format_lemma(l.name()) for l in synset.lemmas())
+
+    gl = " ({}) <i>{}</i> ".format(
+        synset.definition(),
+        "; ".join('"%s"' % e for e in synset.examples()),
+    )
+    return s + gl + _synset_relations(word, synset, synset_relations) + "</li>\n"
+
+
+def _collect_all_synsets(word, pos, synset_relations=dict()):
+    """
+    Return a HTML unordered list of synsets for the given word and
+    part of speech.
+    """
+    return "<ul>%s\n</ul>\n" % "".join(
+        _collect_one_synset(word, synset, synset_relations)
+        for synset in wn.synsets(word, pos)
+    )
+
+
+def _synset_relations(word, synset, synset_relations):
+    """
+    Builds the HTML string for the relations of a synset
+
+    :param word: The current word
+    :type word: str
+    :param synset: The synset for which we're building the relations.
+    :type synset: Synset
+    :param synset_relations: synset keys and relation types for which to display relations.
+    :type synset_relations: dict(synset_key, set(relation_type))
+    :return: The HTML for a synset's relations
+    :rtype: str
+    """
+
+    if not synset.name() in synset_relations:
+        return ""
+    ref = Reference(word, synset_relations)
+
+    def relation_html(r):
+        if isinstance(r, Synset):
+            return make_lookup_link(Reference(r.lemma_names()[0]), r.lemma_names()[0])
+        elif isinstance(r, Lemma):
+            return relation_html(r.synset())
+        elif isinstance(r, tuple):
+            # It's probably a tuple containing a Synset and a list of
+            # similar tuples.  This forms a tree of synsets.
+            return "{}\n<ul>{}</ul>\n".format(
+                relation_html(r[0]),
+                "".join("<li>%s</li>\n" % relation_html(sr) for sr in r[1]),
+            )
+        else:
+            raise TypeError(
+                "r must be a synset, lemma or list, it was: type(r) = %s, r = %s"
+                % (type(r), r)
+            )
+
+    def make_synset_html(db_name, disp_name, rels):
+        synset_html = "<i>%s</i>\n" % make_lookup_link(
+            copy.deepcopy(ref).toggle_synset_relation(synset, db_name),
+            disp_name,
+        )
+
+        if db_name in ref.synset_relations[synset.name()]:
+            synset_html += "<ul>%s</ul>\n" % "".join(
+                "<li>%s</li>\n" % relation_html(r) for r in rels
+            )
+
+        return synset_html
+
+    html = (
+        "<ul>"
+        + "\n".join(
+            "<li>%s</li>" % make_synset_html(*rel_data)
+            for rel_data in get_relations_data(word, synset)
+            if rel_data[2] != []
+        )
+        + "</ul>"
+    )
+
+    return html
+
+
+class RestrictedUnpickler(pickle.Unpickler):
+    """
+    Unpickler that prevents any class or function from being used during loading.
+    """
+
+    def find_class(self, module, name):
+        # Forbid every function
+        raise pickle.UnpicklingError(f"global '{module}.{name}' is forbidden")
+
+
+class Reference:
+    """
+    A reference to a page that may be generated by page_word
+    """
+
+    def __init__(self, word, synset_relations=dict()):
+        """
+        Build a reference to a new page.
+
+        word is the word or words (separated by commas) for which to
+        search for synsets of
+
+        synset_relations is a dictionary of synset keys to sets of
+        synset relation identifaiers to unfold a list of synset
+        relations for.
+        """
+        self.word = word
+        self.synset_relations = synset_relations
+
+    def encode(self):
+        """
+        Encode this reference into a string to be used in a URL.
+        """
+        # This uses a tuple rather than an object since the python
+        # pickle representation is much smaller and there is no need
+        # to represent the complete object.
+        string = pickle.dumps((self.word, self.synset_relations), -1)
+        return base64.urlsafe_b64encode(string).decode()
+
+    @staticmethod
+    def decode(string):
+        """
+        Decode a reference encoded with Reference.encode
+        """
+        string = base64.urlsafe_b64decode(string.encode())
+        word, synset_relations = RestrictedUnpickler(io.BytesIO(string)).load()
+        return Reference(word, synset_relations)
+
+    def toggle_synset_relation(self, synset, relation):
+        """
+        Toggle the display of the relations for the given synset and
+        relation type.
+
+        This function will throw a KeyError if the synset is currently
+        not being displayed.
+        """
+        if relation in self.synset_relations[synset.name()]:
+            self.synset_relations[synset.name()].remove(relation)
+        else:
+            self.synset_relations[synset.name()].add(relation)
+
+        return self
+
+    def toggle_synset(self, synset):
+        """
+        Toggle displaying of the relation types for the given synset
+        """
+        if synset.name() in self.synset_relations:
+            del self.synset_relations[synset.name()]
+        else:
+            self.synset_relations[synset.name()] = set()
+
+        return self
+
+
+def make_lookup_link(ref, label):
+    return f'<a href="lookup_{ref.encode()}">{label}</a>'
+
+
+def page_from_word(word):
+    """
+    Return a HTML page for the given word.
+
+    :type word: str
+    :param word: The currently active word
+    :return: A tuple (page,word), where page is the new current HTML page
+        to be sent to the browser and
+        word is the new current word
+    :rtype: A tuple (str,str)
+    """
+    return page_from_reference(Reference(word))
+
+
+def page_from_href(href):
+    """
+    Returns a tuple of the HTML page built and the new current word
+
+    :param href: The hypertext reference to be solved
+    :type href: str
+    :return: A tuple (page,word), where page is the new current HTML page
+             to be sent to the browser and
+             word is the new current word
+    :rtype: A tuple (str,str)
+    """
+    return page_from_reference(Reference.decode(href))
+
+
+def page_from_reference(href):
+    """
+    Returns a tuple of the HTML page built and the new current word
+
+    :param href: The hypertext reference to be solved
+    :type href: str
+    :return: A tuple (page,word), where page is the new current HTML page
+             to be sent to the browser and
+             word is the new current word
+    :rtype: A tuple (str,str)
+    """
+    word = href.word
+    pos_forms = defaultdict(list)
+    words = word.split(",")
+    words = [w for w in [w.strip().lower().replace(" ", "_") for w in words] if w != ""]
+    if len(words) == 0:
+        # No words were found.
+        return "", "Please specify a word to search for."
+
+    # This looks up multiple words at once.  This is probably not
+    # necessary and may lead to problems.
+    for w in words:
+        for pos in [wn.NOUN, wn.VERB, wn.ADJ, wn.ADV]:
+            form = wn.morphy(w, pos)
+            if form and form not in pos_forms[pos]:
+                pos_forms[pos].append(form)
+    body = ""
+    for pos, pos_str, name in _pos_tuples():
+        if pos in pos_forms:
+            body += _hlev(3, name) + "\n"
+            for w in pos_forms[pos]:
+                # Not all words of exc files are in the database, skip
+                # to the next word if a KeyError is raised.
+                try:
+                    body += _collect_all_synsets(w, pos, href.synset_relations)
+                except KeyError:
+                    pass
+    if not body:
+        body = "The word or words '%s' were not found in the dictionary." % word
+    return body, word
+
+
+#####################################################################
+# Static pages
+#####################################################################
+
+
+def get_static_page_by_path(path):
+    """
+    Return a static HTML page from the path given.
+    """
+    if path == "index_2.html":
+        return get_static_index_page(False)
+    elif path == "index.html":
+        return get_static_index_page(True)
+    elif path == "NLTK Wordnet Browser Database Info.html":
+        return "Display of Wordnet Database Statistics is not supported"
+    elif path == "upper_2.html":
+        return get_static_upper_page(False)
+    elif path == "upper.html":
+        return get_static_upper_page(True)
+    elif path == "web_help.html":
+        return get_static_web_help_page()
+    elif path == "wx_help.html":
+        return get_static_wx_help_page()
+    raise FileNotFoundError()
+
+
+def get_static_web_help_page():
+    """
+    Return the static web help page.
+    """
+    return """
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+     <!-- Natural Language Toolkit: Wordnet Interface: Graphical Wordnet Browser
+            Copyright (C) 2001-2024 NLTK Project
+            Author: Jussi Salmela <[email protected]>
+            URL: <https://www.nltk.org/>
+            For license information, see LICENSE.TXT -->
+     <head>
+          <meta http-equiv='Content-Type' content='text/html; charset=us-ascii'>
+          <title>NLTK Wordnet Browser display of: * Help *</title>
+     </head>
+<body bgcolor='#F5F5F5' text='#000000'>
+<h2>NLTK Wordnet Browser Help</h2>
+<p>The NLTK Wordnet Browser is a tool to use in browsing the Wordnet database. It tries to behave like the Wordnet project's web browser but the difference is that the NLTK Wordnet Browser uses a local Wordnet database.
+<p><b>You are using the Javascript client part of the NLTK Wordnet BrowseServer.</b> We assume your browser is in tab sheets enabled mode.</p>
+<p>For background information on Wordnet, see the Wordnet project home page: <a href="https://wordnet.princeton.edu/"><b> https://wordnet.princeton.edu/</b></a>. For more information on the NLTK project, see the project home:
+<a href="https://www.nltk.org/"><b>https://www.nltk.org/</b></a>. To get an idea of what the Wordnet version used by this browser includes choose <b>Show Database Info</b> from the <b>View</b> submenu.</p>
+<h3>Word search</h3>
+<p>The word to be searched is typed into the <b>New Word</b> field and the search started with Enter or by clicking the <b>Search</b> button. There is no uppercase/lowercase distinction: the search word is transformed to lowercase before the search.</p>
+<p>In addition, the word does not have to be in base form. The browser tries to find the possible base form(s) by making certain morphological substitutions. Typing <b>fLIeS</b> as an obscure example gives one <a href="MfLIeS">this</a>. Click the previous link to see what this kind of search looks like and then come back to this page by using the <b>Alt+LeftArrow</b> key combination.</p>
+<p>The result of a search is a display of one or more
+<b>synsets</b> for every part of speech in which a form of the
+search word was found to occur. A synset is a set of words
+having the same sense or meaning. Each word in a synset that is
+underlined is a hyperlink which can be clicked to trigger an
+automatic search for that word.</p>
+<p>Every synset has a hyperlink <b>S:</b> at the start of its
+display line. Clicking that symbol shows you the name of every
+<b>relation</b> that this synset is part of. Every relation name is a hyperlink that opens up a display for that relation. Clicking it another time closes the display again. Clicking another relation name on a line that has an opened relation closes the open relation and opens the clicked relation.</p>
+<p>It is also possible to give two or more words or collocations to be searched at the same time separating them with a comma like this <a href="Mcheer up,clear up">cheer up,clear up</a>, for example. Click the previous link to see what this kind of search looks like and then come back to this page by using the <b>Alt+LeftArrow</b> key combination. As you could see the search result includes the synsets found in the same order than the forms were given in the search field.</p>
+<p>
+There are also word level (lexical) relations recorded in the Wordnet database. Opening this kind of relation displays lines with a hyperlink <b>W:</b> at their beginning. Clicking this link shows more info on the word in question.</p>
+<h3>The Buttons</h3>
+<p>The <b>Search</b> and <b>Help</b> buttons need no more explanation. </p>
+<p>The <b>Show Database Info</b> button shows a collection of Wordnet database statistics.</p>
+<p>The <b>Shutdown the Server</b> button is shown for the first client of the BrowServer program i.e. for the client that is automatically launched when the BrowServer is started but not for the succeeding clients in order to protect the server from accidental shutdowns.
+</p></body>
+</html>
+"""
+
+
+def get_static_welcome_message():
+    """
+    Get the static welcome page.
+    """
+    return """
+<h3>Search Help</h3>
+<ul><li>The display below the line is an example of the output the browser
+shows you when you enter a search word. The search word was <b>green</b>.</li>
+<li>The search result shows for different parts of speech the <b>synsets</b>
+i.e. different meanings for the word.</li>
+<li>All underlined texts are hypertext links. There are two types of links:
+word links and others. Clicking a word link carries out a search for the word
+in the Wordnet database.</li>
+<li>Clicking a link of the other type opens a display section of data attached
+to that link. Clicking that link a second time closes the section again.</li>
+<li>Clicking <u>S:</u> opens a section showing the relations for that synset.</li>
+<li>Clicking on a relation name opens a section that displays the associated
+synsets.</li>
+<li>Type a search word in the <b>Next Word</b> field and start the search by the
+<b>Enter/Return</b> key or click the <b>Search</b> button.</li>
+</ul>
+"""
+
+
+def get_static_index_page(with_shutdown):
+    """
+    Get the static index page.
+    """
+    template = """
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN"  "http://www.w3.org/TR/html4/frameset.dtd">
+<HTML>
+     <!-- Natural Language Toolkit: Wordnet Interface: Graphical Wordnet Browser
+            Copyright (C) 2001-2024 NLTK Project
+            Author: Jussi Salmela <[email protected]>
+            URL: <https://www.nltk.org/>
+            For license information, see LICENSE.TXT -->
+     <HEAD>
+         <TITLE>NLTK Wordnet Browser</TITLE>
+     </HEAD>
+
+<frameset rows="7%%,93%%">
+    <frame src="%s" name="header">
+    <frame src="start_page" name="body">
+</frameset>
+</HTML>
+"""
+    if with_shutdown:
+        upper_link = "upper.html"
+    else:
+        upper_link = "upper_2.html"
+
+    return template % upper_link
+
+
+def get_static_upper_page(with_shutdown):
+    """
+    Return the upper frame page,
+
+    If with_shutdown is True then a 'shutdown' button is also provided
+    to shutdown the server.
+    """
+    template = """
+<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
+<html>
+    <!-- Natural Language Toolkit: Wordnet Interface: Graphical Wordnet Browser
+        Copyright (C) 2001-2024 NLTK Project
+        Author: Jussi Salmela <[email protected]>
+        URL: <https://www.nltk.org/>
+        For license information, see LICENSE.TXT -->
+    <head>
+                <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
+        <title>Untitled Document</title>
+    </head>
+    <body>
+    <form method="GET" action="search" target="body">
+            Current Word:&nbsp;<input type="text" id="currentWord" size="10" disabled>
+            Next Word:&nbsp;<input type="text" id="nextWord" name="nextWord" size="10">
+            <input name="searchButton" type="submit" value="Search">
+    </form>
+        <a target="body" href="web_help.html">Help</a>
+        %s
+
+</body>
+</html>
+"""
+    if with_shutdown:
+        shutdown_link = '<a href="SHUTDOWN THE SERVER">Shutdown</a>'
+    else:
+        shutdown_link = ""
+
+    return template % shutdown_link
+
+
+def usage():
+    """
+    Display the command line help message.
+    """
+    print(__doc__)
+
+
+def app():
+    # Parse and interpret options.
+    (opts, _) = getopt.getopt(
+        argv[1:], "l:p:sh", ["logfile=", "port=", "server-mode", "help"]
+    )
+    port = 8000
+    server_mode = False
+    help_mode = False
+    logfilename = None
+    for opt, value in opts:
+        if (opt == "-l") or (opt == "--logfile"):
+            logfilename = str(value)
+        elif (opt == "-p") or (opt == "--port"):
+            port = int(value)
+        elif (opt == "-s") or (opt == "--server-mode"):
+            server_mode = True
+        elif (opt == "-h") or (opt == "--help"):
+            help_mode = True
+
+    if help_mode:
+        usage()
+    else:
+        wnb(port, not server_mode, logfilename)
+
+
+if __name__ == "__main__":
+    app()
+
+__all__ = ["app"]

infer_4_37_2/lib/python3.10/site-packages/nltk/corpus/reader/__pycache__/framenet.cpython-310.pyc

@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:30ad80fe6f9214154e7d20833711fb6a188a2a8b9e2f84bb0330c95447e150b5
+size 104612

infer_4_37_2/lib/python3.10/site-packages/nltk/parse/api.py

@@ -0,0 +1,72 @@
+# Natural Language Toolkit: Parser API
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Steven Bird <[email protected]>
+#         Edward Loper <[email protected]>
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+#
+
+import itertools
+
+from nltk.internals import overridden
+
+
+class ParserI:
+    """
+    A processing class for deriving trees that represent possible
+    structures for a sequence of tokens.  These tree structures are
+    known as "parses".  Typically, parsers are used to derive syntax
+    trees for sentences.  But parsers can also be used to derive other
+    kinds of tree structure, such as morphological trees and discourse
+    structures.
+
+    Subclasses must define:
+      - at least one of: ``parse()``, ``parse_sents()``.
+
+    Subclasses may define:
+      - ``grammar()``
+    """
+
+    def grammar(self):
+        """
+        :return: The grammar used by this parser.
+        """
+        raise NotImplementedError()
+
+    def parse(self, sent, *args, **kwargs):
+        """
+        :return: An iterator that generates parse trees for the sentence.
+            When possible this list is sorted from most likely to least likely.
+
+        :param sent: The sentence to be parsed
+        :type sent: list(str)
+        :rtype: iter(Tree)
+        """
+        if overridden(self.parse_sents):
+            return next(self.parse_sents([sent], *args, **kwargs))
+        elif overridden(self.parse_one):
+            return (
+                tree
+                for tree in [self.parse_one(sent, *args, **kwargs)]
+                if tree is not None
+            )
+        elif overridden(self.parse_all):
+            return iter(self.parse_all(sent, *args, **kwargs))
+        else:
+            raise NotImplementedError()
+
+    def parse_sents(self, sents, *args, **kwargs):
+        """
+        Apply ``self.parse()`` to each element of ``sents``.
+        :rtype: iter(iter(Tree))
+        """
+        return (self.parse(sent, *args, **kwargs) for sent in sents)
+
+    def parse_all(self, sent, *args, **kwargs):
+        """:rtype: list(Tree)"""
+        return list(self.parse(sent, *args, **kwargs))
+
+    def parse_one(self, sent, *args, **kwargs):
+        """:rtype: Tree or None"""
+        return next(self.parse(sent, *args, **kwargs), None)

infer_4_37_2/lib/python3.10/site-packages/nltk/parse/bllip.py

@@ -0,0 +1,299 @@
+# Natural Language Toolkit: Interface to BLLIP Parser
+#
+# Author: David McClosky <[email protected]>
+#
+# Copyright (C) 2001-2024 NLTK Project
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+from nltk.parse.api import ParserI
+from nltk.tree import Tree
+
+"""
+Interface for parsing with BLLIP Parser. Requires the Python
+bllipparser module. BllipParser objects can be constructed with the
+``BllipParser.from_unified_model_dir`` class method or manually using the
+``BllipParser`` constructor. The former is generally easier if you have
+a BLLIP Parser unified model directory -- a basic model can be obtained
+from NLTK's downloader. More unified parsing models can be obtained with
+BLLIP Parser's ModelFetcher (run ``python -m bllipparser.ModelFetcher``
+or see docs for ``bllipparser.ModelFetcher.download_and_install_model``).
+
+Basic usage::
+
+    # download and install a basic unified parsing model (Wall Street Journal)
+    # sudo python -m nltk.downloader bllip_wsj_no_aux
+
+    >>> from nltk.data import find
+    >>> model_dir = find('models/bllip_wsj_no_aux').path
+    >>> bllip = BllipParser.from_unified_model_dir(model_dir)
+
+    # 1-best parsing
+    >>> sentence1 = 'British left waffles on Falklands .'.split()
+    >>> top_parse = bllip.parse_one(sentence1)
+    >>> print(top_parse)
+    (S1
+      (S
+        (NP (JJ British) (NN left))
+        (VP (VBZ waffles) (PP (IN on) (NP (NNP Falklands))))
+        (. .)))
+
+    # n-best parsing
+    >>> sentence2 = 'Time flies'.split()
+    >>> all_parses = bllip.parse_all(sentence2)
+    >>> print(len(all_parses))
+    50
+    >>> print(all_parses[0])
+    (S1 (S (NP (NNP Time)) (VP (VBZ flies))))
+
+    # incorporating external tagging constraints (None means unconstrained tag)
+    >>> constrained1 = bllip.tagged_parse([('Time', 'VB'), ('flies', 'NNS')])
+    >>> print(next(constrained1))
+    (S1 (NP (VB Time) (NNS flies)))
+    >>> constrained2 = bllip.tagged_parse([('Time', 'NN'), ('flies', None)])
+    >>> print(next(constrained2))
+    (S1 (NP (NN Time) (VBZ flies)))
+
+References
+----------
+
+- Charniak, Eugene. "A maximum-entropy-inspired parser." Proceedings of
+  the 1st North American chapter of the Association for Computational
+  Linguistics conference. Association for Computational Linguistics,
+  2000.
+
+- Charniak, Eugene, and Mark Johnson. "Coarse-to-fine n-best parsing
+  and MaxEnt discriminative reranking." Proceedings of the 43rd Annual
+  Meeting on Association for Computational Linguistics. Association
+  for Computational Linguistics, 2005.
+
+Known issues
+------------
+
+Note that BLLIP Parser is not currently threadsafe. Since this module
+uses a SWIG interface, it is potentially unsafe to create multiple
+``BllipParser`` objects in the same process. BLLIP Parser currently
+has issues with non-ASCII text and will raise an error if given any.
+
+See https://pypi.python.org/pypi/bllipparser/ for more information
+on BLLIP Parser's Python interface.
+"""
+
+__all__ = ["BllipParser"]
+
+# this block allows this module to be imported even if bllipparser isn't
+# available
+try:
+    from bllipparser import RerankingParser
+    from bllipparser.RerankingParser import get_unified_model_parameters
+
+    def _ensure_bllip_import_or_error():
+        pass
+
+except ImportError as ie:
+
+    def _ensure_bllip_import_or_error(ie=ie):
+        raise ImportError("Couldn't import bllipparser module: %s" % ie)
+
+
+def _ensure_ascii(words):
+    try:
+        for i, word in enumerate(words):
+            word.encode("ascii")
+    except UnicodeEncodeError as e:
+        raise ValueError(
+            f"Token {i} ({word!r}) is non-ASCII. BLLIP Parser "
+            "currently doesn't support non-ASCII inputs."
+        ) from e
+
+
+def _scored_parse_to_nltk_tree(scored_parse):
+    return Tree.fromstring(str(scored_parse.ptb_parse))
+
+
+class BllipParser(ParserI):
+    """
+    Interface for parsing with BLLIP Parser. BllipParser objects can be
+    constructed with the ``BllipParser.from_unified_model_dir`` class
+    method or manually using the ``BllipParser`` constructor.
+    """
+
+    def __init__(
+        self,
+        parser_model=None,
+        reranker_features=None,
+        reranker_weights=None,
+        parser_options=None,
+        reranker_options=None,
+    ):
+        """
+        Load a BLLIP Parser model from scratch. You'll typically want to
+        use the ``from_unified_model_dir()`` class method to construct
+        this object.
+
+        :param parser_model: Path to parser model directory
+        :type parser_model: str
+
+        :param reranker_features: Path the reranker model's features file
+        :type reranker_features: str
+
+        :param reranker_weights: Path the reranker model's weights file
+        :type reranker_weights: str
+
+        :param parser_options: optional dictionary of parser options, see
+            ``bllipparser.RerankingParser.RerankingParser.load_parser_options()``
+            for more information.
+        :type parser_options: dict(str)
+
+        :param reranker_options: optional
+            dictionary of reranker options, see
+            ``bllipparser.RerankingParser.RerankingParser.load_reranker_model()``
+            for more information.
+        :type reranker_options: dict(str)
+        """
+        _ensure_bllip_import_or_error()
+
+        parser_options = parser_options or {}
+        reranker_options = reranker_options or {}
+
+        self.rrp = RerankingParser()
+        self.rrp.load_parser_model(parser_model, **parser_options)
+        if reranker_features and reranker_weights:
+            self.rrp.load_reranker_model(
+                features_filename=reranker_features,
+                weights_filename=reranker_weights,
+                **reranker_options,
+            )
+
+    def parse(self, sentence):
+        """
+        Use BLLIP Parser to parse a sentence. Takes a sentence as a list
+        of words; it will be automatically tagged with this BLLIP Parser
+        instance's tagger.
+
+        :return: An iterator that generates parse trees for the sentence
+            from most likely to least likely.
+
+        :param sentence: The sentence to be parsed
+        :type sentence: list(str)
+        :rtype: iter(Tree)
+        """
+        _ensure_ascii(sentence)
+        nbest_list = self.rrp.parse(sentence)
+        for scored_parse in nbest_list:
+            yield _scored_parse_to_nltk_tree(scored_parse)
+
+    def tagged_parse(self, word_and_tag_pairs):
+        """
+        Use BLLIP to parse a sentence. Takes a sentence as a list of
+        (word, tag) tuples; the sentence must have already been tokenized
+        and tagged. BLLIP will attempt to use the tags provided but may
+        use others if it can't come up with a complete parse subject
+        to those constraints. You may also specify a tag as ``None``
+        to leave a token's tag unconstrained.
+
+        :return: An iterator that generates parse trees for the sentence
+            from most likely to least likely.
+
+        :param sentence: Input sentence to parse as (word, tag) pairs
+        :type sentence: list(tuple(str, str))
+        :rtype: iter(Tree)
+        """
+        words = []
+        tag_map = {}
+        for i, (word, tag) in enumerate(word_and_tag_pairs):
+            words.append(word)
+            if tag is not None:
+                tag_map[i] = tag
+
+        _ensure_ascii(words)
+        nbest_list = self.rrp.parse_tagged(words, tag_map)
+        for scored_parse in nbest_list:
+            yield _scored_parse_to_nltk_tree(scored_parse)
+
+    @classmethod
+    def from_unified_model_dir(
+        cls, model_dir, parser_options=None, reranker_options=None
+    ):
+        """
+        Create a ``BllipParser`` object from a unified parsing model
+        directory. Unified parsing model directories are a standardized
+        way of storing BLLIP parser and reranker models together on disk.
+        See ``bllipparser.RerankingParser.get_unified_model_parameters()``
+        for more information about unified model directories.
+
+        :return: A ``BllipParser`` object using the parser and reranker
+            models in the model directory.
+
+        :param model_dir: Path to the unified model directory.
+        :type model_dir: str
+        :param parser_options: optional dictionary of parser options, see
+            ``bllipparser.RerankingParser.RerankingParser.load_parser_options()``
+            for more information.
+        :type parser_options: dict(str)
+        :param reranker_options: optional dictionary of reranker options, see
+            ``bllipparser.RerankingParser.RerankingParser.load_reranker_model()``
+            for more information.
+        :type reranker_options: dict(str)
+        :rtype: BllipParser
+        """
+        (
+            parser_model_dir,
+            reranker_features_filename,
+            reranker_weights_filename,
+        ) = get_unified_model_parameters(model_dir)
+        return cls(
+            parser_model_dir,
+            reranker_features_filename,
+            reranker_weights_filename,
+            parser_options,
+            reranker_options,
+        )
+
+
+def demo():
+    """This assumes the Python module bllipparser is installed."""
+
+    # download and install a basic unified parsing model (Wall Street Journal)
+    # sudo python -m nltk.downloader bllip_wsj_no_aux
+
+    from nltk.data import find
+
+    model_dir = find("models/bllip_wsj_no_aux").path
+
+    print("Loading BLLIP Parsing models...")
+    # the easiest way to get started is to use a unified model
+    bllip = BllipParser.from_unified_model_dir(model_dir)
+    print("Done.")
+
+    sentence1 = "British left waffles on Falklands .".split()
+    sentence2 = "I saw the man with the telescope .".split()
+    # this sentence is known to fail under the WSJ parsing model
+    fail1 = "# ! ? : -".split()
+    for sentence in (sentence1, sentence2, fail1):
+        print("Sentence: %r" % " ".join(sentence))
+        try:
+            tree = next(bllip.parse(sentence))
+            print(tree)
+        except StopIteration:
+            print("(parse failed)")
+
+    # n-best parsing demo
+    for i, parse in enumerate(bllip.parse(sentence1)):
+        print("parse %d:\n%s" % (i, parse))
+
+    # using external POS tag constraints
+    print(
+        "forcing 'tree' to be 'NN':",
+        next(bllip.tagged_parse([("A", None), ("tree", "NN")])),
+    )
+    print(
+        "forcing 'A' to be 'DT' and 'tree' to be 'NNP':",
+        next(bllip.tagged_parse([("A", "DT"), ("tree", "NNP")])),
+    )
+    # constraints don't have to make sense... (though on more complicated
+    # sentences, they may cause the parse to fail)
+    print(
+        "forcing 'A' to be 'NNP':",
+        next(bllip.tagged_parse([("A", "NNP"), ("tree", None)])),
+    )

infer_4_37_2/lib/python3.10/site-packages/nltk/parse/chart.py

@@ -0,0 +1,1848 @@
+# Natural Language Toolkit: A Chart Parser
+#
+# Copyright (C) 2001-2024 NLTK Project
+# Author: Edward Loper <[email protected]>
+#         Steven Bird <[email protected]>
+#         Jean Mark Gawron <[email protected]>
+#         Peter Ljunglöf <[email protected]>
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+Data classes and parser implementations for "chart parsers", which
+use dynamic programming to efficiently parse a text.  A chart
+parser derives parse trees for a text by iteratively adding "edges"
+to a "chart."  Each edge represents a hypothesis about the tree
+structure for a subsequence of the text.  The chart is a
+"blackboard" for composing and combining these hypotheses.
+
+When a chart parser begins parsing a text, it creates a new (empty)
+chart, spanning the text.  It then incrementally adds new edges to the
+chart.  A set of "chart rules" specifies the conditions under which
+new edges should be added to the chart.  Once the chart reaches a
+stage where none of the chart rules adds any new edges, parsing is
+complete.
+
+Charts are encoded with the ``Chart`` class, and edges are encoded with
+the ``TreeEdge`` and ``LeafEdge`` classes.  The chart parser module
+defines three chart parsers:
+
+  - ``ChartParser`` is a simple and flexible chart parser.  Given a
+    set of chart rules, it will apply those rules to the chart until
+    no more edges are added.
+
+  - ``SteppingChartParser`` is a subclass of ``ChartParser`` that can
+    be used to step through the parsing process.
+"""
+
+import itertools
+import re
+import warnings
+from functools import total_ordering
+
+from nltk.grammar import PCFG, is_nonterminal, is_terminal
+from nltk.internals import raise_unorderable_types
+from nltk.parse.api import ParserI
+from nltk.tree import Tree
+from nltk.util import OrderedDict
+
+########################################################################
+##  Edges
+########################################################################
+
+
+@total_ordering
+class EdgeI:
+    """
+    A hypothesis about the structure of part of a sentence.
+    Each edge records the fact that a structure is (partially)
+    consistent with the sentence.  An edge contains:
+
+    - A span, indicating what part of the sentence is
+      consistent with the hypothesized structure.
+    - A left-hand side, specifying what kind of structure is
+      hypothesized.
+    - A right-hand side, specifying the contents of the
+      hypothesized structure.
+    - A dot position, indicating how much of the hypothesized
+      structure is consistent with the sentence.
+
+    Every edge is either complete or incomplete:
+
+    - An edge is complete if its structure is fully consistent
+      with the sentence.
+    - An edge is incomplete if its structure is partially
+      consistent with the sentence.  For every incomplete edge, the
+      span specifies a possible prefix for the edge's structure.
+
+    There are two kinds of edge:
+
+    - A ``TreeEdge`` records which trees have been found to
+      be (partially) consistent with the text.
+    - A ``LeafEdge`` records the tokens occurring in the text.
+
+    The ``EdgeI`` interface provides a common interface to both types
+    of edge, allowing chart parsers to treat them in a uniform manner.
+    """
+
+    def __init__(self):
+        if self.__class__ == EdgeI:
+            raise TypeError("Edge is an abstract interface")
+
+    # ////////////////////////////////////////////////////////////
+    # Span
+    # ////////////////////////////////////////////////////////////
+
+    def span(self):
+        """
+        Return a tuple ``(s, e)``, where ``tokens[s:e]`` is the
+        portion of the sentence that is consistent with this
+        edge's structure.
+
+        :rtype: tuple(int, int)
+        """
+        raise NotImplementedError()
+
+    def start(self):
+        """
+        Return the start index of this edge's span.
+
+        :rtype: int
+        """
+        raise NotImplementedError()
+
+    def end(self):
+        """
+        Return the end index of this edge's span.
+
+        :rtype: int
+        """
+        raise NotImplementedError()
+
+    def length(self):
+        """
+        Return the length of this edge's span.
+
+        :rtype: int
+        """
+        raise NotImplementedError()
+
+    # ////////////////////////////////////////////////////////////
+    # Left Hand Side
+    # ////////////////////////////////////////////////////////////
+
+    def lhs(self):
+        """
+        Return this edge's left-hand side, which specifies what kind
+        of structure is hypothesized by this edge.
+
+        :see: ``TreeEdge`` and ``LeafEdge`` for a description of
+            the left-hand side values for each edge type.
+        """
+        raise NotImplementedError()
+
+    # ////////////////////////////////////////////////////////////
+    # Right Hand Side
+    # ////////////////////////////////////////////////////////////
+
+    def rhs(self):
+        """
+        Return this edge's right-hand side, which specifies
+        the content of the structure hypothesized by this edge.
+
+        :see: ``TreeEdge`` and ``LeafEdge`` for a description of
+            the right-hand side values for each edge type.
+        """
+        raise NotImplementedError()
+
+    def dot(self):
+        """
+        Return this edge's dot position, which indicates how much of
+        the hypothesized structure is consistent with the
+        sentence.  In particular, ``self.rhs[:dot]`` is consistent
+        with ``tokens[self.start():self.end()]``.
+
+        :rtype: int
+        """
+        raise NotImplementedError()
+
+    def nextsym(self):
+        """
+        Return the element of this edge's right-hand side that
+        immediately follows its dot.
+
+        :rtype: Nonterminal or terminal or None
+        """
+        raise NotImplementedError()
+
+    def is_complete(self):
+        """
+        Return True if this edge's structure is fully consistent
+        with the text.
+
+        :rtype: bool
+        """
+        raise NotImplementedError()
+
+    def is_incomplete(self):
+        """
+        Return True if this edge's structure is partially consistent
+        with the text.
+
+        :rtype: bool
+        """
+        raise NotImplementedError()
+
+    # ////////////////////////////////////////////////////////////
+    # Comparisons & hashing
+    # ////////////////////////////////////////////////////////////
+
+    def __eq__(self, other):
+        return (
+            self.__class__ is other.__class__
+            and self._comparison_key == other._comparison_key
+        )
+
+    def __ne__(self, other):
+        return not self == other
+
+    def __lt__(self, other):
+        if not isinstance(other, EdgeI):
+            raise_unorderable_types("<", self, other)
+        if self.__class__ is other.__class__:
+            return self._comparison_key < other._comparison_key
+        else:
+            return self.__class__.__name__ < other.__class__.__name__
+
+    def __hash__(self):
+        try:
+            return self._hash
+        except AttributeError:
+            self._hash = hash(self._comparison_key)
+            return self._hash
+
+
+class TreeEdge(EdgeI):
+    """
+    An edge that records the fact that a tree is (partially)
+    consistent with the sentence.  A tree edge consists of:
+
+    - A span, indicating what part of the sentence is
+      consistent with the hypothesized tree.
+    - A left-hand side, specifying the hypothesized tree's node
+      value.
+    - A right-hand side, specifying the hypothesized tree's
+      children.  Each element of the right-hand side is either a
+      terminal, specifying a token with that terminal as its leaf
+      value; or a nonterminal, specifying a subtree with that
+      nonterminal's symbol as its node value.
+    - A dot position, indicating which children are consistent
+      with part of the sentence.  In particular, if ``dot`` is the
+      dot position, ``rhs`` is the right-hand size, ``(start,end)``
+      is the span, and ``sentence`` is the list of tokens in the
+      sentence, then ``tokens[start:end]`` can be spanned by the
+      children specified by ``rhs[:dot]``.
+
+    For more information about edges, see the ``EdgeI`` interface.
+    """
+
+    def __init__(self, span, lhs, rhs, dot=0):
+        """
+        Construct a new ``TreeEdge``.
+
+        :type span: tuple(int, int)
+        :param span: A tuple ``(s, e)``, where ``tokens[s:e]`` is the
+            portion of the sentence that is consistent with the new
+            edge's structure.
+        :type lhs: Nonterminal
+        :param lhs: The new edge's left-hand side, specifying the
+            hypothesized tree's node value.
+        :type rhs: list(Nonterminal and str)
+        :param rhs: The new edge's right-hand side, specifying the
+            hypothesized tree's children.
+        :type dot: int
+        :param dot: The position of the new edge's dot.  This position
+            specifies what prefix of the production's right hand side
+            is consistent with the text.  In particular, if
+            ``sentence`` is the list of tokens in the sentence, then
+            ``okens[span[0]:span[1]]`` can be spanned by the
+            children specified by ``rhs[:dot]``.
+        """
+        self._span = span
+        self._lhs = lhs
+        rhs = tuple(rhs)
+        self._rhs = rhs
+        self._dot = dot
+        self._comparison_key = (span, lhs, rhs, dot)
+
+    @staticmethod
+    def from_production(production, index):
+        """
+        Return a new ``TreeEdge`` formed from the given production.
+        The new edge's left-hand side and right-hand side will
+        be taken from ``production``; its span will be
+        ``(index,index)``; and its dot position will be ``0``.
+
+        :rtype: TreeEdge
+        """
+        return TreeEdge(
+            span=(index, index), lhs=production.lhs(), rhs=production.rhs(), dot=0
+        )
+
+    def move_dot_forward(self, new_end):
+        """
+        Return a new ``TreeEdge`` formed from this edge.
+        The new edge's dot position is increased by ``1``,
+        and its end index will be replaced by ``new_end``.
+
+        :param new_end: The new end index.
+        :type new_end: int
+        :rtype: TreeEdge
+        """
+        return TreeEdge(
+            span=(self._span[0], new_end),
+            lhs=self._lhs,
+            rhs=self._rhs,
+            dot=self._dot + 1,
+        )
+
+    # Accessors
+    def lhs(self):
+        return self._lhs
+
+    def span(self):
+        return self._span
+
+    def start(self):
+        return self._span[0]
+
+    def end(self):
+        return self._span[1]
+
+    def length(self):
+        return self._span[1] - self._span[0]
+
+    def rhs(self):
+        return self._rhs
+
+    def dot(self):
+        return self._dot
+
+    def is_complete(self):
+        return self._dot == len(self._rhs)
+
+    def is_incomplete(self):
+        return self._dot != len(self._rhs)
+
+    def nextsym(self):
+        if self._dot >= len(self._rhs):
+            return None
+        else:
+            return self._rhs[self._dot]
+
+    # String representation
+    def __str__(self):
+        str = f"[{self._span[0]}:{self._span[1]}] "
+        str += "%-2r ->" % (self._lhs,)
+
+        for i in range(len(self._rhs)):
+            if i == self._dot:
+                str += " *"
+            str += " %s" % repr(self._rhs[i])
+        if len(self._rhs) == self._dot:
+            str += " *"
+        return str
+
+    def __repr__(self):
+        return "[Edge: %s]" % self
+
+
+class LeafEdge(EdgeI):
+    """
+    An edge that records the fact that a leaf value is consistent with
+    a word in the sentence.  A leaf edge consists of:
+
+    - An index, indicating the position of the word.
+    - A leaf, specifying the word's content.
+
+    A leaf edge's left-hand side is its leaf value, and its right hand
+    side is ``()``.  Its span is ``[index, index+1]``, and its dot
+    position is ``0``.
+    """
+
+    def __init__(self, leaf, index):
+        """
+        Construct a new ``LeafEdge``.
+
+        :param leaf: The new edge's leaf value, specifying the word
+            that is recorded by this edge.
+        :param index: The new edge's index, specifying the position of
+            the word that is recorded by this edge.
+        """
+        self._leaf = leaf
+        self._index = index
+        self._comparison_key = (leaf, index)
+
+    # Accessors
+    def lhs(self):
+        return self._leaf
+
+    def span(self):
+        return (self._index, self._index + 1)
+
+    def start(self):
+        return self._index
+
+    def end(self):
+        return self._index + 1
+
+    def length(self):
+        return 1
+
+    def rhs(self):
+        return ()
+
+    def dot(self):
+        return 0
+
+    def is_complete(self):
+        return True
+
+    def is_incomplete(self):
+        return False
+
+    def nextsym(self):
+        return None
+
+    # String representations
+    def __str__(self):
+        return f"[{self._index}:{self._index + 1}] {repr(self._leaf)}"
+
+    def __repr__(self):
+        return "[Edge: %s]" % (self)
+
+
+########################################################################
+##  Chart
+########################################################################
+
+
+class Chart:
+    """
+    A blackboard for hypotheses about the syntactic constituents of a
+    sentence.  A chart contains a set of edges, and each edge encodes
+    a single hypothesis about the structure of some portion of the
+    sentence.
+
+    The ``select`` method can be used to select a specific collection
+    of edges.  For example ``chart.select(is_complete=True, start=0)``
+    yields all complete edges whose start indices are 0.  To ensure
+    the efficiency of these selection operations, ``Chart`` dynamically
+    creates and maintains an index for each set of attributes that
+    have been selected on.
+
+    In order to reconstruct the trees that are represented by an edge,
+    the chart associates each edge with a set of child pointer lists.
+    A child pointer list is a list of the edges that license an
+    edge's right-hand side.
+
+    :ivar _tokens: The sentence that the chart covers.
+    :ivar _num_leaves: The number of tokens.
+    :ivar _edges: A list of the edges in the chart
+    :ivar _edge_to_cpls: A dictionary mapping each edge to a set
+        of child pointer lists that are associated with that edge.
+    :ivar _indexes: A dictionary mapping tuples of edge attributes
+        to indices, where each index maps the corresponding edge
+        attribute values to lists of edges.
+    """
+
+    def __init__(self, tokens):
+        """
+        Construct a new chart. The chart is initialized with the
+        leaf edges corresponding to the terminal leaves.
+
+        :type tokens: list
+        :param tokens: The sentence that this chart will be used to parse.
+        """
+        # Record the sentence token and the sentence length.
+        self._tokens = tuple(tokens)
+        self._num_leaves = len(self._tokens)
+
+        # Initialise the chart.
+        self.initialize()
+
+    def initialize(self):
+        """
+        Clear the chart.
+        """
+        # A list of edges contained in this chart.
+        self._edges = []
+
+        # The set of child pointer lists associated with each edge.
+        self._edge_to_cpls = {}
+
+        # Indexes mapping attribute values to lists of edges
+        # (used by select()).
+        self._indexes = {}
+
+    # ////////////////////////////////////////////////////////////
+    # Sentence Access
+    # ////////////////////////////////////////////////////////////
+
+    def num_leaves(self):
+        """
+        Return the number of words in this chart's sentence.
+
+        :rtype: int
+        """
+        return self._num_leaves
+
+    def leaf(self, index):
+        """
+        Return the leaf value of the word at the given index.
+
+        :rtype: str
+        """
+        return self._tokens[index]
+
+    def leaves(self):
+        """
+        Return a list of the leaf values of each word in the
+        chart's sentence.
+
+        :rtype: list(str)
+        """
+        return self._tokens
+
+    # ////////////////////////////////////////////////////////////
+    # Edge access
+    # ////////////////////////////////////////////////////////////
+
+    def edges(self):
+        """
+        Return a list of all edges in this chart.  New edges
+        that are added to the chart after the call to edges()
+        will *not* be contained in this list.
+
+        :rtype: list(EdgeI)
+        :see: ``iteredges``, ``select``
+        """
+        return self._edges[:]
+
+    def iteredges(self):
+        """
+        Return an iterator over the edges in this chart.  It is
+        not guaranteed that new edges which are added to the
+        chart before the iterator is exhausted will also be generated.
+
+        :rtype: iter(EdgeI)
+        :see: ``edges``, ``select``
+        """
+        return iter(self._edges)
+
+    # Iterating over the chart yields its edges.
+    __iter__ = iteredges
+
+    def num_edges(self):
+        """
+        Return the number of edges contained in this chart.
+
+        :rtype: int
+        """
+        return len(self._edge_to_cpls)
+
+    def select(self, **restrictions):
+        """
+        Return an iterator over the edges in this chart.  Any
+        new edges that are added to the chart before the iterator
+        is exahusted will also be generated.  ``restrictions``
+        can be used to restrict the set of edges that will be
+        generated.
+
+        :param span: Only generate edges ``e`` where ``e.span()==span``
+        :param start: Only generate edges ``e`` where ``e.start()==start``
+        :param end: Only generate edges ``e`` where ``e.end()==end``
+        :param length: Only generate edges ``e`` where ``e.length()==length``
+        :param lhs: Only generate edges ``e`` where ``e.lhs()==lhs``
+        :param rhs: Only generate edges ``e`` where ``e.rhs()==rhs``
+        :param nextsym: Only generate edges ``e`` where
+            ``e.nextsym()==nextsym``
+        :param dot: Only generate edges ``e`` where ``e.dot()==dot``
+        :param is_complete: Only generate edges ``e`` where
+            ``e.is_complete()==is_complete``
+        :param is_incomplete: Only generate edges ``e`` where
+            ``e.is_incomplete()==is_incomplete``
+        :rtype: iter(EdgeI)
+        """
+        # If there are no restrictions, then return all edges.
+        if restrictions == {}:
+            return iter(self._edges)
+
+        # Find the index corresponding to the given restrictions.
+        restr_keys = sorted(restrictions.keys())
+        restr_keys = tuple(restr_keys)
+
+        # If it doesn't exist, then create it.
+        if restr_keys not in self._indexes:
+            self._add_index(restr_keys)
+
+        vals = tuple(restrictions[key] for key in restr_keys)
+        return iter(self._indexes[restr_keys].get(vals, []))
+
+    def _add_index(self, restr_keys):
+        """
+        A helper function for ``select``, which creates a new index for
+        a given set of attributes (aka restriction keys).
+        """
+        # Make sure it's a valid index.
+        for key in restr_keys:
+            if not hasattr(EdgeI, key):
+                raise ValueError("Bad restriction: %s" % key)
+
+        # Create the index.
+        index = self._indexes[restr_keys] = {}
+
+        # Add all existing edges to the index.
+        for edge in self._edges:
+            vals = tuple(getattr(edge, key)() for key in restr_keys)
+            index.setdefault(vals, []).append(edge)
+
+    def _register_with_indexes(self, edge):
+        """
+        A helper function for ``insert``, which registers the new
+        edge with all existing indexes.
+        """
+        for restr_keys, index in self._indexes.items():
+            vals = tuple(getattr(edge, key)() for key in restr_keys)
+            index.setdefault(vals, []).append(edge)
+
+    # ////////////////////////////////////////////////////////////
+    # Edge Insertion
+    # ////////////////////////////////////////////////////////////
+
+    def insert_with_backpointer(self, new_edge, previous_edge, child_edge):
+        """
+        Add a new edge to the chart, using a pointer to the previous edge.
+        """
+        cpls = self.child_pointer_lists(previous_edge)
+        new_cpls = [cpl + (child_edge,) for cpl in cpls]
+        return self.insert(new_edge, *new_cpls)
+
+    def insert(self, edge, *child_pointer_lists):
+        """
+        Add a new edge to the chart, and return True if this operation
+        modified the chart.  In particular, return true iff the chart
+        did not already contain ``edge``, or if it did not already associate
+        ``child_pointer_lists`` with ``edge``.
+
+        :type edge: EdgeI
+        :param edge: The new edge
+        :type child_pointer_lists: sequence of tuple(EdgeI)
+        :param child_pointer_lists: A sequence of lists of the edges that
+            were used to form this edge.  This list is used to reconstruct
+            the trees (or partial trees) that are associated with ``edge``.
+        :rtype: bool
+        """
+        # Is it a new edge?
+        if edge not in self._edge_to_cpls:
+            # Add it to the list of edges.
+            self._append_edge(edge)
+            # Register with indexes.
+            self._register_with_indexes(edge)
+
+        # Get the set of child pointer lists for this edge.
+        cpls = self._edge_to_cpls.setdefault(edge, OrderedDict())
+        chart_was_modified = False
+        for child_pointer_list in child_pointer_lists:
+            child_pointer_list = tuple(child_pointer_list)
+            if child_pointer_list not in cpls:
+                # It's a new CPL; register it, and return true.
+                cpls[child_pointer_list] = True
+                chart_was_modified = True
+        return chart_was_modified
+
+    def _append_edge(self, edge):
+        self._edges.append(edge)
+
+    # ////////////////////////////////////////////////////////////
+    # Tree extraction & child pointer lists
+    # ////////////////////////////////////////////////////////////
+
+    def parses(self, root, tree_class=Tree):
+        """
+        Return an iterator of the complete tree structures that span
+        the entire chart, and whose root node is ``root``.
+        """
+        for edge in self.select(start=0, end=self._num_leaves, lhs=root):
+            yield from self.trees(edge, tree_class=tree_class, complete=True)
+
+    def trees(self, edge, tree_class=Tree, complete=False):
+        """
+        Return an iterator of the tree structures that are associated
+        with ``edge``.
+
+        If ``edge`` is incomplete, then the unexpanded children will be
+        encoded as childless subtrees, whose node value is the
+        corresponding terminal or nonterminal.
+
+        :rtype: list(Tree)
+        :note: If two trees share a common subtree, then the same
+            Tree may be used to encode that subtree in
+            both trees.  If you need to eliminate this subtree
+            sharing, then create a deep copy of each tree.
+        """
+        return iter(self._trees(edge, complete, memo={}, tree_class=tree_class))
+
+    def _trees(self, edge, complete, memo, tree_class):
+        """
+        A helper function for ``trees``.
+
+        :param memo: A dictionary used to record the trees that we've
+            generated for each edge, so that when we see an edge more
+            than once, we can reuse the same trees.
+        """
+        # If we've seen this edge before, then reuse our old answer.
+        if edge in memo:
+            return memo[edge]
+
+        # when we're reading trees off the chart, don't use incomplete edges
+        if complete and edge.is_incomplete():
+            return []
+
+        # Leaf edges.
+        if isinstance(edge, LeafEdge):
+            leaf = self._tokens[edge.start()]
+            memo[edge] = [leaf]
+            return [leaf]
+
+        # Until we're done computing the trees for edge, set
+        # memo[edge] to be empty.  This has the effect of filtering
+        # out any cyclic trees (i.e., trees that contain themselves as
+        # descendants), because if we reach this edge via a cycle,
+        # then it will appear that the edge doesn't generate any trees.
+        memo[edge] = []
+        trees = []
+        lhs = edge.lhs().symbol()
+
+        # Each child pointer list can be used to form trees.
+        for cpl in self.child_pointer_lists(edge):
+            # Get the set of child choices for each child pointer.
+            # child_choices[i] is the set of choices for the tree's
+            # ith child.
+            child_choices = [self._trees(cp, complete, memo, tree_class) for cp in cpl]
+
+            # For each combination of children, add a tree.
+            for children in itertools.product(*child_choices):
+                trees.append(tree_class(lhs, children))
+
+        # If the edge is incomplete, then extend it with "partial trees":
+        if edge.is_incomplete():
+            unexpanded = [tree_class(elt, []) for elt in edge.rhs()[edge.dot() :]]
+            for tree in trees:
+                tree.extend(unexpanded)
+
+        # Update the memoization dictionary.
+        memo[edge] = trees
+
+        # Return the list of trees.
+        return trees
+
+    def child_pointer_lists(self, edge):
+        """
+        Return the set of child pointer lists for the given edge.
+        Each child pointer list is a list of edges that have
+        been used to form this edge.
+
+        :rtype: list(list(EdgeI))
+        """
+        # Make a copy, in case they modify it.
+        return self._edge_to_cpls.get(edge, {}).keys()
+
+    # ////////////////////////////////////////////////////////////
+    # Display
+    # ////////////////////////////////////////////////////////////
+    def pretty_format_edge(self, edge, width=None):
+        """
+        Return a pretty-printed string representation of a given edge
+        in this chart.
+
+        :rtype: str
+        :param width: The number of characters allotted to each
+            index in the sentence.
+        """
+        if width is None:
+            width = 50 // (self.num_leaves() + 1)
+        (start, end) = (edge.start(), edge.end())
+
+        str = "|" + ("." + " " * (width - 1)) * start
+
+        # Zero-width edges are "#" if complete, ">" if incomplete
+        if start == end:
+            if edge.is_complete():
+                str += "#"
+            else:
+                str += ">"
+
+        # Spanning complete edges are "[===]"; Other edges are
+        # "[---]" if complete, "[--->" if incomplete
+        elif edge.is_complete() and edge.span() == (0, self._num_leaves):
+            str += "[" + ("=" * width) * (end - start - 1) + "=" * (width - 1) + "]"
+        elif edge.is_complete():
+            str += "[" + ("-" * width) * (end - start - 1) + "-" * (width - 1) + "]"
+        else:
+            str += "[" + ("-" * width) * (end - start - 1) + "-" * (width - 1) + ">"
+
+        str += (" " * (width - 1) + ".") * (self._num_leaves - end)
+        return str + "| %s" % edge
+
+    def pretty_format_leaves(self, width=None):
+        """
+        Return a pretty-printed string representation of this
+        chart's leaves.  This string can be used as a header
+        for calls to ``pretty_format_edge``.
+        """
+        if width is None:
+            width = 50 // (self.num_leaves() + 1)
+
+        if self._tokens is not None and width > 1:
+            header = "|."
+            for tok in self._tokens:
+                header += tok[: width - 1].center(width - 1) + "."
+            header += "|"
+        else:
+            header = ""
+
+        return header
+
+    def pretty_format(self, width=None):
+        """
+        Return a pretty-printed string representation of this chart.
+
+        :param width: The number of characters allotted to each
+            index in the sentence.
+        :rtype: str
+        """
+        if width is None:
+            width = 50 // (self.num_leaves() + 1)
+        # sort edges: primary key=length, secondary key=start index.
+        # (and filter out the token edges)
+        edges = sorted((e.length(), e.start(), e) for e in self)
+        edges = [e for (_, _, e) in edges]
+
+        return (
+            self.pretty_format_leaves(width)
+            + "\n"
+            + "\n".join(self.pretty_format_edge(edge, width) for edge in edges)
+        )
+
+    # ////////////////////////////////////////////////////////////
+    # Display: Dot (AT&T Graphviz)
+    # ////////////////////////////////////////////////////////////
+
+    def dot_digraph(self):
+        # Header
+        s = "digraph nltk_chart {\n"
+        # s += '  size="5,5";\n'
+        s += "  rankdir=LR;\n"
+        s += "  node [height=0.1,width=0.1];\n"
+        s += '  node [style=filled, color="lightgray"];\n'
+
+        # Set up the nodes
+        for y in range(self.num_edges(), -1, -1):
+            if y == 0:
+                s += '  node [style=filled, color="black"];\n'
+            for x in range(self.num_leaves() + 1):
+                if y == 0 or (
+                    x <= self._edges[y - 1].start() or x >= self._edges[y - 1].end()
+                ):
+                    s += '  %04d.%04d [label=""];\n' % (x, y)
+
+        # Add a spacer
+        s += "  x [style=invis]; x->0000.0000 [style=invis];\n"
+
+        # Declare ranks.
+        for x in range(self.num_leaves() + 1):
+            s += "  {rank=same;"
+            for y in range(self.num_edges() + 1):
+                if y == 0 or (
+                    x <= self._edges[y - 1].start() or x >= self._edges[y - 1].end()
+                ):
+                    s += " %04d.%04d" % (x, y)
+            s += "}\n"
+
+        # Add the leaves
+        s += "  edge [style=invis, weight=100];\n"
+        s += "  node [shape=plaintext]\n"
+        s += "  0000.0000"
+        for x in range(self.num_leaves()):
+            s += "->%s->%04d.0000" % (self.leaf(x), x + 1)
+        s += ";\n\n"
+
+        # Add the edges
+        s += "  edge [style=solid, weight=1];\n"
+        for y, edge in enumerate(self):
+            for x in range(edge.start()):
+                s += '  %04d.%04d -> %04d.%04d [style="invis"];\n' % (
+                    x,
+                    y + 1,
+                    x + 1,
+                    y + 1,
+                )
+            s += '  %04d.%04d -> %04d.%04d [label="%s"];\n' % (
+                edge.start(),
+                y + 1,
+                edge.end(),
+                y + 1,
+                edge,
+            )
+            for x in range(edge.end(), self.num_leaves()):
+                s += '  %04d.%04d -> %04d.%04d [style="invis"];\n' % (
+                    x,
+                    y + 1,
+                    x + 1,
+                    y + 1,
+                )
+        s += "}\n"
+        return s
+
+
+########################################################################
+##  Chart Rules
+########################################################################
+
+
+class ChartRuleI:
+    """
+    A rule that specifies what new edges are licensed by any given set
+    of existing edges.  Each chart rule expects a fixed number of
+    edges, as indicated by the class variable ``NUM_EDGES``.  In
+    particular:
+
+    - A chart rule with ``NUM_EDGES=0`` specifies what new edges are
+      licensed, regardless of existing edges.
+    - A chart rule with ``NUM_EDGES=1`` specifies what new edges are
+      licensed by a single existing edge.
+    - A chart rule with ``NUM_EDGES=2`` specifies what new edges are
+      licensed by a pair of existing edges.
+
+    :type NUM_EDGES: int
+    :cvar NUM_EDGES: The number of existing edges that this rule uses
+        to license new edges.  Typically, this number ranges from zero
+        to two.
+    """
+
+    def apply(self, chart, grammar, *edges):
+        """
+        Return a generator that will add edges licensed by this rule
+        and the given edges to the chart, one at a time.  Each
+        time the generator is resumed, it will either add a new
+        edge and yield that edge; or return.
+
+        :type edges: list(EdgeI)
+        :param edges: A set of existing edges.  The number of edges
+            that should be passed to ``apply()`` is specified by the
+            ``NUM_EDGES`` class variable.
+        :rtype: iter(EdgeI)
+        """
+        raise NotImplementedError()
+
+    def apply_everywhere(self, chart, grammar):
+        """
+        Return a generator that will add all edges licensed by
+        this rule, given the edges that are currently in the
+        chart, one at a time.  Each time the generator is resumed,
+        it will either add a new edge and yield that edge; or return.
+
+        :rtype: iter(EdgeI)
+        """
+        raise NotImplementedError()
+
+
+class AbstractChartRule(ChartRuleI):
+    """
+    An abstract base class for chart rules.  ``AbstractChartRule``
+    provides:
+
+    - A default implementation for ``apply``.
+    - A default implementation for ``apply_everywhere``,
+      (Currently, this implementation assumes that ``NUM_EDGES <= 3``.)
+    - A default implementation for ``__str__``, which returns a
+      name based on the rule's class name.
+    """
+
+    # Subclasses must define apply.
+    def apply(self, chart, grammar, *edges):
+        raise NotImplementedError()
+
+    # Default: loop through the given number of edges, and call
+    # self.apply() for each set of edges.
+    def apply_everywhere(self, chart, grammar):
+        if self.NUM_EDGES == 0:
+            yield from self.apply(chart, grammar)
+
+        elif self.NUM_EDGES == 1:
+            for e1 in chart:
+                yield from self.apply(chart, grammar, e1)
+
+        elif self.NUM_EDGES == 2:
+            for e1 in chart:
+                for e2 in chart:
+                    yield from self.apply(chart, grammar, e1, e2)
+
+        elif self.NUM_EDGES == 3:
+            for e1 in chart:
+                for e2 in chart:
+                    for e3 in chart:
+                        yield from self.apply(chart, grammar, e1, e2, e3)
+
+        else:
+            raise AssertionError("NUM_EDGES>3 is not currently supported")
+
+    # Default: return a name based on the class name.
+    def __str__(self):
+        # Add spaces between InitialCapsWords.
+        return re.sub("([a-z])([A-Z])", r"\1 \2", self.__class__.__name__)
+
+
+# ////////////////////////////////////////////////////////////
+# Fundamental Rule
+# ////////////////////////////////////////////////////////////
+
+
+class FundamentalRule(AbstractChartRule):
+    r"""
+    A rule that joins two adjacent edges to form a single combined
+    edge.  In particular, this rule specifies that any pair of edges
+
+    - ``[A -> alpha \* B beta][i:j]``
+    - ``[B -> gamma \*][j:k]``
+
+    licenses the edge:
+
+    - ``[A -> alpha B * beta][i:j]``
+    """
+
+    NUM_EDGES = 2
+
+    def apply(self, chart, grammar, left_edge, right_edge):
+        # Make sure the rule is applicable.
+        if not (
+            left_edge.is_incomplete()
+            and right_edge.is_complete()
+            and left_edge.end() == right_edge.start()
+            and left_edge.nextsym() == right_edge.lhs()
+        ):
+            return
+
+        # Construct the new edge.
+        new_edge = left_edge.move_dot_forward(right_edge.end())
+
+        # Insert it into the chart.
+        if chart.insert_with_backpointer(new_edge, left_edge, right_edge):
+            yield new_edge
+
+
+class SingleEdgeFundamentalRule(FundamentalRule):
+    r"""
+    A rule that joins a given edge with adjacent edges in the chart,
+    to form combined edges.  In particular, this rule specifies that
+    either of the edges:
+
+    - ``[A -> alpha \* B beta][i:j]``
+    - ``[B -> gamma \*][j:k]``
+
+    licenses the edge:
+
+    - ``[A -> alpha B * beta][i:j]``
+
+    if the other edge is already in the chart.
+
+    :note: This is basically ``FundamentalRule``, with one edge left
+        unspecified.
+    """
+
+    NUM_EDGES = 1
+
+    def apply(self, chart, grammar, edge):
+        if edge.is_incomplete():
+            yield from self._apply_incomplete(chart, grammar, edge)
+        else:
+            yield from self._apply_complete(chart, grammar, edge)
+
+    def _apply_complete(self, chart, grammar, right_edge):
+        for left_edge in chart.select(
+            end=right_edge.start(), is_complete=False, nextsym=right_edge.lhs()
+        ):
+            new_edge = left_edge.move_dot_forward(right_edge.end())
+            if chart.insert_with_backpointer(new_edge, left_edge, right_edge):
+                yield new_edge
+
+    def _apply_incomplete(self, chart, grammar, left_edge):
+        for right_edge in chart.select(
+            start=left_edge.end(), is_complete=True, lhs=left_edge.nextsym()
+        ):
+            new_edge = left_edge.move_dot_forward(right_edge.end())
+            if chart.insert_with_backpointer(new_edge, left_edge, right_edge):
+                yield new_edge
+
+
+# ////////////////////////////////////////////////////////////
+# Inserting Terminal Leafs
+# ////////////////////////////////////////////////////////////
+
+
+class LeafInitRule(AbstractChartRule):
+    NUM_EDGES = 0
+
+    def apply(self, chart, grammar):
+        for index in range(chart.num_leaves()):
+            new_edge = LeafEdge(chart.leaf(index), index)
+            if chart.insert(new_edge, ()):
+                yield new_edge
+
+
+# ////////////////////////////////////////////////////////////
+# Top-Down Prediction
+# ////////////////////////////////////////////////////////////
+
+
+class TopDownInitRule(AbstractChartRule):
+    r"""
+    A rule licensing edges corresponding to the grammar productions for
+    the grammar's start symbol.  In particular, this rule specifies that
+    ``[S -> \* alpha][0:i]`` is licensed for each grammar production
+    ``S -> alpha``, where ``S`` is the grammar's start symbol.
+    """
+
+    NUM_EDGES = 0
+
+    def apply(self, chart, grammar):
+        for prod in grammar.productions(lhs=grammar.start()):
+            new_edge = TreeEdge.from_production(prod, 0)
+            if chart.insert(new_edge, ()):
+                yield new_edge
+
+
+class TopDownPredictRule(AbstractChartRule):
+    r"""
+    A rule licensing edges corresponding to the grammar productions
+    for the nonterminal following an incomplete edge's dot.  In
+    particular, this rule specifies that
+    ``[A -> alpha \* B beta][i:j]`` licenses the edge
+    ``[B -> \* gamma][j:j]`` for each grammar production ``B -> gamma``.
+
+    :note: This rule corresponds to the Predictor Rule in Earley parsing.
+    """
+
+    NUM_EDGES = 1
+
+    def apply(self, chart, grammar, edge):
+        if edge.is_complete():
+            return
+        for prod in grammar.productions(lhs=edge.nextsym()):
+            new_edge = TreeEdge.from_production(prod, edge.end())
+            if chart.insert(new_edge, ()):
+                yield new_edge
+
+
+class CachedTopDownPredictRule(TopDownPredictRule):
+    r"""
+    A cached version of ``TopDownPredictRule``.  After the first time
+    this rule is applied to an edge with a given ``end`` and ``next``,
+    it will not generate any more edges for edges with that ``end`` and
+    ``next``.
+
+    If ``chart`` or ``grammar`` are changed, then the cache is flushed.
+    """
+
+    def __init__(self):
+        TopDownPredictRule.__init__(self)
+        self._done = {}
+
+    def apply(self, chart, grammar, edge):
+        if edge.is_complete():
+            return
+        nextsym, index = edge.nextsym(), edge.end()
+        if not is_nonterminal(nextsym):
+            return
+
+        # If we've already applied this rule to an edge with the same
+        # next & end, and the chart & grammar have not changed, then
+        # just return (no new edges to add).
+        done = self._done.get((nextsym, index), (None, None))
+        if done[0] is chart and done[1] is grammar:
+            return
+
+        # Add all the edges indicated by the top down expand rule.
+        for prod in grammar.productions(lhs=nextsym):
+            # If the left corner in the predicted production is
+            # leaf, it must match with the input.
+            if prod.rhs():
+                first = prod.rhs()[0]
+                if is_terminal(first):
+                    if index >= chart.num_leaves() or first != chart.leaf(index):
+                        continue
+
+            new_edge = TreeEdge.from_production(prod, index)
+            if chart.insert(new_edge, ()):
+                yield new_edge
+
+        # Record the fact that we've applied this rule.
+        self._done[nextsym, index] = (chart, grammar)
+
+
+# ////////////////////////////////////////////////////////////
+# Bottom-Up Prediction
+# ////////////////////////////////////////////////////////////
+
+
+class BottomUpPredictRule(AbstractChartRule):
+    r"""
+    A rule licensing any edge corresponding to a production whose
+    right-hand side begins with a complete edge's left-hand side.  In
+    particular, this rule specifies that ``[A -> alpha \*]`` licenses
+    the edge ``[B -> \* A beta]`` for each grammar production ``B -> A beta``.
+    """
+
+    NUM_EDGES = 1
+
+    def apply(self, chart, grammar, edge):
+        if edge.is_incomplete():
+            return
+        for prod in grammar.productions(rhs=edge.lhs()):
+            new_edge = TreeEdge.from_production(prod, edge.start())
+            if chart.insert(new_edge, ()):
+                yield new_edge
+
+
+class BottomUpPredictCombineRule(BottomUpPredictRule):
+    r"""
+    A rule licensing any edge corresponding to a production whose
+    right-hand side begins with a complete edge's left-hand side.  In
+    particular, this rule specifies that ``[A -> alpha \*]``
+    licenses the edge ``[B -> A \* beta]`` for each grammar
+    production ``B -> A beta``.
+
+    :note: This is like ``BottomUpPredictRule``, but it also applies
+        the ``FundamentalRule`` to the resulting edge.
+    """
+
+    NUM_EDGES = 1
+
+    def apply(self, chart, grammar, edge):
+        if edge.is_incomplete():
+            return
+        for prod in grammar.productions(rhs=edge.lhs()):
+            new_edge = TreeEdge(edge.span(), prod.lhs(), prod.rhs(), 1)
+            if chart.insert(new_edge, (edge,)):
+                yield new_edge
+
+
+class EmptyPredictRule(AbstractChartRule):
+    """
+    A rule that inserts all empty productions as passive edges,
+    in every position in the chart.
+    """
+
+    NUM_EDGES = 0
+
+    def apply(self, chart, grammar):
+        for prod in grammar.productions(empty=True):
+            for index in range(chart.num_leaves() + 1):
+                new_edge = TreeEdge.from_production(prod, index)
+                if chart.insert(new_edge, ()):
+                    yield new_edge
+
+
+########################################################################
+##  Filtered Bottom Up
+########################################################################
+
+
+class FilteredSingleEdgeFundamentalRule(SingleEdgeFundamentalRule):
+    def _apply_complete(self, chart, grammar, right_edge):
+        end = right_edge.end()
+        nexttoken = end < chart.num_leaves() and chart.leaf(end)
+        for left_edge in chart.select(
+            end=right_edge.start(), is_complete=False, nextsym=right_edge.lhs()
+        ):
+            if _bottomup_filter(grammar, nexttoken, left_edge.rhs(), left_edge.dot()):
+                new_edge = left_edge.move_dot_forward(right_edge.end())
+                if chart.insert_with_backpointer(new_edge, left_edge, right_edge):
+                    yield new_edge
+
+    def _apply_incomplete(self, chart, grammar, left_edge):
+        for right_edge in chart.select(
+            start=left_edge.end(), is_complete=True, lhs=left_edge.nextsym()
+        ):
+            end = right_edge.end()
+            nexttoken = end < chart.num_leaves() and chart.leaf(end)
+            if _bottomup_filter(grammar, nexttoken, left_edge.rhs(), left_edge.dot()):
+                new_edge = left_edge.move_dot_forward(right_edge.end())
+                if chart.insert_with_backpointer(new_edge, left_edge, right_edge):
+                    yield new_edge
+
+
+class FilteredBottomUpPredictCombineRule(BottomUpPredictCombineRule):
+    def apply(self, chart, grammar, edge):
+        if edge.is_incomplete():
+            return
+
+        end = edge.end()
+        nexttoken = end < chart.num_leaves() and chart.leaf(end)
+        for prod in grammar.productions(rhs=edge.lhs()):
+            if _bottomup_filter(grammar, nexttoken, prod.rhs()):
+                new_edge = TreeEdge(edge.span(), prod.lhs(), prod.rhs(), 1)
+                if chart.insert(new_edge, (edge,)):
+                    yield new_edge
+
+
+def _bottomup_filter(grammar, nexttoken, rhs, dot=0):
+    if len(rhs) <= dot + 1:
+        return True
+    _next = rhs[dot + 1]
+    if is_terminal(_next):
+        return nexttoken == _next
+    else:
+        return grammar.is_leftcorner(_next, nexttoken)
+
+
+########################################################################
+##  Generic Chart Parser
+########################################################################
+
+TD_STRATEGY = [
+    LeafInitRule(),
+    TopDownInitRule(),
+    CachedTopDownPredictRule(),
+    SingleEdgeFundamentalRule(),
+]
+BU_STRATEGY = [
+    LeafInitRule(),
+    EmptyPredictRule(),
+    BottomUpPredictRule(),
+    SingleEdgeFundamentalRule(),
+]
+BU_LC_STRATEGY = [
+    LeafInitRule(),
+    EmptyPredictRule(),
+    BottomUpPredictCombineRule(),
+    SingleEdgeFundamentalRule(),
+]
+
+LC_STRATEGY = [
+    LeafInitRule(),
+    FilteredBottomUpPredictCombineRule(),
+    FilteredSingleEdgeFundamentalRule(),
+]
+
+
+class ChartParser(ParserI):
+    """
+    A generic chart parser.  A "strategy", or list of
+    ``ChartRuleI`` instances, is used to decide what edges to add to
+    the chart.  In particular, ``ChartParser`` uses the following
+    algorithm to parse texts:
+
+    | Until no new edges are added:
+    |   For each *rule* in *strategy*:
+    |     Apply *rule* to any applicable edges in the chart.
+    | Return any complete parses in the chart
+    """
+
+    def __init__(
+        self,
+        grammar,
+        strategy=BU_LC_STRATEGY,
+        trace=0,
+        trace_chart_width=50,
+        use_agenda=True,
+        chart_class=Chart,
+    ):
+        """
+        Create a new chart parser, that uses ``grammar`` to parse
+        texts.
+
+        :type grammar: CFG
+        :param grammar: The grammar used to parse texts.
+        :type strategy: list(ChartRuleI)
+        :param strategy: A list of rules that should be used to decide
+            what edges to add to the chart (top-down strategy by default).
+        :type trace: int
+        :param trace: The level of tracing that should be used when
+            parsing a text.  ``0`` will generate no tracing output;
+            and higher numbers will produce more verbose tracing
+            output.
+        :type trace_chart_width: int
+        :param trace_chart_width: The default total width reserved for
+            the chart in trace output.  The remainder of each line will
+            be used to display edges.
+        :type use_agenda: bool
+        :param use_agenda: Use an optimized agenda-based algorithm,
+            if possible.
+        :param chart_class: The class that should be used to create
+            the parse charts.
+        """
+        self._grammar = grammar
+        self._strategy = strategy
+        self._trace = trace
+        self._trace_chart_width = trace_chart_width
+        # If the strategy only consists of axioms (NUM_EDGES==0) and
+        # inference rules (NUM_EDGES==1), we can use an agenda-based algorithm:
+        self._use_agenda = use_agenda
+        self._chart_class = chart_class
+
+        self._axioms = []
+        self._inference_rules = []
+        for rule in strategy:
+            if rule.NUM_EDGES == 0:
+                self._axioms.append(rule)
+            elif rule.NUM_EDGES == 1:
+                self._inference_rules.append(rule)
+            else:
+                self._use_agenda = False
+
+    def grammar(self):
+        return self._grammar
+
+    def _trace_new_edges(self, chart, rule, new_edges, trace, edge_width):
+        if not trace:
+            return
+        print_rule_header = trace > 1
+        for edge in new_edges:
+            if print_rule_header:
+                print("%s:" % rule)
+                print_rule_header = False
+            print(chart.pretty_format_edge(edge, edge_width))
+
+    def chart_parse(self, tokens, trace=None):
+        """
+        Return the final parse ``Chart`` from which all possible
+        parse trees can be extracted.
+
+        :param tokens: The sentence to be parsed
+        :type tokens: list(str)
+        :rtype: Chart
+        """
+        if trace is None:
+            trace = self._trace
+        trace_new_edges = self._trace_new_edges
+
+        tokens = list(tokens)
+        self._grammar.check_coverage(tokens)
+        chart = self._chart_class(tokens)
+        grammar = self._grammar
+
+        # Width, for printing trace edges.
+        trace_edge_width = self._trace_chart_width // (chart.num_leaves() + 1)
+        if trace:
+            print(chart.pretty_format_leaves(trace_edge_width))
+
+        if self._use_agenda:
+            # Use an agenda-based algorithm.
+            for axiom in self._axioms:
+                new_edges = list(axiom.apply(chart, grammar))
+                trace_new_edges(chart, axiom, new_edges, trace, trace_edge_width)
+
+            inference_rules = self._inference_rules
+            agenda = chart.edges()
+            # We reverse the initial agenda, since it is a stack
+            # but chart.edges() functions as a queue.
+            agenda.reverse()
+            while agenda:
+                edge = agenda.pop()
+                for rule in inference_rules:
+                    new_edges = list(rule.apply(chart, grammar, edge))
+                    if trace:
+                        trace_new_edges(chart, rule, new_edges, trace, trace_edge_width)
+                    agenda += new_edges
+
+        else:
+            # Do not use an agenda-based algorithm.
+            edges_added = True
+            while edges_added:
+                edges_added = False
+                for rule in self._strategy:
+                    new_edges = list(rule.apply_everywhere(chart, grammar))
+                    edges_added = len(new_edges)
+                    trace_new_edges(chart, rule, new_edges, trace, trace_edge_width)
+
+        # Return the final chart.
+        return chart
+
+    def parse(self, tokens, tree_class=Tree):
+        chart = self.chart_parse(tokens)
+        return iter(chart.parses(self._grammar.start(), tree_class=tree_class))
+
+
+class TopDownChartParser(ChartParser):
+    """
+    A ``ChartParser`` using a top-down parsing strategy.
+    See ``ChartParser`` for more information.
+    """
+
+    def __init__(self, grammar, **parser_args):
+        ChartParser.__init__(self, grammar, TD_STRATEGY, **parser_args)
+
+
+class BottomUpChartParser(ChartParser):
+    """
+    A ``ChartParser`` using a bottom-up parsing strategy.
+    See ``ChartParser`` for more information.
+    """
+
+    def __init__(self, grammar, **parser_args):
+        if isinstance(grammar, PCFG):
+            warnings.warn(
+                "BottomUpChartParser only works for CFG, "
+                "use BottomUpProbabilisticChartParser instead",
+                category=DeprecationWarning,
+            )
+        ChartParser.__init__(self, grammar, BU_STRATEGY, **parser_args)
+
+
+class BottomUpLeftCornerChartParser(ChartParser):
+    """
+    A ``ChartParser`` using a bottom-up left-corner parsing strategy.
+    This strategy is often more efficient than standard bottom-up.
+    See ``ChartParser`` for more information.
+    """
+
+    def __init__(self, grammar, **parser_args):
+        ChartParser.__init__(self, grammar, BU_LC_STRATEGY, **parser_args)
+
+
+class LeftCornerChartParser(ChartParser):
+    def __init__(self, grammar, **parser_args):
+        if not grammar.is_nonempty():
+            raise ValueError(
+                "LeftCornerParser only works for grammars " "without empty productions."
+            )
+        ChartParser.__init__(self, grammar, LC_STRATEGY, **parser_args)
+
+
+########################################################################
+##  Stepping Chart Parser
+########################################################################
+
+
+class SteppingChartParser(ChartParser):
+    """
+    A ``ChartParser`` that allows you to step through the parsing
+    process, adding a single edge at a time.  It also allows you to
+    change the parser's strategy or grammar midway through parsing a
+    text.
+
+    The ``initialize`` method is used to start parsing a text.  ``step``
+    adds a single edge to the chart.  ``set_strategy`` changes the
+    strategy used by the chart parser.  ``parses`` returns the set of
+    parses that has been found by the chart parser.
+
+    :ivar _restart: Records whether the parser's strategy, grammar,
+        or chart has been changed.  If so, then ``step`` must restart
+        the parsing algorithm.
+    """
+
+    def __init__(self, grammar, strategy=[], trace=0):
+        self._chart = None
+        self._current_chartrule = None
+        self._restart = False
+        ChartParser.__init__(self, grammar, strategy, trace)
+
+    # ////////////////////////////////////////////////////////////
+    # Initialization
+    # ////////////////////////////////////////////////////////////
+
+    def initialize(self, tokens):
+        "Begin parsing the given tokens."
+        self._chart = Chart(list(tokens))
+        self._restart = True
+
+    # ////////////////////////////////////////////////////////////
+    # Stepping
+    # ////////////////////////////////////////////////////////////
+
+    def step(self):
+        """
+        Return a generator that adds edges to the chart, one at a
+        time.  Each time the generator is resumed, it adds a single
+        edge and yields that edge.  If no more edges can be added,
+        then it yields None.
+
+        If the parser's strategy, grammar, or chart is changed, then
+        the generator will continue adding edges using the new
+        strategy, grammar, or chart.
+
+        Note that this generator never terminates, since the grammar
+        or strategy might be changed to values that would add new
+        edges.  Instead, it yields None when no more edges can be
+        added with the current strategy and grammar.
+        """
+        if self._chart is None:
+            raise ValueError("Parser must be initialized first")
+        while True:
+            self._restart = False
+            w = 50 // (self._chart.num_leaves() + 1)
+
+            for e in self._parse():
+                if self._trace > 1:
+                    print(self._current_chartrule)
+                if self._trace > 0:
+                    print(self._chart.pretty_format_edge(e, w))
+                yield e
+                if self._restart:
+                    break
+            else:
+                yield None  # No more edges.
+
+    def _parse(self):
+        """
+        A generator that implements the actual parsing algorithm.
+        ``step`` iterates through this generator, and restarts it
+        whenever the parser's strategy, grammar, or chart is modified.
+        """
+        chart = self._chart
+        grammar = self._grammar
+        edges_added = 1
+        while edges_added > 0:
+            edges_added = 0
+            for rule in self._strategy:
+                self._current_chartrule = rule
+                for e in rule.apply_everywhere(chart, grammar):
+                    edges_added += 1
+                    yield e
+
+    # ////////////////////////////////////////////////////////////
+    # Accessors
+    # ////////////////////////////////////////////////////////////
+
+    def strategy(self):
+        "Return the strategy used by this parser."
+        return self._strategy
+
+    def grammar(self):
+        "Return the grammar used by this parser."
+        return self._grammar
+
+    def chart(self):
+        "Return the chart that is used by this parser."
+        return self._chart
+
+    def current_chartrule(self):
+        "Return the chart rule used to generate the most recent edge."
+        return self._current_chartrule
+
+    def parses(self, tree_class=Tree):
+        "Return the parse trees currently contained in the chart."
+        return self._chart.parses(self._grammar.start(), tree_class)
+
+    # ////////////////////////////////////////////////////////////
+    # Parser modification
+    # ////////////////////////////////////////////////////////////
+
+    def set_strategy(self, strategy):
+        """
+        Change the strategy that the parser uses to decide which edges
+        to add to the chart.
+
+        :type strategy: list(ChartRuleI)
+        :param strategy: A list of rules that should be used to decide
+            what edges to add to the chart.
+        """
+        if strategy == self._strategy:
+            return
+        self._strategy = strategy[:]  # Make a copy.
+        self._restart = True
+
+    def set_grammar(self, grammar):
+        "Change the grammar used by the parser."
+        if grammar is self._grammar:
+            return
+        self._grammar = grammar
+        self._restart = True
+
+    def set_chart(self, chart):
+        "Load a given chart into the chart parser."
+        if chart is self._chart:
+            return
+        self._chart = chart
+        self._restart = True
+
+    # ////////////////////////////////////////////////////////////
+    # Standard parser methods
+    # ////////////////////////////////////////////////////////////
+
+    def parse(self, tokens, tree_class=Tree):
+        tokens = list(tokens)
+        self._grammar.check_coverage(tokens)
+
+        # Initialize ourselves.
+        self.initialize(tokens)
+
+        # Step until no more edges are generated.
+        for e in self.step():
+            if e is None:
+                break
+
+        # Return an iterator of complete parses.
+        return self.parses(tree_class=tree_class)
+
+
+########################################################################
+##  Demo Code
+########################################################################
+
+
+def demo_grammar():
+    from nltk.grammar import CFG
+
+    return CFG.fromstring(
+        """
+S  -> NP VP
+PP -> "with" NP
+NP -> NP PP
+VP -> VP PP
+VP -> Verb NP
+VP -> Verb
+NP -> Det Noun
+NP -> "John"
+NP -> "I"
+Det -> "the"
+Det -> "my"
+Det -> "a"
+Noun -> "dog"
+Noun -> "cookie"
+Verb -> "ate"
+Verb -> "saw"
+Prep -> "with"
+Prep -> "under"
+"""
+    )
+
+
+def demo(
+    choice=None,
+    print_times=True,
+    print_grammar=False,
+    print_trees=True,
+    trace=2,
+    sent="I saw John with a dog with my cookie",
+    numparses=5,
+):
+    """
+    A demonstration of the chart parsers.
+    """
+    import sys
+    import time
+
+    from nltk import CFG, Production, nonterminals
+
+    # The grammar for ChartParser and SteppingChartParser:
+    grammar = demo_grammar()
+    if print_grammar:
+        print("* Grammar")
+        print(grammar)
+
+    # Tokenize the sample sentence.
+    print("* Sentence:")
+    print(sent)
+    tokens = sent.split()
+    print(tokens)
+    print()
+
+    # Ask the user which parser to test,
+    # if the parser wasn't provided as an argument
+    if choice is None:
+        print("  1: Top-down chart parser")
+        print("  2: Bottom-up chart parser")
+        print("  3: Bottom-up left-corner chart parser")
+        print("  4: Left-corner chart parser with bottom-up filter")
+        print("  5: Stepping chart parser (alternating top-down & bottom-up)")
+        print("  6: All parsers")
+        print("\nWhich parser (1-6)? ", end=" ")
+        choice = sys.stdin.readline().strip()
+        print()
+
+    choice = str(choice)
+    if choice not in "123456":
+        print("Bad parser number")
+        return
+
+    # Keep track of how long each parser takes.
+    times = {}
+
+    strategies = {
+        "1": ("Top-down", TD_STRATEGY),
+        "2": ("Bottom-up", BU_STRATEGY),
+        "3": ("Bottom-up left-corner", BU_LC_STRATEGY),
+        "4": ("Filtered left-corner", LC_STRATEGY),
+    }
+    choices = []
+    if choice in strategies:
+        choices = [choice]
+    if choice == "6":
+        choices = "1234"
+
+    # Run the requested chart parser(s), except the stepping parser.
+    for strategy in choices:
+        print("* Strategy: " + strategies[strategy][0])
+        print()
+        cp = ChartParser(grammar, strategies[strategy][1], trace=trace)
+        t = time.time()
+        chart = cp.chart_parse(tokens)
+        parses = list(chart.parses(grammar.start()))
+
+        times[strategies[strategy][0]] = time.time() - t
+        print("Nr edges in chart:", len(chart.edges()))
+        if numparses:
+            assert len(parses) == numparses, "Not all parses found"
+        if print_trees:
+            for tree in parses:
+                print(tree)
+        else:
+            print("Nr trees:", len(parses))
+        print()
+
+    # Run the stepping parser, if requested.
+    if choice in "56":
+        print("* Strategy: Stepping (top-down vs bottom-up)")
+        print()
+        t = time.time()
+        cp = SteppingChartParser(grammar, trace=trace)
+        cp.initialize(tokens)
+        for i in range(5):
+            print("*** SWITCH TO TOP DOWN")
+            cp.set_strategy(TD_STRATEGY)
+            for j, e in enumerate(cp.step()):
+                if j > 20 or e is None:
+                    break
+            print("*** SWITCH TO BOTTOM UP")
+            cp.set_strategy(BU_STRATEGY)
+            for j, e in enumerate(cp.step()):
+                if j > 20 or e is None:
+                    break
+        times["Stepping"] = time.time() - t
+        print("Nr edges in chart:", len(cp.chart().edges()))
+        if numparses:
+            assert len(list(cp.parses())) == numparses, "Not all parses found"
+        if print_trees:
+            for tree in cp.parses():
+                print(tree)
+        else:
+            print("Nr trees:", len(list(cp.parses())))
+        print()
+
+    # Print the times of all parsers:
+    if not (print_times and times):
+        return
+    print("* Parsing times")
+    print()
+    maxlen = max(len(key) for key in times)
+    format = "%" + repr(maxlen) + "s parser: %6.3fsec"
+    times_items = times.items()
+    for parser, t in sorted(times_items, key=lambda a: a[1]):
+        print(format % (parser, t))
+
+
+if __name__ == "__main__":
+    demo()