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backend/venv/Lib/site-packages/nltk/inference/__init__.py

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+# Natural Language Toolkit: Inference
+#
+# Copyright (C) 2001-2025 NLTK Project
+# Author: Dan Garrette <dhgarrette@gmail.com>
+#         Ewan Klein <ewan@inf.ed.ac.uk>
+#
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+Classes and interfaces for theorem proving and model building.
+"""
+
+from nltk.inference.api import ParallelProverBuilder, ParallelProverBuilderCommand
+from nltk.inference.discourse import (
+    CfgReadingCommand,
+    DiscourseTester,
+    DrtGlueReadingCommand,
+    ReadingCommand,
+)
+from nltk.inference.mace import Mace, MaceCommand
+from nltk.inference.prover9 import Prover9, Prover9Command
+from nltk.inference.resolution import ResolutionProver, ResolutionProverCommand
+from nltk.inference.tableau import TableauProver, TableauProverCommand

backend/venv/Lib/site-packages/nltk/inference/api.py

@@ -0,0 +1,614 @@
+# Natural Language Toolkit: Classifier Interface
+#
+# Author: Ewan Klein <ewan@inf.ed.ac.uk>
+#         Dan Garrette <dhgarrette@gmail.com>
+#
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+Interfaces and base classes for theorem provers and model builders.
+
+``Prover`` is a standard interface for a theorem prover which tries to prove a goal from a
+list of assumptions.
+
+``ModelBuilder`` is a standard interface for a model builder. Given just a set of assumptions.
+the model builder tries to build a model for the assumptions. Given a set of assumptions and a
+goal *G*, the model builder tries to find a counter-model, in the sense of a model that will satisfy
+the assumptions plus the negation of *G*.
+"""
+
+import threading
+import time
+from abc import ABCMeta, abstractmethod
+
+
+class Prover(metaclass=ABCMeta):
+    """
+    Interface for trying to prove a goal from assumptions.  Both the goal and
+    the assumptions are constrained to be formulas of ``logic.Expression``.
+    """
+
+    def prove(self, goal=None, assumptions=None, verbose=False):
+        """
+        :return: Whether the proof was successful or not.
+        :rtype: bool
+        """
+        return self._prove(goal, assumptions, verbose)[0]
+
+    @abstractmethod
+    def _prove(self, goal=None, assumptions=None, verbose=False):
+        """
+        :return: Whether the proof was successful or not, along with the proof
+        :rtype: tuple: (bool, str)
+        """
+
+
+class ModelBuilder(metaclass=ABCMeta):
+    """
+    Interface for trying to build a model of set of formulas.
+    Open formulas are assumed to be universally quantified.
+    Both the goal and the assumptions are constrained to be formulas
+    of ``logic.Expression``.
+    """
+
+    def build_model(self, goal=None, assumptions=None, verbose=False):
+        """
+        Perform the actual model building.
+        :return: Whether a model was generated
+        :rtype: bool
+        """
+        return self._build_model(goal, assumptions, verbose)[0]
+
+    @abstractmethod
+    def _build_model(self, goal=None, assumptions=None, verbose=False):
+        """
+        Perform the actual model building.
+        :return: Whether a model was generated, and the model itself
+        :rtype: tuple(bool, sem.Valuation)
+        """
+
+
+class TheoremToolCommand(metaclass=ABCMeta):
+    """
+    This class holds a goal and a list of assumptions to be used in proving
+    or model building.
+    """
+
+    @abstractmethod
+    def add_assumptions(self, new_assumptions):
+        """
+        Add new assumptions to the assumption list.
+
+        :param new_assumptions: new assumptions
+        :type new_assumptions: list(sem.Expression)
+        """
+
+    @abstractmethod
+    def retract_assumptions(self, retracted, debug=False):
+        """
+        Retract assumptions from the assumption list.
+
+        :param debug: If True, give warning when ``retracted`` is not present on
+            assumptions list.
+        :type debug: bool
+        :param retracted: assumptions to be retracted
+        :type retracted: list(sem.Expression)
+        """
+
+    @abstractmethod
+    def assumptions(self):
+        """
+        List the current assumptions.
+
+        :return: list of ``Expression``
+        """
+
+    @abstractmethod
+    def goal(self):
+        """
+        Return the goal
+
+        :return: ``Expression``
+        """
+
+    @abstractmethod
+    def print_assumptions(self):
+        """
+        Print the list of the current assumptions.
+        """
+
+
+class ProverCommand(TheoremToolCommand):
+    """
+    This class holds a ``Prover``, a goal, and a list of assumptions.  When
+    prove() is called, the ``Prover`` is executed with the goal and assumptions.
+    """
+
+    @abstractmethod
+    def prove(self, verbose=False):
+        """
+        Perform the actual proof.
+        """
+
+    @abstractmethod
+    def proof(self, simplify=True):
+        """
+        Return the proof string
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+
+    @abstractmethod
+    def get_prover(self):
+        """
+        Return the prover object
+        :return: ``Prover``
+        """
+
+
+class ModelBuilderCommand(TheoremToolCommand):
+    """
+    This class holds a ``ModelBuilder``, a goal, and a list of assumptions.
+    When build_model() is called, the ``ModelBuilder`` is executed with the goal
+    and assumptions.
+    """
+
+    @abstractmethod
+    def build_model(self, verbose=False):
+        """
+        Perform the actual model building.
+        :return: A model if one is generated; None otherwise.
+        :rtype: sem.Valuation
+        """
+
+    @abstractmethod
+    def model(self, format=None):
+        """
+        Return a string representation of the model
+
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+
+    @abstractmethod
+    def get_model_builder(self):
+        """
+        Return the model builder object
+        :return: ``ModelBuilder``
+        """
+
+
+class BaseTheoremToolCommand(TheoremToolCommand):
+    """
+    This class holds a goal and a list of assumptions to be used in proving
+    or model building.
+    """
+
+    def __init__(self, goal=None, assumptions=None):
+        """
+        :param goal: Input expression to prove
+        :type goal: sem.Expression
+        :param assumptions: Input expressions to use as assumptions in
+            the proof.
+        :type assumptions: list(sem.Expression)
+        """
+        self._goal = goal
+
+        if not assumptions:
+            self._assumptions = []
+        else:
+            self._assumptions = list(assumptions)
+
+        self._result = None
+        """A holder for the result, to prevent unnecessary re-proving"""
+
+    def add_assumptions(self, new_assumptions):
+        """
+        Add new assumptions to the assumption list.
+
+        :param new_assumptions: new assumptions
+        :type new_assumptions: list(sem.Expression)
+        """
+        self._assumptions.extend(new_assumptions)
+        self._result = None
+
+    def retract_assumptions(self, retracted, debug=False):
+        """
+        Retract assumptions from the assumption list.
+
+        :param debug: If True, give warning when ``retracted`` is not present on
+            assumptions list.
+        :type debug: bool
+        :param retracted: assumptions to be retracted
+        :type retracted: list(sem.Expression)
+        """
+        retracted = set(retracted)
+        result_list = list(filter(lambda a: a not in retracted, self._assumptions))
+        if debug and result_list == self._assumptions:
+            print(Warning("Assumptions list has not been changed:"))
+            self.print_assumptions()
+
+        self._assumptions = result_list
+
+        self._result = None
+
+    def assumptions(self):
+        """
+        List the current assumptions.
+
+        :return: list of ``Expression``
+        """
+        return self._assumptions
+
+    def goal(self):
+        """
+        Return the goal
+
+        :return: ``Expression``
+        """
+        return self._goal
+
+    def print_assumptions(self):
+        """
+        Print the list of the current assumptions.
+        """
+        for a in self.assumptions():
+            print(a)
+
+
+class BaseProverCommand(BaseTheoremToolCommand, ProverCommand):
+    """
+    This class holds a ``Prover``, a goal, and a list of assumptions.  When
+    prove() is called, the ``Prover`` is executed with the goal and assumptions.
+    """
+
+    def __init__(self, prover, goal=None, assumptions=None):
+        """
+        :param prover: The theorem tool to execute with the assumptions
+        :type prover: Prover
+        :see: ``BaseTheoremToolCommand``
+        """
+        self._prover = prover
+        """The theorem tool to execute with the assumptions"""
+
+        BaseTheoremToolCommand.__init__(self, goal, assumptions)
+
+        self._proof = None
+
+    def prove(self, verbose=False):
+        """
+        Perform the actual proof.  Store the result to prevent unnecessary
+        re-proving.
+        """
+        if self._result is None:
+            self._result, self._proof = self._prover._prove(
+                self.goal(), self.assumptions(), verbose
+            )
+        return self._result
+
+    def proof(self, simplify=True):
+        """
+        Return the proof string
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+        if self._result is None:
+            raise LookupError("You have to call prove() first to get a proof!")
+        else:
+            return self.decorate_proof(self._proof, simplify)
+
+    def decorate_proof(self, proof_string, simplify=True):
+        """
+        Modify and return the proof string
+        :param proof_string: str the proof to decorate
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+        return proof_string
+
+    def get_prover(self):
+        return self._prover
+
+
+class BaseModelBuilderCommand(BaseTheoremToolCommand, ModelBuilderCommand):
+    """
+    This class holds a ``ModelBuilder``, a goal, and a list of assumptions.  When
+    build_model() is called, the ``ModelBuilder`` is executed with the goal and
+    assumptions.
+    """
+
+    def __init__(self, modelbuilder, goal=None, assumptions=None):
+        """
+        :param modelbuilder: The theorem tool to execute with the assumptions
+        :type modelbuilder: ModelBuilder
+        :see: ``BaseTheoremToolCommand``
+        """
+        self._modelbuilder = modelbuilder
+        """The theorem tool to execute with the assumptions"""
+
+        BaseTheoremToolCommand.__init__(self, goal, assumptions)
+
+        self._model = None
+
+    def build_model(self, verbose=False):
+        """
+        Attempt to build a model.  Store the result to prevent unnecessary
+        re-building.
+        """
+        if self._result is None:
+            self._result, self._model = self._modelbuilder._build_model(
+                self.goal(), self.assumptions(), verbose
+            )
+        return self._result
+
+    def model(self, format=None):
+        """
+        Return a string representation of the model
+
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+        if self._result is None:
+            raise LookupError("You have to call build_model() first to " "get a model!")
+        else:
+            return self._decorate_model(self._model, format)
+
+    def _decorate_model(self, valuation_str, format=None):
+        """
+        :param valuation_str: str with the model builder's output
+        :param format: str indicating the format for displaying
+        :return: str
+        """
+        return valuation_str
+
+    def get_model_builder(self):
+        return self._modelbuilder
+
+
+class TheoremToolCommandDecorator(TheoremToolCommand):
+    """
+    A base decorator for the ``ProverCommandDecorator`` and
+    ``ModelBuilderCommandDecorator`` classes from which decorators can extend.
+    """
+
+    def __init__(self, command):
+        """
+        :param command: ``TheoremToolCommand`` to decorate
+        """
+        self._command = command
+
+        # The decorator has its own versions of 'result' different from the
+        # underlying command
+        self._result = None
+
+    def assumptions(self):
+        return self._command.assumptions()
+
+    def goal(self):
+        return self._command.goal()
+
+    def add_assumptions(self, new_assumptions):
+        self._command.add_assumptions(new_assumptions)
+        self._result = None
+
+    def retract_assumptions(self, retracted, debug=False):
+        self._command.retract_assumptions(retracted, debug)
+        self._result = None
+
+    def print_assumptions(self):
+        self._command.print_assumptions()
+
+
+class ProverCommandDecorator(TheoremToolCommandDecorator, ProverCommand):
+    """
+    A base decorator for the ``ProverCommand`` class from which other
+    prover command decorators can extend.
+    """
+
+    def __init__(self, proverCommand):
+        """
+        :param proverCommand: ``ProverCommand`` to decorate
+        """
+        TheoremToolCommandDecorator.__init__(self, proverCommand)
+
+        # The decorator has its own versions of 'result' and 'proof'
+        # because they may be different from the underlying command
+        self._proof = None
+
+    def prove(self, verbose=False):
+        if self._result is None:
+            prover = self.get_prover()
+            self._result, self._proof = prover._prove(
+                self.goal(), self.assumptions(), verbose
+            )
+        return self._result
+
+    def proof(self, simplify=True):
+        """
+        Return the proof string
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+        if self._result is None:
+            raise LookupError("You have to call prove() first to get a proof!")
+        else:
+            return self.decorate_proof(self._proof, simplify)
+
+    def decorate_proof(self, proof_string, simplify=True):
+        """
+        Modify and return the proof string
+        :param proof_string: str the proof to decorate
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+        return self._command.decorate_proof(proof_string, simplify)
+
+    def get_prover(self):
+        return self._command.get_prover()
+
+
+class ModelBuilderCommandDecorator(TheoremToolCommandDecorator, ModelBuilderCommand):
+    """
+    A base decorator for the ``ModelBuilderCommand`` class from which other
+    prover command decorators can extend.
+    """
+
+    def __init__(self, modelBuilderCommand):
+        """
+        :param modelBuilderCommand: ``ModelBuilderCommand`` to decorate
+        """
+        TheoremToolCommandDecorator.__init__(self, modelBuilderCommand)
+
+        # The decorator has its own versions of 'result' and 'valuation'
+        # because they may be different from the underlying command
+        self._model = None
+
+    def build_model(self, verbose=False):
+        """
+        Attempt to build a model.  Store the result to prevent unnecessary
+        re-building.
+        """
+        if self._result is None:
+            modelbuilder = self.get_model_builder()
+            self._result, self._model = modelbuilder._build_model(
+                self.goal(), self.assumptions(), verbose
+            )
+        return self._result
+
+    def model(self, format=None):
+        """
+        Return a string representation of the model
+
+        :param simplify: bool simplify the proof?
+        :return: str
+        """
+        if self._result is None:
+            raise LookupError("You have to call build_model() first to " "get a model!")
+        else:
+            return self._decorate_model(self._model, format)
+
+    def _decorate_model(self, valuation_str, format=None):
+        """
+        Modify and return the proof string
+        :param valuation_str: str with the model builder's output
+        :param format: str indicating the format for displaying
+        :return: str
+        """
+        return self._command._decorate_model(valuation_str, format)
+
+    def get_model_builder(self):
+        return self._command.get_prover()
+
+
+class ParallelProverBuilder(Prover, ModelBuilder):
+    """
+    This class stores both a prover and a model builder and when either
+    prove() or build_model() is called, then both theorem tools are run in
+    parallel.  Whichever finishes first, the prover or the model builder, is the
+    result that will be used.
+    """
+
+    def __init__(self, prover, modelbuilder):
+        self._prover = prover
+        self._modelbuilder = modelbuilder
+
+    def _prove(self, goal=None, assumptions=None, verbose=False):
+        return self._run(goal, assumptions, verbose), ""
+
+    def _build_model(self, goal=None, assumptions=None, verbose=False):
+        return not self._run(goal, assumptions, verbose), ""
+
+    def _run(self, goal, assumptions, verbose):
+        # Set up two thread, Prover and ModelBuilder to run in parallel
+        tp_thread = TheoremToolThread(
+            lambda: self._prover.prove(goal, assumptions, verbose), verbose, "TP"
+        )
+        mb_thread = TheoremToolThread(
+            lambda: self._modelbuilder.build_model(goal, assumptions, verbose),
+            verbose,
+            "MB",
+        )
+
+        tp_thread.start()
+        mb_thread.start()
+
+        while tp_thread.is_alive() and mb_thread.is_alive():
+            # wait until either the prover or the model builder is done
+            pass
+
+        if tp_thread.result is not None:
+            return tp_thread.result
+        elif mb_thread.result is not None:
+            return not mb_thread.result
+        else:
+            return None
+
+
+class ParallelProverBuilderCommand(BaseProverCommand, BaseModelBuilderCommand):
+    """
+    This command stores both a prover and a model builder and when either
+    prove() or build_model() is called, then both theorem tools are run in
+    parallel.  Whichever finishes first, the prover or the model builder, is the
+    result that will be used.
+
+    Because the theorem prover result is the opposite of the model builder
+    result, we will treat self._result as meaning "proof found/no model found".
+    """
+
+    def __init__(self, prover, modelbuilder, goal=None, assumptions=None):
+        BaseProverCommand.__init__(self, prover, goal, assumptions)
+        BaseModelBuilderCommand.__init__(self, modelbuilder, goal, assumptions)
+
+    def prove(self, verbose=False):
+        return self._run(verbose)
+
+    def build_model(self, verbose=False):
+        return not self._run(verbose)
+
+    def _run(self, verbose):
+        # Set up two thread, Prover and ModelBuilder to run in parallel
+        tp_thread = TheoremToolThread(
+            lambda: BaseProverCommand.prove(self, verbose), verbose, "TP"
+        )
+        mb_thread = TheoremToolThread(
+            lambda: BaseModelBuilderCommand.build_model(self, verbose), verbose, "MB"
+        )
+
+        tp_thread.start()
+        mb_thread.start()
+
+        while tp_thread.is_alive() and mb_thread.is_alive():
+            # wait until either the prover or the model builder is done
+            pass
+
+        if tp_thread.result is not None:
+            self._result = tp_thread.result
+        elif mb_thread.result is not None:
+            self._result = not mb_thread.result
+        return self._result
+
+
+class TheoremToolThread(threading.Thread):
+    def __init__(self, command, verbose, name=None):
+        threading.Thread.__init__(self)
+        self._command = command
+        self._result = None
+        self._verbose = verbose
+        self._name = name
+
+    def run(self):
+        try:
+            self._result = self._command()
+            if self._verbose:
+                print(
+                    "Thread %s finished with result %s at %s"
+                    % (self._name, self._result, time.localtime(time.time()))
+                )
+        except Exception as e:
+            print(e)
+            print("Thread %s completed abnormally" % (self._name))
+
+    @property
+    def result(self):
+        return self._result

backend/venv/Lib/site-packages/nltk/inference/discourse.py

@@ -0,0 +1,651 @@
+# Natural Language Toolkit: Discourse Processing
+#
+# Author: Ewan Klein <ewan@inf.ed.ac.uk>
+#         Dan Garrette <dhgarrette@gmail.com>
+#
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+r"""
+Module for incrementally developing simple discourses, and checking for semantic ambiguity,
+consistency and informativeness.
+
+Many of the ideas are based on the CURT family of programs of Blackburn and Bos
+(see http://homepages.inf.ed.ac.uk/jbos/comsem/book1.html).
+
+Consistency checking is carried out  by using the ``mace`` module to call the Mace4 model builder.
+Informativeness checking is carried out with a call to ``Prover.prove()`` from
+the ``inference``  module.
+
+``DiscourseTester`` is a constructor for discourses.
+The basic data structure is a list of sentences, stored as ``self._sentences``. Each sentence in the list
+is assigned a "sentence ID" (``sid``) of the form ``s``\ *i*. For example::
+
+    s0: A boxer walks
+    s1: Every boxer chases a girl
+
+Each sentence can be ambiguous between a number of readings, each of which receives a
+"reading ID" (``rid``) of the form ``s``\ *i* -``r``\ *j*. For example::
+
+    s0 readings:
+
+    s0-r1: some x.(boxer(x) & walk(x))
+    s0-r0: some x.(boxerdog(x) & walk(x))
+
+A "thread" is a list of readings, represented as a list of ``rid``\ s.
+Each thread receives a "thread ID" (``tid``) of the form ``d``\ *i*.
+For example::
+
+    d0: ['s0-r0', 's1-r0']
+
+The set of all threads for a discourse is the Cartesian product of all the readings of the sequences of sentences.
+(This is not intended to scale beyond very short discourses!) The method ``readings(filter=True)`` will only show
+those threads which are consistent (taking into account any background assumptions).
+"""
+
+import os
+from abc import ABCMeta, abstractmethod
+from functools import reduce
+from operator import add, and_
+
+from nltk.data import show_cfg
+from nltk.inference.mace import MaceCommand
+from nltk.inference.prover9 import Prover9Command
+from nltk.parse import load_parser
+from nltk.parse.malt import MaltParser
+from nltk.sem.drt import AnaphoraResolutionException, resolve_anaphora
+from nltk.sem.glue import DrtGlue
+from nltk.sem.logic import Expression
+from nltk.tag import RegexpTagger
+
+
+class ReadingCommand(metaclass=ABCMeta):
+    @abstractmethod
+    def parse_to_readings(self, sentence):
+        """
+        :param sentence: the sentence to read
+        :type sentence: str
+        """
+
+    def process_thread(self, sentence_readings):
+        """
+        This method should be used to handle dependencies between readings such
+        as resolving anaphora.
+
+        :param sentence_readings: readings to process
+        :type sentence_readings: list(Expression)
+        :return: the list of readings after processing
+        :rtype: list(Expression)
+        """
+        return sentence_readings
+
+    @abstractmethod
+    def combine_readings(self, readings):
+        """
+        :param readings: readings to combine
+        :type readings: list(Expression)
+        :return: one combined reading
+        :rtype: Expression
+        """
+
+    @abstractmethod
+    def to_fol(self, expression):
+        """
+        Convert this expression into a First-Order Logic expression.
+
+        :param expression: an expression
+        :type expression: Expression
+        :return: a FOL version of the input expression
+        :rtype: Expression
+        """
+
+
+class CfgReadingCommand(ReadingCommand):
+    def __init__(self, gramfile=None):
+        """
+        :param gramfile: name of file where grammar can be loaded
+        :type gramfile: str
+        """
+        self._gramfile = (
+            gramfile if gramfile else "grammars/book_grammars/discourse.fcfg"
+        )
+        self._parser = load_parser(self._gramfile)
+
+    def parse_to_readings(self, sentence):
+        """:see: ReadingCommand.parse_to_readings()"""
+        from nltk.sem import root_semrep
+
+        tokens = sentence.split()
+        trees = self._parser.parse(tokens)
+        return [root_semrep(tree) for tree in trees]
+
+    def combine_readings(self, readings):
+        """:see: ReadingCommand.combine_readings()"""
+        return reduce(and_, readings)
+
+    def to_fol(self, expression):
+        """:see: ReadingCommand.to_fol()"""
+        return expression
+
+
+class DrtGlueReadingCommand(ReadingCommand):
+    def __init__(self, semtype_file=None, remove_duplicates=False, depparser=None):
+        """
+        :param semtype_file: name of file where grammar can be loaded
+        :param remove_duplicates: should duplicates be removed?
+        :param depparser: the dependency parser
+        """
+        if semtype_file is None:
+            semtype_file = os.path.join(
+                "grammars", "sample_grammars", "drt_glue.semtype"
+            )
+        self._glue = DrtGlue(
+            semtype_file=semtype_file,
+            remove_duplicates=remove_duplicates,
+            depparser=depparser,
+        )
+
+    def parse_to_readings(self, sentence):
+        """:see: ReadingCommand.parse_to_readings()"""
+        return self._glue.parse_to_meaning(sentence)
+
+    def process_thread(self, sentence_readings):
+        """:see: ReadingCommand.process_thread()"""
+        try:
+            return [self.combine_readings(sentence_readings)]
+        except AnaphoraResolutionException:
+            return []
+
+    def combine_readings(self, readings):
+        """:see: ReadingCommand.combine_readings()"""
+        thread_reading = reduce(add, readings)
+        return resolve_anaphora(thread_reading.simplify())
+
+    def to_fol(self, expression):
+        """:see: ReadingCommand.to_fol()"""
+        return expression.fol()
+
+
+class DiscourseTester:
+    """
+    Check properties of an ongoing discourse.
+    """
+
+    def __init__(self, input, reading_command=None, background=None):
+        """
+        Initialize a ``DiscourseTester``.
+
+        :param input: the discourse sentences
+        :type input: list of str
+        :param background: Formulas which express background assumptions
+        :type background: list(Expression)
+        """
+        self._input = input
+        self._sentences = {"s%s" % i: sent for i, sent in enumerate(input)}
+        self._models = None
+        self._readings = {}
+        self._reading_command = (
+            reading_command if reading_command else CfgReadingCommand()
+        )
+        self._threads = {}
+        self._filtered_threads = {}
+        if background is not None:
+            from nltk.sem.logic import Expression
+
+            for e in background:
+                assert isinstance(e, Expression)
+            self._background = background
+        else:
+            self._background = []
+
+    ###############################
+    # Sentences
+    ###############################
+
+    def sentences(self):
+        """
+        Display the list of sentences in the current discourse.
+        """
+        for id in sorted(self._sentences):
+            print(f"{id}: {self._sentences[id]}")
+
+    def add_sentence(self, sentence, informchk=False, consistchk=False):
+        """
+        Add a sentence to the current discourse.
+
+        Updates ``self._input`` and ``self._sentences``.
+        :param sentence: An input sentence
+        :type sentence: str
+        :param informchk: if ``True``, check that the result of adding the sentence is thread-informative. Updates ``self._readings``.
+        :param consistchk: if ``True``, check that the result of adding the sentence is thread-consistent. Updates ``self._readings``.
+
+        """
+        # check whether the new sentence is informative (i.e. not entailed by the previous discourse)
+        if informchk:
+            self.readings(verbose=False)
+            for tid in sorted(self._threads):
+                assumptions = [reading for (rid, reading) in self.expand_threads(tid)]
+                assumptions += self._background
+                for sent_reading in self._get_readings(sentence):
+                    tp = Prover9Command(goal=sent_reading, assumptions=assumptions)
+                    if tp.prove():
+                        print(
+                            "Sentence '%s' under reading '%s':"
+                            % (sentence, str(sent_reading))
+                        )
+                        print("Not informative relative to thread '%s'" % tid)
+
+        self._input.append(sentence)
+        self._sentences = {"s%s" % i: sent for i, sent in enumerate(self._input)}
+        # check whether adding the new sentence to the discourse preserves consistency (i.e. a model can be found for the combined set of
+        # of assumptions
+        if consistchk:
+            self.readings(verbose=False)
+            self.models(show=False)
+
+    def retract_sentence(self, sentence, verbose=True):
+        """
+        Remove a sentence from the current discourse.
+
+        Updates ``self._input``, ``self._sentences`` and ``self._readings``.
+        :param sentence: An input sentence
+        :type sentence: str
+        :param verbose: If ``True``,  report on the updated list of sentences.
+        """
+        try:
+            self._input.remove(sentence)
+        except ValueError:
+            print(
+                "Retraction failed. The sentence '%s' is not part of the current discourse:"
+                % sentence
+            )
+            self.sentences()
+            return None
+        self._sentences = {"s%s" % i: sent for i, sent in enumerate(self._input)}
+        self.readings(verbose=False)
+        if verbose:
+            print("Current sentences are ")
+            self.sentences()
+
+    def grammar(self):
+        """
+        Print out the grammar in use for parsing input sentences
+        """
+        show_cfg(self._reading_command._gramfile)
+
+    ###############################
+    # Readings and Threads
+    ###############################
+
+    def _get_readings(self, sentence):
+        """
+        Build a list of semantic readings for a sentence.
+
+        :rtype: list(Expression)
+        """
+        return self._reading_command.parse_to_readings(sentence)
+
+    def _construct_readings(self):
+        """
+        Use ``self._sentences`` to construct a value for ``self._readings``.
+        """
+        # re-initialize self._readings in case we have retracted a sentence
+        self._readings = {}
+        for sid in sorted(self._sentences):
+            sentence = self._sentences[sid]
+            readings = self._get_readings(sentence)
+            self._readings[sid] = {
+                f"{sid}-r{rid}": reading.simplify()
+                for rid, reading in enumerate(sorted(readings, key=str))
+            }
+
+    def _construct_threads(self):
+        """
+        Use ``self._readings`` to construct a value for ``self._threads``
+        and use the model builder to construct a value for ``self._filtered_threads``
+        """
+        thread_list = [[]]
+        for sid in sorted(self._readings):
+            thread_list = self.multiply(thread_list, sorted(self._readings[sid]))
+        self._threads = {"d%s" % tid: thread for tid, thread in enumerate(thread_list)}
+        # re-initialize the filtered threads
+        self._filtered_threads = {}
+        # keep the same ids, but only include threads which get models
+        consistency_checked = self._check_consistency(self._threads)
+        for tid, thread in self._threads.items():
+            if (tid, True) in consistency_checked:
+                self._filtered_threads[tid] = thread
+
+    def _show_readings(self, sentence=None):
+        """
+        Print out the readings for  the discourse (or a single sentence).
+        """
+        if sentence is not None:
+            print("The sentence '%s' has these readings:" % sentence)
+            for r in [str(reading) for reading in (self._get_readings(sentence))]:
+                print("    %s" % r)
+        else:
+            for sid in sorted(self._readings):
+                print()
+                print("%s readings:" % sid)
+                print()  #'-' * 30
+                for rid in sorted(self._readings[sid]):
+                    lf = self._readings[sid][rid]
+                    print(f"{rid}: {lf.normalize()}")
+
+    def _show_threads(self, filter=False, show_thread_readings=False):
+        """
+        Print out the value of ``self._threads`` or ``self._filtered_hreads``
+        """
+        threads = self._filtered_threads if filter else self._threads
+        for tid in sorted(threads):
+            if show_thread_readings:
+                readings = [
+                    self._readings[rid.split("-")[0]][rid] for rid in self._threads[tid]
+                ]
+                try:
+                    thread_reading = (
+                        ": %s"
+                        % self._reading_command.combine_readings(readings).normalize()
+                    )
+                except Exception as e:
+                    thread_reading = ": INVALID: %s" % e.__class__.__name__
+            else:
+                thread_reading = ""
+
+            print("%s:" % tid, self._threads[tid], thread_reading)
+
+    def readings(
+        self,
+        sentence=None,
+        threaded=False,
+        verbose=True,
+        filter=False,
+        show_thread_readings=False,
+    ):
+        """
+        Construct and show the readings of the discourse (or of a single sentence).
+
+        :param sentence: test just this sentence
+        :type sentence: str
+        :param threaded: if ``True``, print out each thread ID and the corresponding thread.
+        :param filter: if ``True``, only print out consistent thread IDs and threads.
+        """
+        self._construct_readings()
+        self._construct_threads()
+
+        # if we are filtering or showing thread readings, show threads
+        if filter or show_thread_readings:
+            threaded = True
+
+        if verbose:
+            if not threaded:
+                self._show_readings(sentence=sentence)
+            else:
+                self._show_threads(
+                    filter=filter, show_thread_readings=show_thread_readings
+                )
+
+    def expand_threads(self, thread_id, threads=None):
+        """
+        Given a thread ID, find the list of ``logic.Expression`` objects corresponding to the reading IDs in that thread.
+
+        :param thread_id: thread ID
+        :type thread_id: str
+        :param threads: a mapping from thread IDs to lists of reading IDs
+        :type threads: dict
+        :return: A list of pairs ``(rid, reading)`` where reading is the ``logic.Expression`` associated with a reading ID
+        :rtype: list of tuple
+        """
+        if threads is None:
+            threads = self._threads
+        return [
+            (rid, self._readings[sid][rid])
+            for rid in threads[thread_id]
+            for sid in rid.split("-")[:1]
+        ]
+
+    ###############################
+    # Models and Background
+    ###############################
+
+    def _check_consistency(self, threads, show=False, verbose=False):
+        results = []
+        for tid in sorted(threads):
+            assumptions = [
+                reading for (rid, reading) in self.expand_threads(tid, threads=threads)
+            ]
+            assumptions = list(
+                map(
+                    self._reading_command.to_fol,
+                    self._reading_command.process_thread(assumptions),
+                )
+            )
+            if assumptions:
+                assumptions += self._background
+                # if Mace4 finds a model, it always seems to find it quickly
+                mb = MaceCommand(None, assumptions, max_models=20)
+                modelfound = mb.build_model()
+            else:
+                modelfound = False
+            results.append((tid, modelfound))
+            if show:
+                spacer(80)
+                print("Model for Discourse Thread %s" % tid)
+                spacer(80)
+                if verbose:
+                    for a in assumptions:
+                        print(a)
+                    spacer(80)
+                if modelfound:
+                    print(mb.model(format="cooked"))
+                else:
+                    print("No model found!\n")
+        return results
+
+    def models(self, thread_id=None, show=True, verbose=False):
+        """
+        Call Mace4 to build a model for each current discourse thread.
+
+        :param thread_id: thread ID
+        :type thread_id: str
+        :param show: If ``True``, display the model that has been found.
+        """
+        self._construct_readings()
+        self._construct_threads()
+        threads = {thread_id: self._threads[thread_id]} if thread_id else self._threads
+
+        for tid, modelfound in self._check_consistency(
+            threads, show=show, verbose=verbose
+        ):
+            idlist = [rid for rid in threads[tid]]
+
+            if not modelfound:
+                print(f"Inconsistent discourse: {tid} {idlist}:")
+                for rid, reading in self.expand_threads(tid):
+                    print(f"    {rid}: {reading.normalize()}")
+                print()
+            else:
+                print(f"Consistent discourse: {tid} {idlist}:")
+                for rid, reading in self.expand_threads(tid):
+                    print(f"    {rid}: {reading.normalize()}")
+                print()
+
+    def add_background(self, background, verbose=False):
+        """
+        Add a list of background assumptions for reasoning about the discourse.
+
+        When called,  this method also updates the discourse model's set of readings and threads.
+        :param background: Formulas which contain background information
+        :type background: list(Expression)
+        """
+        from nltk.sem.logic import Expression
+
+        for count, e in enumerate(background):
+            assert isinstance(e, Expression)
+            if verbose:
+                print("Adding assumption %s to background" % count)
+            self._background.append(e)
+
+        # update the state
+        self._construct_readings()
+        self._construct_threads()
+
+    def background(self):
+        """
+        Show the current background assumptions.
+        """
+        for e in self._background:
+            print(str(e))
+
+    ###############################
+    # Misc
+    ###############################
+
+    @staticmethod
+    def multiply(discourse, readings):
+        """
+        Multiply every thread in ``discourse`` by every reading in ``readings``.
+
+        Given discourse = [['A'], ['B']], readings = ['a', 'b', 'c'] , returns
+        [['A', 'a'], ['A', 'b'], ['A', 'c'], ['B', 'a'], ['B', 'b'], ['B', 'c']]
+
+        :param discourse: the current list of readings
+        :type discourse: list of lists
+        :param readings: an additional list of readings
+        :type readings: list(Expression)
+        :rtype: A list of lists
+        """
+        result = []
+        for sublist in discourse:
+            for r in readings:
+                new = []
+                new += sublist
+                new.append(r)
+                result.append(new)
+        return result
+
+
+def load_fol(s):
+    """
+    Temporarily duplicated from ``nltk.sem.util``.
+    Convert a  file of first order formulas into a list of ``Expression`` objects.
+
+    :param s: the contents of the file
+    :type s: str
+    :return: a list of parsed formulas.
+    :rtype: list(Expression)
+    """
+    statements = []
+    for linenum, line in enumerate(s.splitlines()):
+        line = line.strip()
+        if line.startswith("#") or line == "":
+            continue
+        try:
+            statements.append(Expression.fromstring(line))
+        except Exception as e:
+            raise ValueError(f"Unable to parse line {linenum}: {line}") from e
+    return statements
+
+
+###############################
+# Demo
+###############################
+def discourse_demo(reading_command=None):
+    """
+    Illustrate the various methods of ``DiscourseTester``
+    """
+    dt = DiscourseTester(
+        ["A boxer walks", "Every boxer chases a girl"], reading_command
+    )
+    dt.models()
+    print()
+    # dt.grammar()
+    print()
+    dt.sentences()
+    print()
+    dt.readings()
+    print()
+    dt.readings(threaded=True)
+    print()
+    dt.models("d1")
+    dt.add_sentence("John is a boxer")
+    print()
+    dt.sentences()
+    print()
+    dt.readings(threaded=True)
+    print()
+    dt = DiscourseTester(
+        ["A student dances", "Every student is a person"], reading_command
+    )
+    print()
+    dt.add_sentence("No person dances", consistchk=True)
+    print()
+    dt.readings()
+    print()
+    dt.retract_sentence("No person dances", verbose=True)
+    print()
+    dt.models()
+    print()
+    dt.readings("A person dances")
+    print()
+    dt.add_sentence("A person dances", informchk=True)
+    dt = DiscourseTester(
+        ["Vincent is a boxer", "Fido is a boxer", "Vincent is married", "Fido barks"],
+        reading_command,
+    )
+    dt.readings(filter=True)
+    import nltk.data
+
+    background_file = os.path.join("grammars", "book_grammars", "background.fol")
+    background = nltk.data.load(background_file)
+
+    print()
+    dt.add_background(background, verbose=False)
+    dt.background()
+    print()
+    dt.readings(filter=True)
+    print()
+    dt.models()
+
+
+def drt_discourse_demo(reading_command=None):
+    """
+    Illustrate the various methods of ``DiscourseTester``
+    """
+    dt = DiscourseTester(["every dog chases a boy", "he runs"], reading_command)
+    dt.models()
+    print()
+    dt.sentences()
+    print()
+    dt.readings()
+    print()
+    dt.readings(show_thread_readings=True)
+    print()
+    dt.readings(filter=True, show_thread_readings=True)
+
+
+def spacer(num=30):
+    print("-" * num)
+
+
+def demo():
+    discourse_demo()
+
+    tagger = RegexpTagger(
+        [
+            ("^(chases|runs)$", "VB"),
+            ("^(a)$", "ex_quant"),
+            ("^(every)$", "univ_quant"),
+            ("^(dog|boy)$", "NN"),
+            ("^(he)$", "PRP"),
+        ]
+    )
+    depparser = MaltParser(tagger=tagger)
+    drt_discourse_demo(
+        DrtGlueReadingCommand(remove_duplicates=False, depparser=depparser)
+    )
+
+
+if __name__ == "__main__":
+    demo()

backend/venv/Lib/site-packages/nltk/inference/mace.py

@@ -0,0 +1,383 @@
+# Natural Language Toolkit: Interface to the Mace4 Model Builder
+#
+# Author: Dan Garrette <dhgarrette@gmail.com>
+#         Ewan Klein <ewan@inf.ed.ac.uk>
+
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+A model builder that makes use of the external 'Mace4' package.
+"""
+
+import os
+import tempfile
+
+from nltk.inference.api import BaseModelBuilderCommand, ModelBuilder
+from nltk.inference.prover9 import Prover9CommandParent, Prover9Parent
+from nltk.sem import Expression, Valuation
+from nltk.sem.logic import is_indvar
+
+
+class MaceCommand(Prover9CommandParent, BaseModelBuilderCommand):
+    """
+    A ``MaceCommand`` specific to the ``Mace`` model builder.  It contains
+    a print_assumptions() method that is used to print the list
+    of assumptions in multiple formats.
+    """
+
+    _interpformat_bin = None
+
+    def __init__(self, goal=None, assumptions=None, max_models=500, model_builder=None):
+        """
+        :param goal: Input expression to prove
+        :type goal: sem.Expression
+        :param assumptions: Input expressions to use as assumptions in
+            the proof.
+        :type assumptions: list(sem.Expression)
+        :param max_models: The maximum number of models that Mace will try before
+            simply returning false. (Use 0 for no maximum.)
+        :type max_models: int
+        """
+        if model_builder is not None:
+            assert isinstance(model_builder, Mace)
+        else:
+            model_builder = Mace(max_models)
+
+        BaseModelBuilderCommand.__init__(self, model_builder, goal, assumptions)
+
+    @property
+    def valuation(mbc):
+        return mbc.model("valuation")
+
+    def _convert2val(self, valuation_str):
+        """
+        Transform the output file into an NLTK-style Valuation.
+
+        :return: A model if one is generated; None otherwise.
+        :rtype: sem.Valuation
+        """
+        valuation_standard_format = self._transform_output(valuation_str, "standard")
+
+        val = []
+        for line in valuation_standard_format.splitlines(False):
+            l = line.strip()
+
+            if l.startswith("interpretation"):
+                # find the number of entities in the model
+                num_entities = int(l[l.index("(") + 1 : l.index(",")].strip())
+
+            elif l.startswith("function") and l.find("_") == -1:
+                # replace the integer identifier with a corresponding alphabetic character
+                name = l[l.index("(") + 1 : l.index(",")].strip()
+                if is_indvar(name):
+                    name = name.upper()
+                value = int(l[l.index("[") + 1 : l.index("]")].strip())
+                val.append((name, MaceCommand._make_model_var(value)))
+
+            elif l.startswith("relation"):
+                l = l[l.index("(") + 1 :]
+                if "(" in l:
+                    # relation is not nullary
+                    name = l[: l.index("(")].strip()
+                    values = [
+                        int(v.strip())
+                        for v in l[l.index("[") + 1 : l.index("]")].split(",")
+                    ]
+                    val.append(
+                        (name, MaceCommand._make_relation_set(num_entities, values))
+                    )
+                else:
+                    # relation is nullary
+                    name = l[: l.index(",")].strip()
+                    value = int(l[l.index("[") + 1 : l.index("]")].strip())
+                    val.append((name, value == 1))
+
+        return Valuation(val)
+
+    @staticmethod
+    def _make_relation_set(num_entities, values):
+        """
+        Convert a Mace4-style relation table into a dictionary.
+
+        :param num_entities: the number of entities in the model; determines the row length in the table.
+        :type num_entities: int
+        :param values: a list of 1's and 0's that represent whether a relation holds in a Mace4 model.
+        :type values: list of int
+        """
+        r = set()
+        for position in [pos for (pos, v) in enumerate(values) if v == 1]:
+            r.add(
+                tuple(MaceCommand._make_relation_tuple(position, values, num_entities))
+            )
+        return r
+
+    @staticmethod
+    def _make_relation_tuple(position, values, num_entities):
+        if len(values) == 1:
+            return []
+        else:
+            sublist_size = len(values) // num_entities
+            sublist_start = position // sublist_size
+            sublist_position = int(position % sublist_size)
+
+            sublist = values[
+                sublist_start * sublist_size : (sublist_start + 1) * sublist_size
+            ]
+            return [
+                MaceCommand._make_model_var(sublist_start)
+            ] + MaceCommand._make_relation_tuple(
+                sublist_position, sublist, num_entities
+            )
+
+    @staticmethod
+    def _make_model_var(value):
+        """
+        Pick an alphabetic character as identifier for an entity in the model.
+
+        :param value: where to index into the list of characters
+        :type value: int
+        """
+        letter = [
+            "a",
+            "b",
+            "c",
+            "d",
+            "e",
+            "f",
+            "g",
+            "h",
+            "i",
+            "j",
+            "k",
+            "l",
+            "m",
+            "n",
+            "o",
+            "p",
+            "q",
+            "r",
+            "s",
+            "t",
+            "u",
+            "v",
+            "w",
+            "x",
+            "y",
+            "z",
+        ][value]
+        num = value // 26
+        return letter + str(num) if num > 0 else letter
+
+    def _decorate_model(self, valuation_str, format):
+        """
+        Print out a Mace4 model using any Mace4 ``interpformat`` format.
+        See https://www.cs.unm.edu/~mccune/mace4/manual/ for details.
+
+        :param valuation_str: str with the model builder's output
+        :param format: str indicating the format for displaying
+        models. Defaults to 'standard' format.
+        :return: str
+        """
+        if not format:
+            return valuation_str
+        elif format == "valuation":
+            return self._convert2val(valuation_str)
+        else:
+            return self._transform_output(valuation_str, format)
+
+    def _transform_output(self, valuation_str, format):
+        """
+        Transform the output file into any Mace4 ``interpformat`` format.
+
+        :param format: Output format for displaying models.
+        :type format: str
+        """
+        if format in [
+            "standard",
+            "standard2",
+            "portable",
+            "tabular",
+            "raw",
+            "cooked",
+            "xml",
+            "tex",
+        ]:
+            return self._call_interpformat(valuation_str, [format])[0]
+        else:
+            raise LookupError("The specified format does not exist")
+
+    def _call_interpformat(self, input_str, args=[], verbose=False):
+        """
+        Call the ``interpformat`` binary with the given input.
+
+        :param input_str: A string whose contents are used as stdin.
+        :param args: A list of command-line arguments.
+        :return: A tuple (stdout, returncode)
+        :see: ``config_prover9``
+        """
+        if self._interpformat_bin is None:
+            self._interpformat_bin = self._modelbuilder._find_binary(
+                "interpformat", verbose
+            )
+
+        return self._modelbuilder._call(
+            input_str, self._interpformat_bin, args, verbose
+        )
+
+
+class Mace(Prover9Parent, ModelBuilder):
+    _mace4_bin = None
+
+    def __init__(self, end_size=500):
+        self._end_size = end_size
+        """The maximum model size that Mace will try before
+           simply returning false. (Use -1 for no maximum.)"""
+
+    def _build_model(self, goal=None, assumptions=None, verbose=False):
+        """
+        Use Mace4 to build a first order model.
+
+        :return: ``True`` if a model was found (i.e. Mace returns value of 0),
+        else ``False``
+        """
+        if not assumptions:
+            assumptions = []
+
+        stdout, returncode = self._call_mace4(
+            self.prover9_input(goal, assumptions), verbose=verbose
+        )
+        return (returncode == 0, stdout)
+
+    def _call_mace4(self, input_str, args=[], verbose=False):
+        """
+        Call the ``mace4`` binary with the given input.
+
+        :param input_str: A string whose contents are used as stdin.
+        :param args: A list of command-line arguments.
+        :return: A tuple (stdout, returncode)
+        :see: ``config_prover9``
+        """
+        if self._mace4_bin is None:
+            self._mace4_bin = self._find_binary("mace4", verbose)
+
+        updated_input_str = ""
+        if self._end_size > 0:
+            updated_input_str += "assign(end_size, %d).\n\n" % self._end_size
+        updated_input_str += input_str
+
+        return self._call(updated_input_str, self._mace4_bin, args, verbose)
+
+
+def spacer(num=30):
+    print("-" * num)
+
+
+def decode_result(found):
+    """
+    Decode the result of model_found()
+
+    :param found: The output of model_found()
+    :type found: bool
+    """
+    return {True: "Countermodel found", False: "No countermodel found", None: "None"}[
+        found
+    ]
+
+
+def test_model_found(arguments):
+    """
+    Try some proofs and exhibit the results.
+    """
+    for goal, assumptions in arguments:
+        g = Expression.fromstring(goal)
+        alist = [lp.parse(a) for a in assumptions]
+        m = MaceCommand(g, assumptions=alist, max_models=50)
+        found = m.build_model()
+        for a in alist:
+            print("   %s" % a)
+        print(f"|- {g}: {decode_result(found)}\n")
+
+
+def test_build_model(arguments):
+    """
+    Try to build a ``nltk.sem.Valuation``.
+    """
+    g = Expression.fromstring("all x.man(x)")
+    alist = [
+        Expression.fromstring(a)
+        for a in [
+            "man(John)",
+            "man(Socrates)",
+            "man(Bill)",
+            "some x.(-(x = John) & man(x) & sees(John,x))",
+            "some x.(-(x = Bill) & man(x))",
+            "all x.some y.(man(x) -> gives(Socrates,x,y))",
+        ]
+    ]
+
+    m = MaceCommand(g, assumptions=alist)
+    m.build_model()
+    spacer()
+    print("Assumptions and Goal")
+    spacer()
+    for a in alist:
+        print("   %s" % a)
+    print(f"|- {g}: {decode_result(m.build_model())}\n")
+    spacer()
+    # print(m.model('standard'))
+    # print(m.model('cooked'))
+    print("Valuation")
+    spacer()
+    print(m.valuation, "\n")
+
+
+def test_transform_output(argument_pair):
+    """
+    Transform the model into various Mace4 ``interpformat`` formats.
+    """
+    g = Expression.fromstring(argument_pair[0])
+    alist = [lp.parse(a) for a in argument_pair[1]]
+    m = MaceCommand(g, assumptions=alist)
+    m.build_model()
+    for a in alist:
+        print("   %s" % a)
+    print(f"|- {g}: {m.build_model()}\n")
+    for format in ["standard", "portable", "xml", "cooked"]:
+        spacer()
+        print("Using '%s' format" % format)
+        spacer()
+        print(m.model(format=format))
+
+
+def test_make_relation_set():
+    print(
+        MaceCommand._make_relation_set(num_entities=3, values=[1, 0, 1])
+        == {("c",), ("a",)}
+    )
+    print(
+        MaceCommand._make_relation_set(
+            num_entities=3, values=[0, 0, 0, 0, 0, 0, 1, 0, 0]
+        )
+        == {("c", "a")}
+    )
+    print(
+        MaceCommand._make_relation_set(num_entities=2, values=[0, 0, 1, 0, 0, 0, 1, 0])
+        == {("a", "b", "a"), ("b", "b", "a")}
+    )
+
+
+arguments = [
+    ("mortal(Socrates)", ["all x.(man(x) -> mortal(x))", "man(Socrates)"]),
+    ("(not mortal(Socrates))", ["all x.(man(x) -> mortal(x))", "man(Socrates)"]),
+]
+
+
+def demo():
+    test_model_found(arguments)
+    test_build_model(arguments)
+    test_transform_output(arguments[1])
+
+
+if __name__ == "__main__":
+    demo()

backend/venv/Lib/site-packages/nltk/inference/nonmonotonic.py

@@ -0,0 +1,561 @@
+# Natural Language Toolkit: Nonmonotonic Reasoning
+#
+# Author: Daniel H. Garrette <dhgarrette@gmail.com>
+#
+# Copyright (C) 2001-2025 NLTK Project
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+A module to perform nonmonotonic reasoning.  The ideas and demonstrations in
+this module are based on "Logical Foundations of Artificial Intelligence" by
+Michael R. Genesereth and Nils J. Nilsson.
+"""
+
+from collections import defaultdict
+from functools import reduce
+
+from nltk.inference.api import Prover, ProverCommandDecorator
+from nltk.inference.prover9 import Prover9, Prover9Command
+from nltk.sem.logic import (
+    AbstractVariableExpression,
+    AllExpression,
+    AndExpression,
+    ApplicationExpression,
+    BooleanExpression,
+    EqualityExpression,
+    ExistsExpression,
+    Expression,
+    ImpExpression,
+    NegatedExpression,
+    Variable,
+    VariableExpression,
+    operator,
+    unique_variable,
+)
+
+
+class ProverParseError(Exception):
+    pass
+
+
+def get_domain(goal, assumptions):
+    if goal is None:
+        all_expressions = assumptions
+    else:
+        all_expressions = assumptions + [-goal]
+    return reduce(operator.or_, (a.constants() for a in all_expressions), set())
+
+
+class ClosedDomainProver(ProverCommandDecorator):
+    """
+    This is a prover decorator that adds domain closure assumptions before
+    proving.
+    """
+
+    def assumptions(self):
+        assumptions = [a for a in self._command.assumptions()]
+        goal = self._command.goal()
+        domain = get_domain(goal, assumptions)
+        return [self.replace_quants(ex, domain) for ex in assumptions]
+
+    def goal(self):
+        goal = self._command.goal()
+        domain = get_domain(goal, self._command.assumptions())
+        return self.replace_quants(goal, domain)
+
+    def replace_quants(self, ex, domain):
+        """
+        Apply the closed domain assumption to the expression
+
+        - Domain = union([e.free()|e.constants() for e in all_expressions])
+        - translate "exists x.P" to "(z=d1 | z=d2 | ... ) & P.replace(x,z)" OR
+                    "P.replace(x, d1) | P.replace(x, d2) | ..."
+        - translate "all x.P" to "P.replace(x, d1) & P.replace(x, d2) & ..."
+
+        :param ex: ``Expression``
+        :param domain: set of {Variable}s
+        :return: ``Expression``
+        """
+        if isinstance(ex, AllExpression):
+            conjuncts = [
+                ex.term.replace(ex.variable, VariableExpression(d)) for d in domain
+            ]
+            conjuncts = [self.replace_quants(c, domain) for c in conjuncts]
+            return reduce(lambda x, y: x & y, conjuncts)
+        elif isinstance(ex, BooleanExpression):
+            return ex.__class__(
+                self.replace_quants(ex.first, domain),
+                self.replace_quants(ex.second, domain),
+            )
+        elif isinstance(ex, NegatedExpression):
+            return -self.replace_quants(ex.term, domain)
+        elif isinstance(ex, ExistsExpression):
+            disjuncts = [
+                ex.term.replace(ex.variable, VariableExpression(d)) for d in domain
+            ]
+            disjuncts = [self.replace_quants(d, domain) for d in disjuncts]
+            return reduce(lambda x, y: x | y, disjuncts)
+        else:
+            return ex
+
+
+class UniqueNamesProver(ProverCommandDecorator):
+    """
+    This is a prover decorator that adds unique names assumptions before
+    proving.
+    """
+
+    def assumptions(self):
+        """
+        - Domain = union([e.free()|e.constants() for e in all_expressions])
+        - if "d1 = d2" cannot be proven from the premises, then add "d1 != d2"
+        """
+        assumptions = self._command.assumptions()
+
+        domain = list(get_domain(self._command.goal(), assumptions))
+
+        # build a dictionary of obvious equalities
+        eq_sets = SetHolder()
+        for a in assumptions:
+            if isinstance(a, EqualityExpression):
+                av = a.first.variable
+                bv = a.second.variable
+                # put 'a' and 'b' in the same set
+                eq_sets[av].add(bv)
+
+        new_assumptions = []
+        for i, a in enumerate(domain):
+            for b in domain[i + 1 :]:
+                # if a and b are not already in the same equality set
+                if b not in eq_sets[a]:
+                    newEqEx = EqualityExpression(
+                        VariableExpression(a), VariableExpression(b)
+                    )
+                    if Prover9().prove(newEqEx, assumptions):
+                        # we can prove that the names are the same entity.
+                        # remember that they are equal so we don't re-check.
+                        eq_sets[a].add(b)
+                    else:
+                        # we can't prove it, so assume unique names
+                        new_assumptions.append(-newEqEx)
+
+        return assumptions + new_assumptions
+
+
+class SetHolder(list):
+    """
+    A list of sets of Variables.
+    """
+
+    def __getitem__(self, item):
+        """
+        :param item: ``Variable``
+        :return: the set containing 'item'
+        """
+        assert isinstance(item, Variable)
+        for s in self:
+            if item in s:
+                return s
+        # item is not found in any existing set.  so create a new set
+        new = {item}
+        self.append(new)
+        return new
+
+
+class ClosedWorldProver(ProverCommandDecorator):
+    """
+    This is a prover decorator that completes predicates before proving.
+
+    If the assumptions contain "P(A)", then "all x.(P(x) -> (x=A))" is the completion of "P".
+    If the assumptions contain "all x.(ostrich(x) -> bird(x))", then "all x.(bird(x) -> ostrich(x))" is the completion of "bird".
+    If the assumptions don't contain anything that are "P", then "all x.-P(x)" is the completion of "P".
+
+    walk(Socrates)
+    Socrates != Bill
+    + all x.(walk(x) -> (x=Socrates))
+    ----------------
+    -walk(Bill)
+
+    see(Socrates, John)
+    see(John, Mary)
+    Socrates != John
+    John != Mary
+    + all x.all y.(see(x,y) -> ((x=Socrates & y=John) | (x=John & y=Mary)))
+    ----------------
+    -see(Socrates, Mary)
+
+    all x.(ostrich(x) -> bird(x))
+    bird(Tweety)
+    -ostrich(Sam)
+    Sam != Tweety
+    + all x.(bird(x) -> (ostrich(x) | x=Tweety))
+    + all x.-ostrich(x)
+    -------------------
+    -bird(Sam)
+    """
+
+    def assumptions(self):
+        assumptions = self._command.assumptions()
+
+        predicates = self._make_predicate_dict(assumptions)
+
+        new_assumptions = []
+        for p in predicates:
+            predHolder = predicates[p]
+            new_sig = self._make_unique_signature(predHolder)
+            new_sig_exs = [VariableExpression(v) for v in new_sig]
+
+            disjuncts = []
+
+            # Turn the signatures into disjuncts
+            for sig in predHolder.signatures:
+                equality_exs = []
+                for v1, v2 in zip(new_sig_exs, sig):
+                    equality_exs.append(EqualityExpression(v1, v2))
+                disjuncts.append(reduce(lambda x, y: x & y, equality_exs))
+
+            # Turn the properties into disjuncts
+            for prop in predHolder.properties:
+                # replace variables from the signature with new sig variables
+                bindings = {}
+                for v1, v2 in zip(new_sig_exs, prop[0]):
+                    bindings[v2] = v1
+                disjuncts.append(prop[1].substitute_bindings(bindings))
+
+            # make the assumption
+            if disjuncts:
+                # disjuncts exist, so make an implication
+                antecedent = self._make_antecedent(p, new_sig)
+                consequent = reduce(lambda x, y: x | y, disjuncts)
+                accum = ImpExpression(antecedent, consequent)
+            else:
+                # nothing has property 'p'
+                accum = NegatedExpression(self._make_antecedent(p, new_sig))
+
+            # quantify the implication
+            for new_sig_var in new_sig[::-1]:
+                accum = AllExpression(new_sig_var, accum)
+            new_assumptions.append(accum)
+
+        return assumptions + new_assumptions
+
+    def _make_unique_signature(self, predHolder):
+        """
+        This method figures out how many arguments the predicate takes and
+        returns a tuple containing that number of unique variables.
+        """
+        return tuple(unique_variable() for i in range(predHolder.signature_len))
+
+    def _make_antecedent(self, predicate, signature):
+        """
+        Return an application expression with 'predicate' as the predicate
+        and 'signature' as the list of arguments.
+        """
+        antecedent = predicate
+        for v in signature:
+            antecedent = antecedent(VariableExpression(v))
+        return antecedent
+
+    def _make_predicate_dict(self, assumptions):
+        """
+        Create a dictionary of predicates from the assumptions.
+
+        :param assumptions: a list of ``Expression``s
+        :return: dict mapping ``AbstractVariableExpression`` to ``PredHolder``
+        """
+        predicates = defaultdict(PredHolder)
+        for a in assumptions:
+            self._map_predicates(a, predicates)
+        return predicates
+
+    def _map_predicates(self, expression, predDict):
+        if isinstance(expression, ApplicationExpression):
+            func, args = expression.uncurry()
+            if isinstance(func, AbstractVariableExpression):
+                predDict[func].append_sig(tuple(args))
+        elif isinstance(expression, AndExpression):
+            self._map_predicates(expression.first, predDict)
+            self._map_predicates(expression.second, predDict)
+        elif isinstance(expression, AllExpression):
+            # collect all the universally quantified variables
+            sig = [expression.variable]
+            term = expression.term
+            while isinstance(term, AllExpression):
+                sig.append(term.variable)
+                term = term.term
+            if isinstance(term, ImpExpression):
+                if isinstance(term.first, ApplicationExpression) and isinstance(
+                    term.second, ApplicationExpression
+                ):
+                    func1, args1 = term.first.uncurry()
+                    func2, args2 = term.second.uncurry()
+                    if (
+                        isinstance(func1, AbstractVariableExpression)
+                        and isinstance(func2, AbstractVariableExpression)
+                        and sig == [v.variable for v in args1]
+                        and sig == [v.variable for v in args2]
+                    ):
+                        predDict[func2].append_prop((tuple(sig), term.first))
+                        predDict[func1].validate_sig_len(sig)
+
+
+class PredHolder:
+    """
+    This class will be used by a dictionary that will store information
+    about predicates to be used by the ``ClosedWorldProver``.
+
+    The 'signatures' property is a list of tuples defining signatures for
+    which the predicate is true.  For instance, 'see(john, mary)' would be
+    result in the signature '(john,mary)' for 'see'.
+
+    The second element of the pair is a list of pairs such that the first
+    element of the pair is a tuple of variables and the second element is an
+    expression of those variables that makes the predicate true.  For instance,
+    'all x.all y.(see(x,y) -> know(x,y))' would result in "((x,y),('see(x,y)'))"
+    for 'know'.
+    """
+
+    def __init__(self):
+        self.signatures = []
+        self.properties = []
+        self.signature_len = None
+
+    def append_sig(self, new_sig):
+        self.validate_sig_len(new_sig)
+        self.signatures.append(new_sig)
+
+    def append_prop(self, new_prop):
+        self.validate_sig_len(new_prop[0])
+        self.properties.append(new_prop)
+
+    def validate_sig_len(self, new_sig):
+        if self.signature_len is None:
+            self.signature_len = len(new_sig)
+        elif self.signature_len != len(new_sig):
+            raise Exception("Signature lengths do not match")
+
+    def __str__(self):
+        return f"({self.signatures},{self.properties},{self.signature_len})"
+
+    def __repr__(self):
+        return "%s" % self
+
+
+def closed_domain_demo():
+    lexpr = Expression.fromstring
+
+    p1 = lexpr(r"exists x.walk(x)")
+    p2 = lexpr(r"man(Socrates)")
+    c = lexpr(r"walk(Socrates)")
+    prover = Prover9Command(c, [p1, p2])
+    print(prover.prove())
+    cdp = ClosedDomainProver(prover)
+    print("assumptions:")
+    for a in cdp.assumptions():
+        print("   ", a)
+    print("goal:", cdp.goal())
+    print(cdp.prove())
+
+    p1 = lexpr(r"exists x.walk(x)")
+    p2 = lexpr(r"man(Socrates)")
+    p3 = lexpr(r"-walk(Bill)")
+    c = lexpr(r"walk(Socrates)")
+    prover = Prover9Command(c, [p1, p2, p3])
+    print(prover.prove())
+    cdp = ClosedDomainProver(prover)
+    print("assumptions:")
+    for a in cdp.assumptions():
+        print("   ", a)
+    print("goal:", cdp.goal())
+    print(cdp.prove())
+
+    p1 = lexpr(r"exists x.walk(x)")
+    p2 = lexpr(r"man(Socrates)")
+    p3 = lexpr(r"-walk(Bill)")
+    c = lexpr(r"walk(Socrates)")
+    prover = Prover9Command(c, [p1, p2, p3])
+    print(prover.prove())
+    cdp = ClosedDomainProver(prover)
+    print("assumptions:")
+    for a in cdp.assumptions():
+        print("   ", a)
+    print("goal:", cdp.goal())
+    print(cdp.prove())
+
+    p1 = lexpr(r"walk(Socrates)")
+    p2 = lexpr(r"walk(Bill)")
+    c = lexpr(r"all x.walk(x)")
+    prover = Prover9Command(c, [p1, p2])
+    print(prover.prove())
+    cdp = ClosedDomainProver(prover)
+    print("assumptions:")
+    for a in cdp.assumptions():
+        print("   ", a)
+    print("goal:", cdp.goal())
+    print(cdp.prove())
+
+    p1 = lexpr(r"girl(mary)")
+    p2 = lexpr(r"dog(rover)")
+    p3 = lexpr(r"all x.(girl(x) -> -dog(x))")
+    p4 = lexpr(r"all x.(dog(x) -> -girl(x))")
+    p5 = lexpr(r"chase(mary, rover)")
+    c = lexpr(r"exists y.(dog(y) & all x.(girl(x) -> chase(x,y)))")
+    prover = Prover9Command(c, [p1, p2, p3, p4, p5])
+    print(prover.prove())
+    cdp = ClosedDomainProver(prover)
+    print("assumptions:")
+    for a in cdp.assumptions():
+        print("   ", a)
+    print("goal:", cdp.goal())
+    print(cdp.prove())
+
+
+def unique_names_demo():
+    lexpr = Expression.fromstring
+
+    p1 = lexpr(r"man(Socrates)")
+    p2 = lexpr(r"man(Bill)")
+    c = lexpr(r"exists x.exists y.(x != y)")
+    prover = Prover9Command(c, [p1, p2])
+    print(prover.prove())
+    unp = UniqueNamesProver(prover)
+    print("assumptions:")
+    for a in unp.assumptions():
+        print("   ", a)
+    print("goal:", unp.goal())
+    print(unp.prove())
+
+    p1 = lexpr(r"all x.(walk(x) -> (x = Socrates))")
+    p2 = lexpr(r"Bill = William")
+    p3 = lexpr(r"Bill = Billy")
+    c = lexpr(r"-walk(William)")
+    prover = Prover9Command(c, [p1, p2, p3])
+    print(prover.prove())
+    unp = UniqueNamesProver(prover)
+    print("assumptions:")
+    for a in unp.assumptions():
+        print("   ", a)
+    print("goal:", unp.goal())
+    print(unp.prove())
+
+
+def closed_world_demo():
+    lexpr = Expression.fromstring
+
+    p1 = lexpr(r"walk(Socrates)")
+    p2 = lexpr(r"(Socrates != Bill)")
+    c = lexpr(r"-walk(Bill)")
+    prover = Prover9Command(c, [p1, p2])
+    print(prover.prove())
+    cwp = ClosedWorldProver(prover)
+    print("assumptions:")
+    for a in cwp.assumptions():
+        print("   ", a)
+    print("goal:", cwp.goal())
+    print(cwp.prove())
+
+    p1 = lexpr(r"see(Socrates, John)")
+    p2 = lexpr(r"see(John, Mary)")
+    p3 = lexpr(r"(Socrates != John)")
+    p4 = lexpr(r"(John != Mary)")
+    c = lexpr(r"-see(Socrates, Mary)")
+    prover = Prover9Command(c, [p1, p2, p3, p4])
+    print(prover.prove())
+    cwp = ClosedWorldProver(prover)
+    print("assumptions:")
+    for a in cwp.assumptions():
+        print("   ", a)
+    print("goal:", cwp.goal())
+    print(cwp.prove())
+
+    p1 = lexpr(r"all x.(ostrich(x) -> bird(x))")
+    p2 = lexpr(r"bird(Tweety)")
+    p3 = lexpr(r"-ostrich(Sam)")
+    p4 = lexpr(r"Sam != Tweety")
+    c = lexpr(r"-bird(Sam)")
+    prover = Prover9Command(c, [p1, p2, p3, p4])
+    print(prover.prove())
+    cwp = ClosedWorldProver(prover)
+    print("assumptions:")
+    for a in cwp.assumptions():
+        print("   ", a)
+    print("goal:", cwp.goal())
+    print(cwp.prove())
+
+
+def combination_prover_demo():
+    lexpr = Expression.fromstring
+
+    p1 = lexpr(r"see(Socrates, John)")
+    p2 = lexpr(r"see(John, Mary)")
+    c = lexpr(r"-see(Socrates, Mary)")
+    prover = Prover9Command(c, [p1, p2])
+    print(prover.prove())
+    command = ClosedDomainProver(UniqueNamesProver(ClosedWorldProver(prover)))
+    for a in command.assumptions():
+        print(a)
+    print(command.prove())
+
+
+def default_reasoning_demo():
+    lexpr = Expression.fromstring
+
+    premises = []
+
+    # define taxonomy
+    premises.append(lexpr(r"all x.(elephant(x)        -> animal(x))"))
+    premises.append(lexpr(r"all x.(bird(x)            -> animal(x))"))
+    premises.append(lexpr(r"all x.(dove(x)            -> bird(x))"))
+    premises.append(lexpr(r"all x.(ostrich(x)         -> bird(x))"))
+    premises.append(lexpr(r"all x.(flying_ostrich(x)  -> ostrich(x))"))
+
+    # default properties
+    premises.append(
+        lexpr(r"all x.((animal(x)  & -Ab1(x)) -> -fly(x))")
+    )  # normal animals don't fly
+    premises.append(
+        lexpr(r"all x.((bird(x)    & -Ab2(x)) -> fly(x))")
+    )  # normal birds fly
+    premises.append(
+        lexpr(r"all x.((ostrich(x) & -Ab3(x)) -> -fly(x))")
+    )  # normal ostriches don't fly
+
+    # specify abnormal entities
+    premises.append(lexpr(r"all x.(bird(x)           -> Ab1(x))"))  # flight
+    premises.append(lexpr(r"all x.(ostrich(x)        -> Ab2(x))"))  # non-flying bird
+    premises.append(lexpr(r"all x.(flying_ostrich(x) -> Ab3(x))"))  # flying ostrich
+
+    # define entities
+    premises.append(lexpr(r"elephant(E)"))
+    premises.append(lexpr(r"dove(D)"))
+    premises.append(lexpr(r"ostrich(O)"))
+
+    # print the assumptions
+    prover = Prover9Command(None, premises)
+    command = UniqueNamesProver(ClosedWorldProver(prover))
+    for a in command.assumptions():
+        print(a)
+
+    print_proof("-fly(E)", premises)
+    print_proof("fly(D)", premises)
+    print_proof("-fly(O)", premises)
+
+
+def print_proof(goal, premises):
+    lexpr = Expression.fromstring
+    prover = Prover9Command(lexpr(goal), premises)
+    command = UniqueNamesProver(ClosedWorldProver(prover))
+    print(goal, prover.prove(), command.prove())
+
+
+def demo():
+    closed_domain_demo()
+    unique_names_demo()
+    closed_world_demo()
+    combination_prover_demo()
+    default_reasoning_demo()
+
+
+if __name__ == "__main__":
+    demo()

backend/venv/Lib/site-packages/nltk/inference/prover9.py

@@ -0,0 +1,507 @@
+# Natural Language Toolkit: Interface to the Prover9 Theorem Prover
+#
+# Copyright (C) 2001-2025 NLTK Project
+# Author: Dan Garrette <dhgarrette@gmail.com>
+#         Ewan Klein <ewan@inf.ed.ac.uk>
+#
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+"""
+A theorem prover that makes use of the external 'Prover9' package.
+"""
+
+import os
+import subprocess
+
+import nltk
+from nltk.inference.api import BaseProverCommand, Prover
+from nltk.sem.logic import (
+    AllExpression,
+    AndExpression,
+    EqualityExpression,
+    ExistsExpression,
+    Expression,
+    IffExpression,
+    ImpExpression,
+    NegatedExpression,
+    OrExpression,
+)
+
+#
+# Following is not yet used. Return code for 2 actually realized as 512.
+#
+p9_return_codes = {
+    0: True,
+    1: "(FATAL)",  # A fatal error occurred (user's syntax error).
+    2: False,  # (SOS_EMPTY) Prover9 ran out of things to do
+    #   (sos list exhausted).
+    3: "(MAX_MEGS)",  # The max_megs (memory limit) parameter was exceeded.
+    4: "(MAX_SECONDS)",  # The max_seconds parameter was exceeded.
+    5: "(MAX_GIVEN)",  # The max_given parameter was exceeded.
+    6: "(MAX_KEPT)",  # The max_kept parameter was exceeded.
+    7: "(ACTION)",  # A Prover9 action terminated the search.
+    101: "(SIGSEGV)",  # Prover9 crashed, most probably due to a bug.
+}
+
+
+class Prover9CommandParent:
+    """
+    A common base class used by both ``Prover9Command`` and ``MaceCommand``,
+    which is responsible for maintaining a goal and a set of assumptions,
+    and generating prover9-style input files from them.
+    """
+
+    def print_assumptions(self, output_format="nltk"):
+        """
+        Print the list of the current assumptions.
+        """
+        if output_format.lower() == "nltk":
+            for a in self.assumptions():
+                print(a)
+        elif output_format.lower() == "prover9":
+            for a in convert_to_prover9(self.assumptions()):
+                print(a)
+        else:
+            raise NameError(
+                "Unrecognized value for 'output_format': %s" % output_format
+            )
+
+
+class Prover9Command(Prover9CommandParent, BaseProverCommand):
+    """
+    A ``ProverCommand`` specific to the ``Prover9`` prover.  It contains
+    the a print_assumptions() method that is used to print the list
+    of assumptions in multiple formats.
+    """
+
+    def __init__(self, goal=None, assumptions=None, timeout=60, prover=None):
+        """
+        :param goal: Input expression to prove
+        :type goal: sem.Expression
+        :param assumptions: Input expressions to use as assumptions in
+            the proof.
+        :type assumptions: list(sem.Expression)
+        :param timeout: number of seconds before timeout; set to 0 for
+            no timeout.
+        :type timeout: int
+        :param prover: a prover.  If not set, one will be created.
+        :type prover: Prover9
+        """
+        if not assumptions:
+            assumptions = []
+
+        if prover is not None:
+            assert isinstance(prover, Prover9)
+        else:
+            prover = Prover9(timeout)
+
+        BaseProverCommand.__init__(self, prover, goal, assumptions)
+
+    def decorate_proof(self, proof_string, simplify=True):
+        """
+        :see BaseProverCommand.decorate_proof()
+        """
+        if simplify:
+            return self._prover._call_prooftrans(proof_string, ["striplabels"])[
+                0
+            ].rstrip()
+        else:
+            return proof_string.rstrip()
+
+
+class Prover9Parent:
+    """
+    A common class extended by both ``Prover9`` and ``Mace <mace.Mace>``.
+    It contains the functionality required to convert NLTK-style
+    expressions into Prover9-style expressions.
+    """
+
+    _binary_location = None
+
+    def config_prover9(self, binary_location, verbose=False):
+        if binary_location is None:
+            self._binary_location = None
+            self._prover9_bin = None
+        else:
+            name = "prover9"
+            self._prover9_bin = nltk.internals.find_binary(
+                name,
+                path_to_bin=binary_location,
+                env_vars=["PROVER9"],
+                url="https://www.cs.unm.edu/~mccune/prover9/",
+                binary_names=[name, name + ".exe"],
+                verbose=verbose,
+            )
+            self._binary_location = self._prover9_bin.rsplit(os.path.sep, 1)
+
+    def prover9_input(self, goal, assumptions):
+        """
+        :return: The input string that should be provided to the
+            prover9 binary.  This string is formed based on the goal,
+            assumptions, and timeout value of this object.
+        """
+        s = ""
+
+        if assumptions:
+            s += "formulas(assumptions).\n"
+            for p9_assumption in convert_to_prover9(assumptions):
+                s += "    %s.\n" % p9_assumption
+            s += "end_of_list.\n\n"
+
+        if goal:
+            s += "formulas(goals).\n"
+            s += "    %s.\n" % convert_to_prover9(goal)
+            s += "end_of_list.\n\n"
+
+        return s
+
+    def binary_locations(self):
+        """
+        A list of directories that should be searched for the prover9
+        executables.  This list is used by ``config_prover9`` when searching
+        for the prover9 executables.
+        """
+        return [
+            "/usr/local/bin/prover9",
+            "/usr/local/bin/prover9/bin",
+            "/usr/local/bin",
+            "/usr/bin",
+            "/usr/local/prover9",
+            "/usr/local/share/prover9",
+        ]
+
+    def _find_binary(self, name, verbose=False):
+        binary_locations = self.binary_locations()
+        if self._binary_location is not None:
+            binary_locations += [self._binary_location]
+        return nltk.internals.find_binary(
+            name,
+            searchpath=binary_locations,
+            env_vars=["PROVER9"],
+            url="https://www.cs.unm.edu/~mccune/prover9/",
+            binary_names=[name, name + ".exe"],
+            verbose=verbose,
+        )
+
+    def _call(self, input_str, binary, args=[], verbose=False):
+        """
+        Call the binary with the given input.
+
+        :param input_str: A string whose contents are used as stdin.
+        :param binary: The location of the binary to call
+        :param args: A list of command-line arguments.
+        :return: A tuple (stdout, returncode)
+        :see: ``config_prover9``
+        """
+        if verbose:
+            print("Calling:", binary)
+            print("Args:", args)
+            print("Input:\n", input_str, "\n")
+
+        # Call prover9 via a subprocess
+        cmd = [binary] + args
+        try:
+            input_str = input_str.encode("utf8")
+        except AttributeError:
+            pass
+        p = subprocess.Popen(
+            cmd, stdout=subprocess.PIPE, stderr=subprocess.STDOUT, stdin=subprocess.PIPE
+        )
+        (stdout, stderr) = p.communicate(input=input_str)
+
+        if verbose:
+            print("Return code:", p.returncode)
+            if stdout:
+                print("stdout:\n", stdout, "\n")
+            if stderr:
+                print("stderr:\n", stderr, "\n")
+
+        return (stdout.decode("utf-8"), p.returncode)
+
+
+def convert_to_prover9(input):
+    """
+    Convert a ``logic.Expression`` to Prover9 format.
+    """
+    if isinstance(input, list):
+        result = []
+        for s in input:
+            try:
+                result.append(_convert_to_prover9(s.simplify()))
+            except:
+                print("input %s cannot be converted to Prover9 input syntax" % input)
+                raise
+        return result
+    else:
+        try:
+            return _convert_to_prover9(input.simplify())
+        except:
+            print("input %s cannot be converted to Prover9 input syntax" % input)
+            raise
+
+
+def _convert_to_prover9(expression):
+    """
+    Convert ``logic.Expression`` to Prover9 formatted string.
+    """
+    if isinstance(expression, ExistsExpression):
+        return (
+            "exists "
+            + str(expression.variable)
+            + " "
+            + _convert_to_prover9(expression.term)
+        )
+    elif isinstance(expression, AllExpression):
+        return (
+            "all "
+            + str(expression.variable)
+            + " "
+            + _convert_to_prover9(expression.term)
+        )
+    elif isinstance(expression, NegatedExpression):
+        return "-(" + _convert_to_prover9(expression.term) + ")"
+    elif isinstance(expression, AndExpression):
+        return (
+            "("
+            + _convert_to_prover9(expression.first)
+            + " & "
+            + _convert_to_prover9(expression.second)
+            + ")"
+        )
+    elif isinstance(expression, OrExpression):
+        return (
+            "("
+            + _convert_to_prover9(expression.first)
+            + " | "
+            + _convert_to_prover9(expression.second)
+            + ")"
+        )
+    elif isinstance(expression, ImpExpression):
+        return (
+            "("
+            + _convert_to_prover9(expression.first)
+            + " -> "
+            + _convert_to_prover9(expression.second)
+            + ")"
+        )
+    elif isinstance(expression, IffExpression):
+        return (
+            "("
+            + _convert_to_prover9(expression.first)
+            + " <-> "
+            + _convert_to_prover9(expression.second)
+            + ")"
+        )
+    elif isinstance(expression, EqualityExpression):
+        return (
+            "("
+            + _convert_to_prover9(expression.first)
+            + " = "
+            + _convert_to_prover9(expression.second)
+            + ")"
+        )
+    else:
+        return str(expression)
+
+
+class Prover9(Prover9Parent, Prover):
+    _prover9_bin = None
+    _prooftrans_bin = None
+
+    def __init__(self, timeout=60):
+        self._timeout = timeout
+        """The timeout value for prover9.  If a proof can not be found
+           in this amount of time, then prover9 will return false.
+           (Use 0 for no timeout.)"""
+
+    def _prove(self, goal=None, assumptions=None, verbose=False):
+        """
+        Use Prover9 to prove a theorem.
+        :return: A pair whose first element is a boolean indicating if the
+        proof was successful (i.e. returns value of 0) and whose second element
+        is the output of the prover.
+        """
+        if not assumptions:
+            assumptions = []
+
+        stdout, returncode = self._call_prover9(
+            self.prover9_input(goal, assumptions), verbose=verbose
+        )
+        return (returncode == 0, stdout)
+
+    def prover9_input(self, goal, assumptions):
+        """
+        :see: Prover9Parent.prover9_input
+        """
+        s = "clear(auto_denials).\n"  # only one proof required
+        return s + Prover9Parent.prover9_input(self, goal, assumptions)
+
+    def _call_prover9(self, input_str, args=[], verbose=False):
+        """
+        Call the ``prover9`` binary with the given input.
+
+        :param input_str: A string whose contents are used as stdin.
+        :param args: A list of command-line arguments.
+        :return: A tuple (stdout, returncode)
+        :see: ``config_prover9``
+        """
+        if self._prover9_bin is None:
+            self._prover9_bin = self._find_binary("prover9", verbose)
+
+        updated_input_str = ""
+        if self._timeout > 0:
+            updated_input_str += "assign(max_seconds, %d).\n\n" % self._timeout
+        updated_input_str += input_str
+
+        stdout, returncode = self._call(
+            updated_input_str, self._prover9_bin, args, verbose
+        )
+
+        if returncode not in [0, 2]:
+            errormsgprefix = "%%ERROR:"
+            if errormsgprefix in stdout:
+                msgstart = stdout.index(errormsgprefix)
+                errormsg = stdout[msgstart:].strip()
+            else:
+                errormsg = None
+            if returncode in [3, 4, 5, 6]:
+                raise Prover9LimitExceededException(returncode, errormsg)
+            else:
+                raise Prover9FatalException(returncode, errormsg)
+
+        return stdout, returncode
+
+    def _call_prooftrans(self, input_str, args=[], verbose=False):
+        """
+        Call the ``prooftrans`` binary with the given input.
+
+        :param input_str: A string whose contents are used as stdin.
+        :param args: A list of command-line arguments.
+        :return: A tuple (stdout, returncode)
+        :see: ``config_prover9``
+        """
+        if self._prooftrans_bin is None:
+            self._prooftrans_bin = self._find_binary("prooftrans", verbose)
+
+        return self._call(input_str, self._prooftrans_bin, args, verbose)
+
+
+class Prover9Exception(Exception):
+    def __init__(self, returncode, message):
+        msg = p9_return_codes[returncode]
+        if message:
+            msg += "\n%s" % message
+        Exception.__init__(self, msg)
+
+
+class Prover9FatalException(Prover9Exception):
+    pass
+
+
+class Prover9LimitExceededException(Prover9Exception):
+    pass
+
+
+######################################################################
+# { Tests and Demos
+######################################################################
+
+
+def test_config():
+    a = Expression.fromstring("(walk(j) & sing(j))")
+    g = Expression.fromstring("walk(j)")
+    p = Prover9Command(g, assumptions=[a])
+    p._executable_path = None
+    p.prover9_search = []
+    p.prove()
+    # config_prover9('/usr/local/bin')
+    print(p.prove())
+    print(p.proof())
+
+
+def test_convert_to_prover9(expr):
+    """
+    Test that parsing works OK.
+    """
+    for t in expr:
+        e = Expression.fromstring(t)
+        print(convert_to_prover9(e))
+
+
+def test_prove(arguments):
+    """
+    Try some proofs and exhibit the results.
+    """
+    for goal, assumptions in arguments:
+        g = Expression.fromstring(goal)
+        alist = [Expression.fromstring(a) for a in assumptions]
+        p = Prover9Command(g, assumptions=alist).prove()
+        for a in alist:
+            print("   %s" % a)
+        print(f"|- {g}: {p}\n")
+
+
+arguments = [
+    ("(man(x) <-> (not (not man(x))))", []),
+    ("(not (man(x) & (not man(x))))", []),
+    ("(man(x) | (not man(x)))", []),
+    ("(man(x) & (not man(x)))", []),
+    ("(man(x) -> man(x))", []),
+    ("(not (man(x) & (not man(x))))", []),
+    ("(man(x) | (not man(x)))", []),
+    ("(man(x) -> man(x))", []),
+    ("(man(x) <-> man(x))", []),
+    ("(not (man(x) <-> (not man(x))))", []),
+    ("mortal(Socrates)", ["all x.(man(x) -> mortal(x))", "man(Socrates)"]),
+    ("((all x.(man(x) -> walks(x)) & man(Socrates)) -> some y.walks(y))", []),
+    ("(all x.man(x) -> all x.man(x))", []),
+    ("some x.all y.sees(x,y)", []),
+    (
+        "some e3.(walk(e3) & subj(e3, mary))",
+        [
+            "some e1.(see(e1) & subj(e1, john) & some e2.(pred(e1, e2) & walk(e2) & subj(e2, mary)))"
+        ],
+    ),
+    (
+        "some x e1.(see(e1) & subj(e1, x) & some e2.(pred(e1, e2) & walk(e2) & subj(e2, mary)))",
+        [
+            "some e1.(see(e1) & subj(e1, john) & some e2.(pred(e1, e2) & walk(e2) & subj(e2, mary)))"
+        ],
+    ),
+]
+
+expressions = [
+    r"some x y.sees(x,y)",
+    r"some x.(man(x) & walks(x))",
+    r"\x.(man(x) & walks(x))",
+    r"\x y.sees(x,y)",
+    r"walks(john)",
+    r"\x.big(x, \y.mouse(y))",
+    r"(walks(x) & (runs(x) & (threes(x) & fours(x))))",
+    r"(walks(x) -> runs(x))",
+    r"some x.(PRO(x) & sees(John, x))",
+    r"some x.(man(x) & (not walks(x)))",
+    r"all x.(man(x) -> walks(x))",
+]
+
+
+def spacer(num=45):
+    print("-" * num)
+
+
+def demo():
+    print("Testing configuration")
+    spacer()
+    test_config()
+    print()
+    print("Testing conversion to Prover9 format")
+    spacer()
+    test_convert_to_prover9(expressions)
+    print()
+    print("Testing proofs")
+    spacer()
+    test_prove(arguments)
+
+
+if __name__ == "__main__":
+    demo()

backend/venv/Lib/site-packages/nltk/inference/resolution.py

@@ -0,0 +1,759 @@
+# Natural Language Toolkit: First-order Resolution-based Theorem Prover
+#
+# Author: Dan Garrette <dhgarrette@gmail.com>
+#
+# Copyright (C) 2001-2025 NLTK Project
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+Module for a resolution-based First Order theorem prover.
+"""
+
+import operator
+from collections import defaultdict
+from functools import reduce
+
+from nltk.inference.api import BaseProverCommand, Prover
+from nltk.sem import skolemize
+from nltk.sem.logic import (
+    AndExpression,
+    ApplicationExpression,
+    EqualityExpression,
+    Expression,
+    IndividualVariableExpression,
+    NegatedExpression,
+    OrExpression,
+    Variable,
+    VariableExpression,
+    is_indvar,
+    unique_variable,
+)
+
+
+class ProverParseError(Exception):
+    pass
+
+
+class ResolutionProver(Prover):
+    ANSWER_KEY = "ANSWER"
+    _assume_false = True
+
+    def _prove(self, goal=None, assumptions=None, verbose=False):
+        """
+        :param goal: Input expression to prove
+        :type goal: sem.Expression
+        :param assumptions: Input expressions to use as assumptions in the proof
+        :type assumptions: list(sem.Expression)
+        """
+        if not assumptions:
+            assumptions = []
+
+        result = None
+        try:
+            clauses = []
+            if goal:
+                clauses.extend(clausify(-goal))
+            for a in assumptions:
+                clauses.extend(clausify(a))
+            result, clauses = self._attempt_proof(clauses)
+            if verbose:
+                print(ResolutionProverCommand._decorate_clauses(clauses))
+        except RuntimeError as e:
+            if self._assume_false and str(e).startswith(
+                "maximum recursion depth exceeded"
+            ):
+                result = False
+                clauses = []
+            else:
+                if verbose:
+                    print(e)
+                else:
+                    raise e
+        return (result, clauses)
+
+    def _attempt_proof(self, clauses):
+        # map indices to lists of indices, to store attempted unifications
+        tried = defaultdict(list)
+
+        i = 0
+        while i < len(clauses):
+            if not clauses[i].is_tautology():
+                # since we try clauses in order, we should start after the last
+                # index tried
+                if tried[i]:
+                    j = tried[i][-1] + 1
+                else:
+                    j = i + 1  # nothing tried yet for 'i', so start with the next
+
+                while j < len(clauses):
+                    # don't: 1) unify a clause with itself,
+                    #       2) use tautologies
+                    if i != j and j and not clauses[j].is_tautology():
+                        tried[i].append(j)
+                        newclauses = clauses[i].unify(clauses[j])
+                        if newclauses:
+                            for newclause in newclauses:
+                                newclause._parents = (i + 1, j + 1)
+                                clauses.append(newclause)
+                                if not len(newclause):  # if there's an empty clause
+                                    return (True, clauses)
+                            i = -1  # since we added a new clause, restart from the top
+                            break
+                    j += 1
+            i += 1
+        return (False, clauses)
+
+
+class ResolutionProverCommand(BaseProverCommand):
+    def __init__(self, goal=None, assumptions=None, prover=None):
+        """
+        :param goal: Input expression to prove
+        :type goal: sem.Expression
+        :param assumptions: Input expressions to use as assumptions in
+            the proof.
+        :type assumptions: list(sem.Expression)
+        """
+        if prover is not None:
+            assert isinstance(prover, ResolutionProver)
+        else:
+            prover = ResolutionProver()
+
+        BaseProverCommand.__init__(self, prover, goal, assumptions)
+        self._clauses = None
+
+    def prove(self, verbose=False):
+        """
+        Perform the actual proof.  Store the result to prevent unnecessary
+        re-proving.
+        """
+        if self._result is None:
+            self._result, clauses = self._prover._prove(
+                self.goal(), self.assumptions(), verbose
+            )
+            self._clauses = clauses
+            self._proof = ResolutionProverCommand._decorate_clauses(clauses)
+        return self._result
+
+    def find_answers(self, verbose=False):
+        self.prove(verbose)
+
+        answers = set()
+        answer_ex = VariableExpression(Variable(ResolutionProver.ANSWER_KEY))
+        for clause in self._clauses:
+            if (
+                len(clause) == 1
+                and isinstance(clause[0], ApplicationExpression)
+                and clause[0].function == answer_ex
+                and not isinstance(clause[0].argument, IndividualVariableExpression)
+            ):
+                answers.add(clause[0].argument)
+        return answers
+
+    @staticmethod
+    def _decorate_clauses(clauses):
+        """
+        Decorate the proof output.
+        """
+        out = ""
+        max_clause_len = max(len(str(clause)) for clause in clauses)
+        max_seq_len = len(str(len(clauses)))
+        for i in range(len(clauses)):
+            parents = "A"
+            taut = ""
+            if clauses[i].is_tautology():
+                taut = "Tautology"
+            if clauses[i]._parents:
+                parents = str(clauses[i]._parents)
+            parents = " " * (max_clause_len - len(str(clauses[i])) + 1) + parents
+            seq = " " * (max_seq_len - len(str(i + 1))) + str(i + 1)
+            out += f"[{seq}] {clauses[i]} {parents} {taut}\n"
+        return out
+
+
+class Clause(list):
+    def __init__(self, data):
+        list.__init__(self, data)
+        self._is_tautology = None
+        self._parents = None
+
+    def unify(self, other, bindings=None, used=None, skipped=None, debug=False):
+        """
+        Attempt to unify this Clause with the other, returning a list of
+        resulting, unified, Clauses.
+
+        :param other: ``Clause`` with which to unify
+        :param bindings: ``BindingDict`` containing bindings that should be used
+            during the unification
+        :param used: tuple of two lists of atoms.  The first lists the
+            atoms from 'self' that were successfully unified with atoms from
+            'other'.  The second lists the atoms from 'other' that were successfully
+            unified with atoms from 'self'.
+        :param skipped: tuple of two ``Clause`` objects.  The first is a list of all
+            the atoms from the 'self' Clause that have not been unified with
+            anything on the path.  The second is same thing for the 'other' Clause.
+        :param debug: bool indicating whether debug statements should print
+        :return: list containing all the resulting ``Clause`` objects that could be
+            obtained by unification
+        """
+        if bindings is None:
+            bindings = BindingDict()
+        if used is None:
+            used = ([], [])
+        if skipped is None:
+            skipped = ([], [])
+        if isinstance(debug, bool):
+            debug = DebugObject(debug)
+
+        newclauses = _iterate_first(
+            self, other, bindings, used, skipped, _complete_unify_path, debug
+        )
+
+        # remove subsumed clauses.  make a list of all indices of subsumed
+        # clauses, and then remove them from the list
+        subsumed = []
+        for i, c1 in enumerate(newclauses):
+            if i not in subsumed:
+                for j, c2 in enumerate(newclauses):
+                    if i != j and j not in subsumed and c1.subsumes(c2):
+                        subsumed.append(j)
+        result = []
+        for i in range(len(newclauses)):
+            if i not in subsumed:
+                result.append(newclauses[i])
+
+        return result
+
+    def isSubsetOf(self, other):
+        """
+        Return True iff every term in 'self' is a term in 'other'.
+
+        :param other: ``Clause``
+        :return: bool
+        """
+        for a in self:
+            if a not in other:
+                return False
+        return True
+
+    def subsumes(self, other):
+        """
+        Return True iff 'self' subsumes 'other', this is, if there is a
+        substitution such that every term in 'self' can be unified with a term
+        in 'other'.
+
+        :param other: ``Clause``
+        :return: bool
+        """
+        negatedother = []
+        for atom in other:
+            if isinstance(atom, NegatedExpression):
+                negatedother.append(atom.term)
+            else:
+                negatedother.append(-atom)
+
+        negatedotherClause = Clause(negatedother)
+
+        bindings = BindingDict()
+        used = ([], [])
+        skipped = ([], [])
+        debug = DebugObject(False)
+
+        return (
+            len(
+                _iterate_first(
+                    self,
+                    negatedotherClause,
+                    bindings,
+                    used,
+                    skipped,
+                    _subsumes_finalize,
+                    debug,
+                )
+            )
+            > 0
+        )
+
+    def __getslice__(self, start, end):
+        return Clause(list.__getslice__(self, start, end))
+
+    def __sub__(self, other):
+        return Clause([a for a in self if a not in other])
+
+    def __add__(self, other):
+        return Clause(list.__add__(self, other))
+
+    def is_tautology(self):
+        """
+        Self is a tautology if it contains ground terms P and -P.  The ground
+        term, P, must be an exact match, ie, not using unification.
+        """
+        if self._is_tautology is not None:
+            return self._is_tautology
+        for i, a in enumerate(self):
+            if not isinstance(a, EqualityExpression):
+                j = len(self) - 1
+                while j > i:
+                    b = self[j]
+                    if isinstance(a, NegatedExpression):
+                        if a.term == b:
+                            self._is_tautology = True
+                            return True
+                    elif isinstance(b, NegatedExpression):
+                        if a == b.term:
+                            self._is_tautology = True
+                            return True
+                    j -= 1
+        self._is_tautology = False
+        return False
+
+    def free(self):
+        return reduce(operator.or_, ((atom.free() | atom.constants()) for atom in self))
+
+    def replace(self, variable, expression):
+        """
+        Replace every instance of variable with expression across every atom
+        in the clause
+
+        :param variable: ``Variable``
+        :param expression: ``Expression``
+        """
+        return Clause([atom.replace(variable, expression) for atom in self])
+
+    def substitute_bindings(self, bindings):
+        """
+        Replace every binding
+
+        :param bindings: A list of tuples mapping Variable Expressions to the
+            Expressions to which they are bound.
+        :return: ``Clause``
+        """
+        return Clause([atom.substitute_bindings(bindings) for atom in self])
+
+    def __str__(self):
+        return "{" + ", ".join("%s" % item for item in self) + "}"
+
+    def __repr__(self):
+        return "%s" % self
+
+
+def _iterate_first(first, second, bindings, used, skipped, finalize_method, debug):
+    """
+    This method facilitates movement through the terms of 'self'
+    """
+    debug.line(f"unify({first},{second}) {bindings}")
+
+    if not len(first) or not len(second):  # if no more recursions can be performed
+        return finalize_method(first, second, bindings, used, skipped, debug)
+    else:
+        # explore this 'self' atom
+        result = _iterate_second(
+            first, second, bindings, used, skipped, finalize_method, debug + 1
+        )
+
+        # skip this possible 'self' atom
+        newskipped = (skipped[0] + [first[0]], skipped[1])
+        result += _iterate_first(
+            first[1:], second, bindings, used, newskipped, finalize_method, debug + 1
+        )
+
+        try:
+            newbindings, newused, unused = _unify_terms(
+                first[0], second[0], bindings, used
+            )
+            # Unification found, so progress with this line of unification
+            # put skipped and unused terms back into play for later unification.
+            newfirst = first[1:] + skipped[0] + unused[0]
+            newsecond = second[1:] + skipped[1] + unused[1]
+            result += _iterate_first(
+                newfirst,
+                newsecond,
+                newbindings,
+                newused,
+                ([], []),
+                finalize_method,
+                debug + 1,
+            )
+        except BindingException:
+            # the atoms could not be unified,
+            pass
+
+        return result
+
+
+def _iterate_second(first, second, bindings, used, skipped, finalize_method, debug):
+    """
+    This method facilitates movement through the terms of 'other'
+    """
+    debug.line(f"unify({first},{second}) {bindings}")
+
+    if not len(first) or not len(second):  # if no more recursions can be performed
+        return finalize_method(first, second, bindings, used, skipped, debug)
+    else:
+        # skip this possible pairing and move to the next
+        newskipped = (skipped[0], skipped[1] + [second[0]])
+        result = _iterate_second(
+            first, second[1:], bindings, used, newskipped, finalize_method, debug + 1
+        )
+
+        try:
+            newbindings, newused, unused = _unify_terms(
+                first[0], second[0], bindings, used
+            )
+            # Unification found, so progress with this line of unification
+            # put skipped and unused terms back into play for later unification.
+            newfirst = first[1:] + skipped[0] + unused[0]
+            newsecond = second[1:] + skipped[1] + unused[1]
+            result += _iterate_second(
+                newfirst,
+                newsecond,
+                newbindings,
+                newused,
+                ([], []),
+                finalize_method,
+                debug + 1,
+            )
+        except BindingException:
+            # the atoms could not be unified,
+            pass
+
+        return result
+
+
+def _unify_terms(a, b, bindings=None, used=None):
+    """
+    This method attempts to unify two terms.  Two expressions are unifiable
+    if there exists a substitution function S such that S(a) == S(-b).
+
+    :param a: ``Expression``
+    :param b: ``Expression``
+    :param bindings: ``BindingDict`` a starting set of bindings with which
+    the unification must be consistent
+    :return: ``BindingDict`` A dictionary of the bindings required to unify
+    :raise ``BindingException``: If the terms cannot be unified
+    """
+    assert isinstance(a, Expression)
+    assert isinstance(b, Expression)
+
+    if bindings is None:
+        bindings = BindingDict()
+    if used is None:
+        used = ([], [])
+
+    # Use resolution
+    if isinstance(a, NegatedExpression) and isinstance(b, ApplicationExpression):
+        newbindings = most_general_unification(a.term, b, bindings)
+        newused = (used[0] + [a], used[1] + [b])
+        unused = ([], [])
+    elif isinstance(a, ApplicationExpression) and isinstance(b, NegatedExpression):
+        newbindings = most_general_unification(a, b.term, bindings)
+        newused = (used[0] + [a], used[1] + [b])
+        unused = ([], [])
+
+    # Use demodulation
+    elif isinstance(a, EqualityExpression):
+        newbindings = BindingDict([(a.first.variable, a.second)])
+        newused = (used[0] + [a], used[1])
+        unused = ([], [b])
+    elif isinstance(b, EqualityExpression):
+        newbindings = BindingDict([(b.first.variable, b.second)])
+        newused = (used[0], used[1] + [b])
+        unused = ([a], [])
+
+    else:
+        raise BindingException((a, b))
+
+    return newbindings, newused, unused
+
+
+def _complete_unify_path(first, second, bindings, used, skipped, debug):
+    if used[0] or used[1]:  # if bindings were made along the path
+        newclause = Clause(skipped[0] + skipped[1] + first + second)
+        debug.line("  -> New Clause: %s" % newclause)
+        return [newclause.substitute_bindings(bindings)]
+    else:  # no bindings made means no unification occurred.  so no result
+        debug.line("  -> End")
+        return []
+
+
+def _subsumes_finalize(first, second, bindings, used, skipped, debug):
+    if not len(skipped[0]) and not len(first):
+        # If there are no skipped terms and no terms left in 'first', then
+        # all of the terms in the original 'self' were unified with terms
+        # in 'other'.  Therefore, there exists a binding (this one) such that
+        # every term in self can be unified with a term in other, which
+        # is the definition of subsumption.
+        return [True]
+    else:
+        return []
+
+
+def clausify(expression):
+    """
+    Skolemize, clausify, and standardize the variables apart.
+    """
+    clause_list = []
+    for clause in _clausify(skolemize(expression)):
+        for free in clause.free():
+            if is_indvar(free.name):
+                newvar = VariableExpression(unique_variable())
+                clause = clause.replace(free, newvar)
+        clause_list.append(clause)
+    return clause_list
+
+
+def _clausify(expression):
+    """
+    :param expression: a skolemized expression in CNF
+    """
+    if isinstance(expression, AndExpression):
+        return _clausify(expression.first) + _clausify(expression.second)
+    elif isinstance(expression, OrExpression):
+        first = _clausify(expression.first)
+        second = _clausify(expression.second)
+        assert len(first) == 1
+        assert len(second) == 1
+        return [first[0] + second[0]]
+    elif isinstance(expression, EqualityExpression):
+        return [Clause([expression])]
+    elif isinstance(expression, ApplicationExpression):
+        return [Clause([expression])]
+    elif isinstance(expression, NegatedExpression):
+        if isinstance(expression.term, ApplicationExpression):
+            return [Clause([expression])]
+        elif isinstance(expression.term, EqualityExpression):
+            return [Clause([expression])]
+    raise ProverParseError()
+
+
+class BindingDict:
+    def __init__(self, binding_list=None):
+        """
+        :param binding_list: list of (``AbstractVariableExpression``, ``AtomicExpression``) to initialize the dictionary
+        """
+        self.d = {}
+
+        if binding_list:
+            for v, b in binding_list:
+                self[v] = b
+
+    def __setitem__(self, variable, binding):
+        """
+        A binding is consistent with the dict if its variable is not already bound, OR if its
+        variable is already bound to its argument.
+
+        :param variable: ``Variable`` The variable to bind
+        :param binding: ``Expression`` The atomic to which 'variable' should be bound
+        :raise BindingException: If the variable cannot be bound in this dictionary
+        """
+        assert isinstance(variable, Variable)
+        assert isinstance(binding, Expression)
+
+        try:
+            existing = self[variable]
+        except KeyError:
+            existing = None
+
+        if not existing or binding == existing:
+            self.d[variable] = binding
+        elif isinstance(binding, IndividualVariableExpression):
+            # Since variable is already bound, try to bind binding to variable
+            try:
+                existing = self[binding.variable]
+            except KeyError:
+                existing = None
+
+            binding2 = VariableExpression(variable)
+
+            if not existing or binding2 == existing:
+                self.d[binding.variable] = binding2
+            else:
+                raise BindingException(
+                    "Variable %s already bound to another " "value" % (variable)
+                )
+        else:
+            raise BindingException(
+                "Variable %s already bound to another " "value" % (variable)
+            )
+
+    def __getitem__(self, variable):
+        """
+        Return the expression to which 'variable' is bound
+        """
+        assert isinstance(variable, Variable)
+
+        intermediate = self.d[variable]
+        while intermediate:
+            try:
+                intermediate = self.d[intermediate]
+            except KeyError:
+                return intermediate
+
+    def __contains__(self, item):
+        return item in self.d
+
+    def __add__(self, other):
+        """
+        :param other: ``BindingDict`` The dict with which to combine self
+        :return: ``BindingDict`` A new dict containing all the elements of both parameters
+        :raise BindingException: If the parameter dictionaries are not consistent with each other
+        """
+        try:
+            combined = BindingDict()
+            for v in self.d:
+                combined[v] = self.d[v]
+            for v in other.d:
+                combined[v] = other.d[v]
+            return combined
+        except BindingException as e:
+            raise BindingException(
+                "Attempting to add two contradicting "
+                "BindingDicts: '%s' and '%s'" % (self, other)
+            ) from e
+
+    def __len__(self):
+        return len(self.d)
+
+    def __str__(self):
+        data_str = ", ".join(f"{v}: {self.d[v]}" for v in sorted(self.d.keys()))
+        return "{" + data_str + "}"
+
+    def __repr__(self):
+        return "%s" % self
+
+
+def most_general_unification(a, b, bindings=None):
+    """
+    Find the most general unification of the two given expressions
+
+    :param a: ``Expression``
+    :param b: ``Expression``
+    :param bindings: ``BindingDict`` a starting set of bindings with which the
+                     unification must be consistent
+    :return: a list of bindings
+    :raise BindingException: if the Expressions cannot be unified
+    """
+    if bindings is None:
+        bindings = BindingDict()
+
+    if a == b:
+        return bindings
+    elif isinstance(a, IndividualVariableExpression):
+        return _mgu_var(a, b, bindings)
+    elif isinstance(b, IndividualVariableExpression):
+        return _mgu_var(b, a, bindings)
+    elif isinstance(a, ApplicationExpression) and isinstance(b, ApplicationExpression):
+        return most_general_unification(
+            a.function, b.function, bindings
+        ) + most_general_unification(a.argument, b.argument, bindings)
+    raise BindingException((a, b))
+
+
+def _mgu_var(var, expression, bindings):
+    if var.variable in expression.free() | expression.constants():
+        raise BindingException((var, expression))
+    else:
+        return BindingDict([(var.variable, expression)]) + bindings
+
+
+class BindingException(Exception):
+    def __init__(self, arg):
+        if isinstance(arg, tuple):
+            Exception.__init__(self, "'%s' cannot be bound to '%s'" % arg)
+        else:
+            Exception.__init__(self, arg)
+
+
+class UnificationException(Exception):
+    def __init__(self, a, b):
+        Exception.__init__(self, f"'{a}' cannot unify with '{b}'")
+
+
+class DebugObject:
+    def __init__(self, enabled=True, indent=0):
+        self.enabled = enabled
+        self.indent = indent
+
+    def __add__(self, i):
+        return DebugObject(self.enabled, self.indent + i)
+
+    def line(self, line):
+        if self.enabled:
+            print("    " * self.indent + line)
+
+
+def testResolutionProver():
+    resolution_test(r"man(x)")
+    resolution_test(r"(man(x) -> man(x))")
+    resolution_test(r"(man(x) -> --man(x))")
+    resolution_test(r"-(man(x) and -man(x))")
+    resolution_test(r"(man(x) or -man(x))")
+    resolution_test(r"(man(x) -> man(x))")
+    resolution_test(r"-(man(x) and -man(x))")
+    resolution_test(r"(man(x) or -man(x))")
+    resolution_test(r"(man(x) -> man(x))")
+    resolution_test(r"(man(x) iff man(x))")
+    resolution_test(r"-(man(x) iff -man(x))")
+    resolution_test("all x.man(x)")
+    resolution_test("-all x.some y.F(x,y) & some x.all y.(-F(x,y))")
+    resolution_test("some x.all y.sees(x,y)")
+
+    p1 = Expression.fromstring(r"all x.(man(x) -> mortal(x))")
+    p2 = Expression.fromstring(r"man(Socrates)")
+    c = Expression.fromstring(r"mortal(Socrates)")
+    print(f"{p1}, {p2} |- {c}: {ResolutionProver().prove(c, [p1, p2])}")
+
+    p1 = Expression.fromstring(r"all x.(man(x) -> walks(x))")
+    p2 = Expression.fromstring(r"man(John)")
+    c = Expression.fromstring(r"some y.walks(y)")
+    print(f"{p1}, {p2} |- {c}: {ResolutionProver().prove(c, [p1, p2])}")
+
+    p = Expression.fromstring(r"some e1.some e2.(believe(e1,john,e2) & walk(e2,mary))")
+    c = Expression.fromstring(r"some e0.walk(e0,mary)")
+    print(f"{p} |- {c}: {ResolutionProver().prove(c, [p])}")
+
+
+def resolution_test(e):
+    f = Expression.fromstring(e)
+    t = ResolutionProver().prove(f)
+    print(f"|- {f}: {t}")
+
+
+def test_clausify():
+    lexpr = Expression.fromstring
+
+    print(clausify(lexpr("P(x) | Q(x)")))
+    print(clausify(lexpr("(P(x) & Q(x)) | R(x)")))
+    print(clausify(lexpr("P(x) | (Q(x) & R(x))")))
+    print(clausify(lexpr("(P(x) & Q(x)) | (R(x) & S(x))")))
+
+    print(clausify(lexpr("P(x) | Q(x) | R(x)")))
+    print(clausify(lexpr("P(x) | (Q(x) & R(x)) | S(x)")))
+
+    print(clausify(lexpr("exists x.P(x) | Q(x)")))
+
+    print(clausify(lexpr("-(-P(x) & Q(x))")))
+    print(clausify(lexpr("P(x) <-> Q(x)")))
+    print(clausify(lexpr("-(P(x) <-> Q(x))")))
+    print(clausify(lexpr("-(all x.P(x))")))
+    print(clausify(lexpr("-(some x.P(x))")))
+
+    print(clausify(lexpr("some x.P(x)")))
+    print(clausify(lexpr("some x.all y.P(x,y)")))
+    print(clausify(lexpr("all y.some x.P(x,y)")))
+    print(clausify(lexpr("all z.all y.some x.P(x,y,z)")))
+    print(clausify(lexpr("all x.(all y.P(x,y) -> -all y.(Q(x,y) -> R(x,y)))")))
+
+
+def demo():
+    test_clausify()
+    print()
+    testResolutionProver()
+    print()
+
+    p = Expression.fromstring("man(x)")
+    print(ResolutionProverCommand(p, [p]).prove())
+
+
+if __name__ == "__main__":
+    demo()

backend/venv/Lib/site-packages/nltk/inference/tableau.py

@@ -0,0 +1,712 @@
+# Natural Language Toolkit: First-Order Tableau Theorem Prover
+#
+# Copyright (C) 2001-2025 NLTK Project
+# Author: Dan Garrette <dhgarrette@gmail.com>
+#
+# URL: <https://www.nltk.org/>
+# For license information, see LICENSE.TXT
+
+"""
+Module for a tableau-based First Order theorem prover.
+"""
+
+from nltk.inference.api import BaseProverCommand, Prover
+from nltk.internals import Counter
+from nltk.sem.logic import (
+    AbstractVariableExpression,
+    AllExpression,
+    AndExpression,
+    ApplicationExpression,
+    EqualityExpression,
+    ExistsExpression,
+    Expression,
+    FunctionVariableExpression,
+    IffExpression,
+    ImpExpression,
+    LambdaExpression,
+    NegatedExpression,
+    OrExpression,
+    Variable,
+    VariableExpression,
+    unique_variable,
+)
+
+_counter = Counter()
+
+
+class ProverParseError(Exception):
+    pass
+
+
+class TableauProver(Prover):
+    _assume_false = False
+
+    def _prove(self, goal=None, assumptions=None, verbose=False):
+        if not assumptions:
+            assumptions = []
+
+        result = None
+        try:
+            agenda = Agenda()
+            if goal:
+                agenda.put(-goal)
+            agenda.put_all(assumptions)
+            debugger = Debug(verbose)
+            result = self._attempt_proof(agenda, set(), set(), debugger)
+        except RuntimeError as e:
+            if self._assume_false and str(e).startswith(
+                "maximum recursion depth exceeded"
+            ):
+                result = False
+            else:
+                if verbose:
+                    print(e)
+                else:
+                    raise e
+        return (result, "\n".join(debugger.lines))
+
+    def _attempt_proof(self, agenda, accessible_vars, atoms, debug):
+        (current, context), category = agenda.pop_first()
+
+        # if there's nothing left in the agenda, and we haven't closed the path
+        if not current:
+            debug.line("AGENDA EMPTY")
+            return False
+
+        proof_method = {
+            Categories.ATOM: self._attempt_proof_atom,
+            Categories.PROP: self._attempt_proof_prop,
+            Categories.N_ATOM: self._attempt_proof_n_atom,
+            Categories.N_PROP: self._attempt_proof_n_prop,
+            Categories.APP: self._attempt_proof_app,
+            Categories.N_APP: self._attempt_proof_n_app,
+            Categories.N_EQ: self._attempt_proof_n_eq,
+            Categories.D_NEG: self._attempt_proof_d_neg,
+            Categories.N_ALL: self._attempt_proof_n_all,
+            Categories.N_EXISTS: self._attempt_proof_n_some,
+            Categories.AND: self._attempt_proof_and,
+            Categories.N_OR: self._attempt_proof_n_or,
+            Categories.N_IMP: self._attempt_proof_n_imp,
+            Categories.OR: self._attempt_proof_or,
+            Categories.IMP: self._attempt_proof_imp,
+            Categories.N_AND: self._attempt_proof_n_and,
+            Categories.IFF: self._attempt_proof_iff,
+            Categories.N_IFF: self._attempt_proof_n_iff,
+            Categories.EQ: self._attempt_proof_eq,
+            Categories.EXISTS: self._attempt_proof_some,
+            Categories.ALL: self._attempt_proof_all,
+        }[category]
+
+        debug.line((current, context))
+        return proof_method(current, context, agenda, accessible_vars, atoms, debug)
+
+    def _attempt_proof_atom(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        # Check if the branch is closed.  Return 'True' if it is
+        if (current, True) in atoms:
+            debug.line("CLOSED", 1)
+            return True
+
+        if context:
+            if isinstance(context.term, NegatedExpression):
+                current = current.negate()
+            agenda.put(context(current).simplify())
+            return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+        else:
+            # mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
+            agenda.mark_alls_fresh()
+            return self._attempt_proof(
+                agenda,
+                accessible_vars | set(current.args),
+                atoms | {(current, False)},
+                debug + 1,
+            )
+
+    def _attempt_proof_n_atom(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        # Check if the branch is closed.  Return 'True' if it is
+        if (current.term, False) in atoms:
+            debug.line("CLOSED", 1)
+            return True
+
+        if context:
+            if isinstance(context.term, NegatedExpression):
+                current = current.negate()
+            agenda.put(context(current).simplify())
+            return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+        else:
+            # mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
+            agenda.mark_alls_fresh()
+            return self._attempt_proof(
+                agenda,
+                accessible_vars | set(current.term.args),
+                atoms | {(current.term, True)},
+                debug + 1,
+            )
+
+    def _attempt_proof_prop(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        # Check if the branch is closed.  Return 'True' if it is
+        if (current, True) in atoms:
+            debug.line("CLOSED", 1)
+            return True
+
+        # mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
+        agenda.mark_alls_fresh()
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms | {(current, False)}, debug + 1
+        )
+
+    def _attempt_proof_n_prop(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        # Check if the branch is closed.  Return 'True' if it is
+        if (current.term, False) in atoms:
+            debug.line("CLOSED", 1)
+            return True
+
+        # mark all AllExpressions as 'not exhausted' into the agenda since we are (potentially) adding new accessible vars
+        agenda.mark_alls_fresh()
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms | {(current.term, True)}, debug + 1
+        )
+
+    def _attempt_proof_app(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        f, args = current.uncurry()
+        for i, arg in enumerate(args):
+            if not TableauProver.is_atom(arg):
+                ctx = f
+                nv = Variable("X%s" % _counter.get())
+                for j, a in enumerate(args):
+                    ctx = ctx(VariableExpression(nv)) if i == j else ctx(a)
+                if context:
+                    ctx = context(ctx).simplify()
+                ctx = LambdaExpression(nv, ctx)
+                agenda.put(arg, ctx)
+                return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+        raise Exception("If this method is called, there must be a non-atomic argument")
+
+    def _attempt_proof_n_app(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        f, args = current.term.uncurry()
+        for i, arg in enumerate(args):
+            if not TableauProver.is_atom(arg):
+                ctx = f
+                nv = Variable("X%s" % _counter.get())
+                for j, a in enumerate(args):
+                    ctx = ctx(VariableExpression(nv)) if i == j else ctx(a)
+                if context:
+                    # combine new context with existing
+                    ctx = context(ctx).simplify()
+                ctx = LambdaExpression(nv, -ctx)
+                agenda.put(-arg, ctx)
+                return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+        raise Exception("If this method is called, there must be a non-atomic argument")
+
+    def _attempt_proof_n_eq(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        ###########################################################################
+        # Since 'current' is of type '~(a=b)', the path is closed if 'a' == 'b'
+        ###########################################################################
+        if current.term.first == current.term.second:
+            debug.line("CLOSED", 1)
+            return True
+
+        agenda[Categories.N_EQ].add((current, context))
+        current._exhausted = True
+        return self._attempt_proof(
+            agenda,
+            accessible_vars | {current.term.first, current.term.second},
+            atoms,
+            debug + 1,
+        )
+
+    def _attempt_proof_d_neg(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        agenda.put(current.term.term, context)
+        return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_n_all(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        agenda[Categories.EXISTS].add(
+            (ExistsExpression(current.term.variable, -current.term.term), context)
+        )
+        return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_n_some(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        agenda[Categories.ALL].add(
+            (AllExpression(current.term.variable, -current.term.term), context)
+        )
+        return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_and(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        agenda.put(current.first, context)
+        agenda.put(current.second, context)
+        return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_n_or(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        agenda.put(-current.term.first, context)
+        agenda.put(-current.term.second, context)
+        return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_n_imp(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        agenda.put(current.term.first, context)
+        agenda.put(-current.term.second, context)
+        return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_or(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        new_agenda = agenda.clone()
+        agenda.put(current.first, context)
+        new_agenda.put(current.second, context)
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms, debug + 1
+        ) and self._attempt_proof(new_agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_imp(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        new_agenda = agenda.clone()
+        agenda.put(-current.first, context)
+        new_agenda.put(current.second, context)
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms, debug + 1
+        ) and self._attempt_proof(new_agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_n_and(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        new_agenda = agenda.clone()
+        agenda.put(-current.term.first, context)
+        new_agenda.put(-current.term.second, context)
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms, debug + 1
+        ) and self._attempt_proof(new_agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_iff(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        new_agenda = agenda.clone()
+        agenda.put(current.first, context)
+        agenda.put(current.second, context)
+        new_agenda.put(-current.first, context)
+        new_agenda.put(-current.second, context)
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms, debug + 1
+        ) and self._attempt_proof(new_agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_n_iff(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        new_agenda = agenda.clone()
+        agenda.put(current.term.first, context)
+        agenda.put(-current.term.second, context)
+        new_agenda.put(-current.term.first, context)
+        new_agenda.put(current.term.second, context)
+        return self._attempt_proof(
+            agenda, accessible_vars, atoms, debug + 1
+        ) and self._attempt_proof(new_agenda, accessible_vars, atoms, debug + 1)
+
+    def _attempt_proof_eq(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        #########################################################################
+        # Since 'current' is of the form '(a = b)', replace ALL free instances
+        # of 'a' with 'b'
+        #########################################################################
+        agenda.put_atoms(atoms)
+        agenda.replace_all(current.first, current.second)
+        accessible_vars.discard(current.first)
+        agenda.mark_neqs_fresh()
+        return self._attempt_proof(agenda, accessible_vars, set(), debug + 1)
+
+    def _attempt_proof_some(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        new_unique_variable = VariableExpression(unique_variable())
+        agenda.put(current.term.replace(current.variable, new_unique_variable), context)
+        agenda.mark_alls_fresh()
+        return self._attempt_proof(
+            agenda, accessible_vars | {new_unique_variable}, atoms, debug + 1
+        )
+
+    def _attempt_proof_all(
+        self, current, context, agenda, accessible_vars, atoms, debug
+    ):
+        try:
+            current._used_vars
+        except AttributeError:
+            current._used_vars = set()
+
+        # if there are accessible_vars on the path
+        if accessible_vars:
+            # get the set of bound variables that have not be used by this AllExpression
+            bv_available = accessible_vars - current._used_vars
+
+            if bv_available:
+                variable_to_use = list(bv_available)[0]
+                debug.line("--> Using '%s'" % variable_to_use, 2)
+                current._used_vars |= {variable_to_use}
+                agenda.put(
+                    current.term.replace(current.variable, variable_to_use), context
+                )
+                agenda[Categories.ALL].add((current, context))
+                return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+            else:
+                # no more available variables to substitute
+                debug.line("--> Variables Exhausted", 2)
+                current._exhausted = True
+                agenda[Categories.ALL].add((current, context))
+                return self._attempt_proof(agenda, accessible_vars, atoms, debug + 1)
+
+        else:
+            new_unique_variable = VariableExpression(unique_variable())
+            debug.line("--> Using '%s'" % new_unique_variable, 2)
+            current._used_vars |= {new_unique_variable}
+            agenda.put(
+                current.term.replace(current.variable, new_unique_variable), context
+            )
+            agenda[Categories.ALL].add((current, context))
+            agenda.mark_alls_fresh()
+            return self._attempt_proof(
+                agenda, accessible_vars | {new_unique_variable}, atoms, debug + 1
+            )
+
+    @staticmethod
+    def is_atom(e):
+        if isinstance(e, NegatedExpression):
+            e = e.term
+
+        if isinstance(e, ApplicationExpression):
+            for arg in e.args:
+                if not TableauProver.is_atom(arg):
+                    return False
+            return True
+        elif isinstance(e, AbstractVariableExpression) or isinstance(
+            e, LambdaExpression
+        ):
+            return True
+        else:
+            return False
+
+
+class TableauProverCommand(BaseProverCommand):
+    def __init__(self, goal=None, assumptions=None, prover=None):
+        """
+        :param goal: Input expression to prove
+        :type goal: sem.Expression
+        :param assumptions: Input expressions to use as assumptions in
+            the proof.
+        :type assumptions: list(sem.Expression)
+        """
+        if prover is not None:
+            assert isinstance(prover, TableauProver)
+        else:
+            prover = TableauProver()
+
+        BaseProverCommand.__init__(self, prover, goal, assumptions)
+
+
+class Agenda:
+    def __init__(self):
+        self.sets = tuple(set() for i in range(21))
+
+    def clone(self):
+        new_agenda = Agenda()
+        set_list = [s.copy() for s in self.sets]
+
+        new_allExs = set()
+        for allEx, _ in set_list[Categories.ALL]:
+            new_allEx = AllExpression(allEx.variable, allEx.term)
+            try:
+                new_allEx._used_vars = {used for used in allEx._used_vars}
+            except AttributeError:
+                new_allEx._used_vars = set()
+            new_allExs.add((new_allEx, None))
+        set_list[Categories.ALL] = new_allExs
+
+        set_list[Categories.N_EQ] = {
+            (NegatedExpression(n_eq.term), ctx)
+            for (n_eq, ctx) in set_list[Categories.N_EQ]
+        }
+
+        new_agenda.sets = tuple(set_list)
+        return new_agenda
+
+    def __getitem__(self, index):
+        return self.sets[index]
+
+    def put(self, expression, context=None):
+        if isinstance(expression, AllExpression):
+            ex_to_add = AllExpression(expression.variable, expression.term)
+            try:
+                ex_to_add._used_vars = {used for used in expression._used_vars}
+            except AttributeError:
+                ex_to_add._used_vars = set()
+        else:
+            ex_to_add = expression
+        self.sets[self._categorize_expression(ex_to_add)].add((ex_to_add, context))
+
+    def put_all(self, expressions):
+        for expression in expressions:
+            self.put(expression)
+
+    def put_atoms(self, atoms):
+        for atom, neg in atoms:
+            if neg:
+                self[Categories.N_ATOM].add((-atom, None))
+            else:
+                self[Categories.ATOM].add((atom, None))
+
+    def pop_first(self):
+        """Pop the first expression that appears in the agenda"""
+        for i, s in enumerate(self.sets):
+            if s:
+                if i in [Categories.N_EQ, Categories.ALL]:
+                    for ex in s:
+                        try:
+                            if not ex[0]._exhausted:
+                                s.remove(ex)
+                                return (ex, i)
+                        except AttributeError:
+                            s.remove(ex)
+                            return (ex, i)
+                else:
+                    return (s.pop(), i)
+        return ((None, None), None)
+
+    def replace_all(self, old, new):
+        for s in self.sets:
+            for ex, ctx in s:
+                ex.replace(old.variable, new)
+                if ctx is not None:
+                    ctx.replace(old.variable, new)
+
+    def mark_alls_fresh(self):
+        for u, _ in self.sets[Categories.ALL]:
+            u._exhausted = False
+
+    def mark_neqs_fresh(self):
+        for neq, _ in self.sets[Categories.N_EQ]:
+            neq._exhausted = False
+
+    def _categorize_expression(self, current):
+        if isinstance(current, NegatedExpression):
+            return self._categorize_NegatedExpression(current)
+        elif isinstance(current, FunctionVariableExpression):
+            return Categories.PROP
+        elif TableauProver.is_atom(current):
+            return Categories.ATOM
+        elif isinstance(current, AllExpression):
+            return Categories.ALL
+        elif isinstance(current, AndExpression):
+            return Categories.AND
+        elif isinstance(current, OrExpression):
+            return Categories.OR
+        elif isinstance(current, ImpExpression):
+            return Categories.IMP
+        elif isinstance(current, IffExpression):
+            return Categories.IFF
+        elif isinstance(current, EqualityExpression):
+            return Categories.EQ
+        elif isinstance(current, ExistsExpression):
+            return Categories.EXISTS
+        elif isinstance(current, ApplicationExpression):
+            return Categories.APP
+        else:
+            raise ProverParseError("cannot categorize %s" % current.__class__.__name__)
+
+    def _categorize_NegatedExpression(self, current):
+        negated = current.term
+
+        if isinstance(negated, NegatedExpression):
+            return Categories.D_NEG
+        elif isinstance(negated, FunctionVariableExpression):
+            return Categories.N_PROP
+        elif TableauProver.is_atom(negated):
+            return Categories.N_ATOM
+        elif isinstance(negated, AllExpression):
+            return Categories.N_ALL
+        elif isinstance(negated, AndExpression):
+            return Categories.N_AND
+        elif isinstance(negated, OrExpression):
+            return Categories.N_OR
+        elif isinstance(negated, ImpExpression):
+            return Categories.N_IMP
+        elif isinstance(negated, IffExpression):
+            return Categories.N_IFF
+        elif isinstance(negated, EqualityExpression):
+            return Categories.N_EQ
+        elif isinstance(negated, ExistsExpression):
+            return Categories.N_EXISTS
+        elif isinstance(negated, ApplicationExpression):
+            return Categories.N_APP
+        else:
+            raise ProverParseError("cannot categorize %s" % negated.__class__.__name__)
+
+
+class Debug:
+    def __init__(self, verbose, indent=0, lines=None):
+        self.verbose = verbose
+        self.indent = indent
+
+        if not lines:
+            lines = []
+        self.lines = lines
+
+    def __add__(self, increment):
+        return Debug(self.verbose, self.indent + 1, self.lines)
+
+    def line(self, data, indent=0):
+        if isinstance(data, tuple):
+            ex, ctx = data
+            if ctx:
+                data = f"{ex}, {ctx}"
+            else:
+                data = "%s" % ex
+
+            if isinstance(ex, AllExpression):
+                try:
+                    used_vars = "[%s]" % (
+                        ",".join("%s" % ve.variable.name for ve in ex._used_vars)
+                    )
+                    data += ":   %s" % used_vars
+                except AttributeError:
+                    data += ":   []"
+
+        newline = "{}{}".format("   " * (self.indent + indent), data)
+        self.lines.append(newline)
+
+        if self.verbose:
+            print(newline)
+
+
+class Categories:
+    ATOM = 0
+    PROP = 1
+    N_ATOM = 2
+    N_PROP = 3
+    APP = 4
+    N_APP = 5
+    N_EQ = 6
+    D_NEG = 7
+    N_ALL = 8
+    N_EXISTS = 9
+    AND = 10
+    N_OR = 11
+    N_IMP = 12
+    OR = 13
+    IMP = 14
+    N_AND = 15
+    IFF = 16
+    N_IFF = 17
+    EQ = 18
+    EXISTS = 19
+    ALL = 20
+
+
+def testTableauProver():
+    tableau_test("P | -P")
+    tableau_test("P & -P")
+    tableau_test("Q", ["P", "(P -> Q)"])
+    tableau_test("man(x)")
+    tableau_test("(man(x) -> man(x))")
+    tableau_test("(man(x) -> --man(x))")
+    tableau_test("-(man(x) and -man(x))")
+    tableau_test("(man(x) or -man(x))")
+    tableau_test("(man(x) -> man(x))")
+    tableau_test("-(man(x) and -man(x))")
+    tableau_test("(man(x) or -man(x))")
+    tableau_test("(man(x) -> man(x))")
+    tableau_test("(man(x) iff man(x))")
+    tableau_test("-(man(x) iff -man(x))")
+    tableau_test("all x.man(x)")
+    tableau_test("all x.all y.((x = y) -> (y = x))")
+    tableau_test("all x.all y.all z.(((x = y) & (y = z)) -> (x = z))")
+    #    tableau_test('-all x.some y.F(x,y) & some x.all y.(-F(x,y))')
+    #    tableau_test('some x.all y.sees(x,y)')
+
+    p1 = "all x.(man(x) -> mortal(x))"
+    p2 = "man(Socrates)"
+    c = "mortal(Socrates)"
+    tableau_test(c, [p1, p2])
+
+    p1 = "all x.(man(x) -> walks(x))"
+    p2 = "man(John)"
+    c = "some y.walks(y)"
+    tableau_test(c, [p1, p2])
+
+    p = "((x = y) & walks(y))"
+    c = "walks(x)"
+    tableau_test(c, [p])
+
+    p = "((x = y) & ((y = z) & (z = w)))"
+    c = "(x = w)"
+    tableau_test(c, [p])
+
+    p = "some e1.some e2.(believe(e1,john,e2) & walk(e2,mary))"
+    c = "some e0.walk(e0,mary)"
+    tableau_test(c, [p])
+
+    c = "(exists x.exists z3.((x = Mary) & ((z3 = John) & sees(z3,x))) <-> exists x.exists z4.((x = John) & ((z4 = Mary) & sees(x,z4))))"
+    tableau_test(c)
+
+
+#    p = 'some e1.some e2.((believe e1 john e2) and (walk e2 mary))'
+#    c = 'some x.some e3.some e4.((believe e3 x e4) and (walk e4 mary))'
+#    tableau_test(c, [p])
+
+
+def testHigherOrderTableauProver():
+    tableau_test("believe(j, -lie(b))", ["believe(j, -lie(b) & -cheat(b))"])
+    tableau_test("believe(j, lie(b) & cheat(b))", ["believe(j, lie(b))"])
+    tableau_test(
+        "believe(j, lie(b))", ["lie(b)"]
+    )  # how do we capture that John believes all things that are true
+    tableau_test(
+        "believe(j, know(b, cheat(b)))",
+        ["believe(j, know(b, lie(b)) & know(b, steals(b) & cheat(b)))"],
+    )
+    tableau_test("P(Q(y), R(y) & R(z))", ["P(Q(x) & Q(y), R(y) & R(z))"])
+
+    tableau_test("believe(j, cheat(b) & lie(b))", ["believe(j, lie(b) & cheat(b))"])
+    tableau_test("believe(j, -cheat(b) & -lie(b))", ["believe(j, -lie(b) & -cheat(b))"])
+
+
+def tableau_test(c, ps=None, verbose=False):
+    pc = Expression.fromstring(c)
+    pps = [Expression.fromstring(p) for p in ps] if ps else []
+    if not ps:
+        ps = []
+    print(
+        "%s |- %s: %s"
+        % (", ".join(ps), pc, TableauProver().prove(pc, pps, verbose=verbose))
+    )
+
+
+def demo():
+    testTableauProver()
+    testHigherOrderTableauProver()
+
+
+if __name__ == "__main__":
+    demo()