Exemplo n.º 1
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    def setUp(self):
        """Set up test fixtures, if any."""
        self.a_sym = Symbol("a")
        self.b_sym = Symbol("b")
        self.c_sym = Symbol("c")
        self.alphabet = Alphabet({self.a_sym, self.b_sym, self.c_sym})

        # Propositions
        self.a = AtomicFormula(self.a_sym)
        self.b = AtomicFormula(self.b_sym)
        self.c = AtomicFormula(self.c_sym)

        self.not_a = Not(self.a)
        self.not_a_and_b = And(self.not_a, self.b)
        self.not_a_or_c = Or(self.not_a, self.c)
        self.true = TrueFormula()
        self.false = FalseFormula()

        self.symbol2truth = {
            self.a_sym: True,
            self.b_sym: False,
            self.c_sym: True
        }
        self.I = PLInterpretation(self.alphabet, self.symbol2truth)
        self.PL = PL(self.alphabet)
Exemplo n.º 2
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 def test_to_nnf_allowed_formulas_not_normalized(self):
     a_sym = Symbol("a")
     b_sym = Symbol("b")
     alphabet = Alphabet({a_sym, b_sym})
     a = AtomicFormula(a_sym)
     b = AtomicFormula(b_sym)
     pl = PL(alphabet)
     self.assertEqual(pl.to_nnf(Not(Not(b))), b)
     self.assertEqual(pl.to_nnf(Not(And(a, Not(b)))), Or(Not(a), b))
Exemplo n.º 3
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 def test_to_nnf_derived_formula(self):
     a_sym = Symbol("a")
     b_sym = Symbol("b")
     alphabet = Alphabet({a_sym, b_sym})
     a = AtomicFormula(a_sym)
     b = AtomicFormula(b_sym)
     pl = PL(alphabet)
     self.assertEqual(pl.to_nnf(Not(Or(b, Not(a)))), And(Not(b), a))
     self.assertEqual(pl.to_nnf(Not(Implies(b, Not(a)))), And(b, a))
Exemplo n.º 4
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 def test_expand_formula_allowed_formulas(self):
     a_sym = Symbol("a")
     b_sym = Symbol("b")
     alphabet = Alphabet({a_sym, b_sym})
     a = AtomicFormula(a_sym)
     b = AtomicFormula(b_sym)
     pl = PL(alphabet)
     self.assertEqual(pl.expand_formula(a), a)
     self.assertEqual(pl.expand_formula(Not(b)), Not(b))
     self.assertEqual(pl.expand_formula(And(a, b)), And(a, b))
Exemplo n.º 5
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 def test_find_atomics(self):
     a = Symbol("a")
     b = Symbol("b")
     c = Symbol("c")
     atomic_a = AtomicFormula(a)
     atomic_b = AtomicFormula(b)
     atomic_c = AtomicFormula(c)
     self.assertEqual(
         PL.find_atomics(And(atomic_a, And(atomic_b, atomic_c))),
         {atomic_a, atomic_b, atomic_c})
     self.assertEqual(PL.find_atomics(Or(atomic_a, Or(atomic_b, atomic_c))),
                      {atomic_a, atomic_b, atomic_c})
     self.assertEqual(
         PL.find_atomics(Equivalence(atomic_a, Or(atomic_b, atomic_c))),
         {atomic_a, atomic_b, atomic_c})
Exemplo n.º 6
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    def test_powerset(self):
        a = Symbol("a")
        b = Symbol("b")
        c = Symbol("c")
        d = Symbol("d")
        s = [a,b,c,d]
        true_ps = {
            (),
            (a,),(b,),(c,),(d,),
            (a, b), (a, c), (a, d), (b, c), (b, d), (c, d),
            (a,b,c), (a,b,d), (a,c,d), (b,c,d),
            (a, b, c, d)

        }
        set_true_ps_frozenset = {frozenset(t) for t in true_ps}
        self.assertEqual(set(powerset(s)), set_true_ps_frozenset)
Exemplo n.º 7
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    def test_expand_formula_error(self):
        a_sym = Symbol("a")
        alphabet = Alphabet({a_sym})
        a = Next(AtomicFormula(a_sym))
        pl = PL(alphabet)

        with self.assertRaises(ValueError) as ve:
            pl.expand_formula(a)
Exemplo n.º 8
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 def __init__(self, env):
     super().__init__(env)
     self.row_symbols = [Symbol(r) for r in ["r0", "r1", "r2"]]
     self.dfa = self._build_automata()
     self.goal_reward = 1000
     self.transition_reward = 100
     self.simulator = Simulator(self.dfa)
     self.last_status = None
Exemplo n.º 9
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 def test_is_formula_composed(self):
     a_sym = Symbol("a")
     alphabet = Alphabet({a_sym})
     a = AtomicFormula(a_sym)
     pl = PL(alphabet)
     self.assertTrue(
         pl.is_formula(
             Implies(Not(a), And(TrueFormula(), Not(FalseFormula())))))
     self.assertFalse(
         pl.is_formula(
             Implies(Not(a), And(TrueFormula(), Next(FalseFormula())))))
Exemplo n.º 10
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    def setUp(self):
        # Symbols
        self.a_sym = Symbol("a")
        self.b_sym = Symbol("b")
        self.c_sym = Symbol("c")

        # Propositions
        self.a = AtomicFormula(self.a_sym)
        self.b = AtomicFormula(self.b_sym)
        self.c = AtomicFormula(self.c_sym)
        self.alphabet = Alphabet({self.a_sym, self.b_sym, self.c_sym})

        self.ref = REf(self.alphabet)
        self.trace_1_list = [
            {self.a_sym, self.b_sym},
            {self.a_sym, self.c_sym},
            {self.a_sym, self.b_sym},
            {self.a_sym, self.c_sym},
            {self.b_sym, self.c_sym},
        ]
        self.trace_1 = FiniteTrace(self.trace_1_list, self.alphabet)
Exemplo n.º 11
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 def test_expand_formula_derived_formulas(self):
     a_sym = Symbol("a")
     b_sym = Symbol("b")
     alphabet = Alphabet({a_sym, b_sym})
     a = AtomicFormula(a_sym)
     b = AtomicFormula(b_sym)
     # T = Not(And(Not(DUMMY_ATOMIC), DUMMY_ATOMIC))
     # F = And(Not(DUMMY_ATOMIC), DUMMY_ATOMIC)
     T = TrueFormula()
     F = FalseFormula()
     pl = PL(alphabet)
     self.assertEqual(pl.expand_formula(TrueFormula()), T)
     self.assertEqual(pl.expand_formula(FalseFormula()), F)
     self.assertEqual(pl.expand_formula(Or(a, b)), Not(And(Not(a), Not(b))))
     self.assertEqual(pl.expand_formula(Implies(a, b)),
                      Not(And(Not(Not(a)), Not(b))))
     self.assertEqual(pl.expand_formula(Implies(b, a)),
                      Not(And(Not(Not(b)), Not(a))))
     # A === B = (A AND B) OR (NOT A AND NOT B) = NOT( NOT(A AND B) AND NOT(NOT A AND NOT B) )
     self.assertEqual(pl.expand_formula(Equivalence(a, b)),
                      Not(And(Not(And(a, b)), Not(And(Not(a), Not(b))))))
Exemplo n.º 12
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 def test_expand_formula_composed(self):
     a_sym = Symbol("a")
     alphabet = Alphabet({a_sym})
     a = AtomicFormula(a_sym)
     # T = Not(And(Not(DUMMY_ATOMIC), DUMMY_ATOMIC))
     # F = And(Not(DUMMY_ATOMIC), DUMMY_ATOMIC)
     T = TrueFormula()
     F = FalseFormula()
     pl = PL(alphabet)
     self.assertEqual(pl.expand_formula(And(TrueFormula(), FalseFormula())),
                      And(T, F))
     self.assertEqual(pl.expand_formula(Or(TrueFormula(), FalseFormula())),
                      Not(And(Not(T), Not(F))))
     self.assertEqual(
         pl.expand_formula(Implies(TrueFormula(), FalseFormula())),
         Not(And(Not(Not(T)), Not(F))))
     self.assertEqual(
         pl.expand_formula(Equivalence(TrueFormula(), FalseFormula())),
         Not(And(Not(And(T, F)), Not(And(Not(T), Not(F))))))
Exemplo n.º 13
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 def fromString(cls, name:str):
     return Variable(Symbol(name))
Exemplo n.º 14
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 def test_chain(self):
     a_sym, b_sym, c_sym = [Symbol(s) for s in ["a", "b", "c"]]
     a, b, c = [AtomicFormula(s) for s in [a_sym,b_sym,c_sym]]
     and_chain = And.chain([a, b, c])
     self.assertEqual(and_chain, And(a, And(b, And(c, TrueFormula()))))
Exemplo n.º 15
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 def test_is_formula_error(self):
     a_sym = Symbol("a")
     alphabet = Alphabet({a_sym})
     a = Next(AtomicFormula(a_sym))
     pl = PL(alphabet)
     self.assertFalse(pl.is_formula(a))
Exemplo n.º 16
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 def fromStrings(symbol_strings:Set[str]):
     return Alphabet(set(Symbol(s) for s in symbol_strings))
Exemplo n.º 17
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 def test_is_formula_atomic(self):
     a_sym = Symbol("a")
     alphabet = Alphabet({a_sym})
     a = AtomicFormula(a_sym)
     pl = PL(alphabet)
     self.assertTrue(pl.is_formula(a))
Exemplo n.º 18
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    def test_minimal_models(self):
        a = Symbol("a")
        b = Symbol("b")
        c = Symbol("c")
        alphabet = Alphabet({a, b, c})
        pl = PL(alphabet)

        atomic_a = AtomicFormula(a)
        atomic_b = AtomicFormula(b)
        atomic_c = AtomicFormula(c)

        self.assertEqual(
            pl.minimal_models(TrueFormula()),
            {PLInterpretation(alphabet, {
                a: False,
                b: False,
                c: False
            })})
        self.assertEqual(pl.minimal_models(FalseFormula()), set())
        self.assertEqual(
            pl.minimal_models(atomic_a),
            {PLInterpretation(alphabet, {
                a: True,
                b: False,
                c: False
            })})
        self.assertEqual(
            pl.minimal_models(Not(atomic_a)),
            {PLInterpretation(alphabet, {
                a: False,
                b: False,
                c: False
            })})
        self.assertEqual(
            pl.minimal_models(And(atomic_a, atomic_b)),
            {PLInterpretation(alphabet, {
                a: True,
                b: True,
                c: False
            })})
        self.assertEqual(pl.minimal_models(And(atomic_a, Not(atomic_a))),
                         set())
        self.assertEqual(
            pl.minimal_models(Or(atomic_a, atomic_b)), {
                PLInterpretation(alphabet, {
                    a: False,
                    b: True,
                    c: False
                }),
                PLInterpretation(alphabet, {
                    a: True,
                    b: False,
                    c: False
                })
            })
        self.assertEqual(
            pl.minimal_models(And.chain([atomic_a, atomic_b, atomic_c])),
            {PLInterpretation(alphabet, {
                a: True,
                b: True,
                c: True
            })})
Exemplo n.º 19
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    def setUp(self):
        """Set up test fixtures, if any."""
        # Symbols
        self.a_sym = Symbol("a")
        self.b_sym = Symbol("b")
        self.c_sym = Symbol("c")

        # Propositions
        self.a = AtomicFormula(self.a_sym)
        self.b = AtomicFormula(self.b_sym)
        self.c = AtomicFormula(self.c_sym)

        # Propositionals
        self.not_a = Not(self.a)
        self.not_b = Not(self.b)
        self.not_c = Not(self.c)
        self.a_and_b = And(self.a, self.b)
        self.a_and_c = And(self.a, self.c)
        self.b_and_c = And(self.b, self.c)
        self.abc = And(self.a, And(self.b, self.c))
        self.b_or_c = Or(self.b, self.c)
        self.a_or_b = Or(self.a, self.b)
        self.not_abc = Not(And(self.a, And(self.b, self.c)))

        ### Path expression
        # Tests
        self.test_a = PathExpressionTest(self.a)
        self.test_b = PathExpressionTest(self.b)
        self.test_not_a = PathExpressionTest(self.not_a)
        self.test_not_b = PathExpressionTest(self.not_b)
        # Union
        self.path_a_or_b = PathExpressionUnion(self.a, self.b)
        self.path_b_or_c = PathExpressionUnion(self.b, self.c)
        # Sequence
        self.path_seq_a_and_b__a_and_c = PathExpressionSequence(
            self.a_and_b, self.a_and_c)
        self.path_a_or_b__b_or_c = PathExpressionSequence(
            self.path_a_or_b, self.path_b_or_c)
        # Stars
        self.path_b_or_c_star = PathExpressionStar(self.path_b_or_c)
        self.path_not_abc = PathExpressionStar(self.not_abc)

        # Modal connective
        self.eventually_propositional_a_and_b__a_and_c = PathExpressionEventually(
            self.a_and_b, self.a_and_c)
        self.eventually_test_a__c = PathExpressionEventually(
            self.test_a, self.c)
        self.eventually_test_a__b = PathExpressionEventually(
            self.test_a, self.b)
        self.eventually_seq_a_and_b__a_and_c__not_c = PathExpressionEventually(
            self.path_seq_a_and_b__a_and_c, self.not_c)
        self.eventually_seq_a_and_b__a_and_c__c = PathExpressionEventually(
            self.path_seq_a_and_b__a_and_c, self.c)
        self.eventually_b_or_c_star__b_and_c = PathExpressionEventually(
            self.path_b_or_c_star, self.b_and_c)

        self.next_a_and_c = PathExpressionEventually(TrueFormula(),
                                                     self.a_and_c)
        self.liveness_b_and_c = PathExpressionEventually(
            PathExpressionStar(TrueFormula()), self.b_and_c)
        self.liveness_abc = PathExpressionEventually(
            PathExpressionStar(TrueFormula()), self.abc)

        self.always_true__a = PathExpressionAlways(
            PathExpressionStar(TrueFormula()), self.a)
        self.always_true__b_or_c = PathExpressionAlways(
            PathExpressionStar(TrueFormula()), self.b_or_c)

        self.alphabet = Alphabet({self.a_sym, self.b_sym, self.c_sym})
        # Traces
        self.ldlf = LDLf(self.alphabet)
        self.trace_1_list = [
            {self.a_sym, self.b_sym},
            {self.a_sym, self.c_sym},
            {self.a_sym, self.b_sym},
            {self.a_sym, self.c_sym},
            {self.b_sym, self.c_sym},
        ]
        self.trace_1 = FiniteTrace(self.trace_1_list, self.alphabet)
Exemplo n.º 20
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 def _members(self):
     return (Symbol(Symbols.LOGICAL_FALSE.value))
Exemplo n.º 21
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 def __str__(self):
     return str(Symbol(Symbols.LOGICAL_FALSE.value))
Exemplo n.º 22
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 def _members(self):
     return (Symbol(Symbols.END.value))
Exemplo n.º 23
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 def __str__(self):
     return str(Symbol(Symbols.END.value))
Exemplo n.º 24
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    def to_nfa(self, f: Formula):
        # TODO: optimize!!!
        assert self.is_formula(f)
        nnf_f = self.to_nnf(f)

        alphabet = powerset(self.alphabet.symbols)
        initial_states = {frozenset([nnf_f])}
        final_states = {frozenset()}
        delta = set()

        pl, I = PL._from_set_of_propositionals(set(), Alphabet(set()))
        d = self.delta(nnf_f, frozenset(), epsilon=True)
        if pl.truth(d, I):
            final_states.add(frozenset([nnf_f]))

        states = {frozenset(), frozenset([nnf_f])}

        states_changed, delta_changed = True, True
        while states_changed or delta_changed:

            states_changed, delta_changed = False, False
            for actions_set in alphabet:
                states_list = list(states)
                for q in states_list:

                    delta_formulas = [
                        self.delta(subf, actions_set) for subf in q
                    ]
                    atomics = [
                        s for subf in delta_formulas
                        for s in PL.find_atomics(subf)
                    ]

                    symbol2formula = {
                        Symbol(str(f)): f
                        for f in atomics
                        if f != TrueFormula() and f != FalseFormula()
                    }
                    formula2atomic_formulas = {
                        f: AtomicFormula.fromName(str(f))
                        if f != TrueFormula() and f != FalseFormula() else f
                        for f in atomics
                    }
                    transformed_delta_formulas = [
                        self._tranform_delta(f, formula2atomic_formulas)
                        for f in delta_formulas
                    ]
                    conjunctions = And.chain(transformed_delta_formulas)

                    models = frozenset(
                        PL(Alphabet(
                            set(symbol2formula))).minimal_models(conjunctions))
                    if len(models) == 0:
                        continue
                    for min_model in models:
                        q_prime = frozenset({
                            symbol2formula[s]
                            for s in min_model.symbol2truth
                            if min_model.symbol2truth[s]
                        })

                        len_before = len(states)
                        states.add(q_prime)
                        if len(states) == len_before + 1:
                            states_list.append(q_prime)
                            states_changed = True

                        len_before = len(delta)
                        delta.add((q, actions_set, q_prime))
                        if len(delta) == len_before + 1:
                            delta_changed = True

                        # check if q_prime should be added as final state
                        if len(q_prime) == 0:
                            final_states.add(q_prime)
                        else:
                            q_prime_delta_conjunction = And.chain([
                                self.delta(subf, frozenset(), epsilon=True)
                                for subf in q_prime
                            ])
                            pl, I = PL._from_set_of_propositionals(
                                set(), Alphabet(set()))
                            if pl.truth(q_prime_delta_conjunction, I):
                                final_states.add(q_prime)

        return {
            "alphabet": alphabet,
            "states": frozenset(states),
            "initial_states": frozenset(initial_states),
            "transitions": delta,
            "accepting_states": frozenset(final_states)
        }
Exemplo n.º 25
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 def fromName(cls, name: str):
     return cls(Symbol(name))
Exemplo n.º 26
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    def setUp(self):
        """Set up symbols, terms and formulas. Both legal and illegal, according to some FOL system"""

        # Symbols
        self.a_sym = Symbol('a')
        self.b_sym = Symbol('b')
        self.const_sym = ConstantSymbol("Const")
        self.fun_sym = FunctionSymbol("Fun", 3)
        self.predicate_sym = PredicateSymbol("Predicate", 2)
        self.A = PredicateSymbol("A", 1)

        # Terms
        self.a = Variable(self.a_sym)
        self.b = Variable(self.b_sym)
        self.c = Variable.fromString("c")
        self.const = ConstantTerm(self.const_sym)
        self.fun_abc = FunctionTerm(self.fun_sym, self.a, self.b, self.c)

        # Formulas
        self.predicate_ab = PredicateFormula(self.predicate_sym, self.a,
                                             self.b)
        self.predicate_ac = PredicateFormula(self.predicate_sym, self.a,
                                             self.c)
        self.A_a = PredicateFormula(self.A, self.a)
        self.a_equal_a = Equal(self.a, self.a)
        self.b_equal_c = Equal(self.b, self.c)
        self.neg_a_equal_a = Not(self.a_equal_a)
        self.neg_Aa = Not(self.A_a)
        self.Aa_and_b_equal_c = And(self.A_a, self.b_equal_c)
        self.Aa_or_b_equal_c = Or(self.A_a, self.b_equal_c)
        self.Aa_implies_b_equal_c = Implies(self.A_a, self.b_equal_c)
        self.exists_a_predicate_ab = Exists(self.a, self.predicate_ab)
        self.forall_b_exists_a_predicate_ab = ForAll(
            self.b, self.exists_a_predicate_ab)

        # FOL
        self.vars = {self.a, self.b, self.c}
        self.functions = {self.const_sym, self.fun_sym}
        self.predicates = {self.predicate_sym, self.A}

        self.alphabet = FOLAlphabet(self.functions, self.predicates)
        self.myFOL = FOL(self.alphabet)

        # define dummy stuff
        # does not belong to myFOL. They are used for test membership to myFOL
        self.dummy_variable = Variable.fromString(
            "ThisVariableDoesNotBelongToFOLSystem")
        self.dummy_fun_sym = FunctionSymbol(
            "ThisFunctionDoesNotBelongToFOLSystem", 3)
        self.dummy_constant_sym = ConstantSymbol(
            "ThisConstDoesNotBelongToFOLSystem")
        self.dummy_predicate_sym = PredicateSymbol(
            "ThisPredicateDoesNotBelongToFOLSystem", 2)

        self.dummy_fun = FunctionTerm(self.dummy_fun_sym, self.a, self.b,
                                      self.dummy_variable)
        self.dummy_constant = ConstantTerm(self.dummy_constant_sym)

        self.dummy_predicate = PredicateFormula(self.dummy_predicate_sym,
                                                self.a, self.b)
        self.dummy_predicate_only_one_symbol_false = PredicateFormula(
            self.predicate_sym, self.dummy_variable, self.dummy_constant)
        self.dummy_equal = Equal(self.c, self.dummy_constant)
        self.dummy_neg = Not(self.dummy_predicate_only_one_symbol_false)
        self.dummy_and = And(self.dummy_predicate, self.predicate_ab)
        self.dummy_or = Or(self.dummy_predicate_only_one_symbol_false,
                           self.predicate_ac)

        self.dummy_exists = Exists(self.dummy_variable,
                                   self.dummy_predicate_only_one_symbol_false)
        self.dummy_forall = ForAll(self.b, self.dummy_predicate)
Exemplo n.º 27
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    def test_eq(self):
        # Symbols
        self.assertEqual(self.a_sym, self.a_sym)
        self.assertEqual(self.a_sym, Symbol("a"))
        self.assertEqual(self.const_sym, ConstantSymbol("Const"))
        self.assertEqual(self.fun_sym, FunctionSymbol("Fun", 3))
        self.assertEqual(self.predicate_sym, PredicateSymbol("Predicate", 2))

        self.assertNotEqual(self.a_sym, Symbol("c"))
        self.assertNotEqual(self.const_sym, ConstantSymbol("Another_Const"))
        self.assertNotEqual(self.fun_sym, FunctionSymbol("Another_Fun", 3))
        self.assertNotEqual(self.fun_sym, FunctionSymbol("Fun", 2))
        self.assertNotEqual(self.predicate_sym,
                            PredicateSymbol("Another_Predicate", 2))
        self.assertNotEqual(self.predicate_sym,
                            PredicateSymbol("Predicate", 1))

        self.assertNotEqual(self.a_sym, self.fun_sym)
        self.assertNotEqual(self.const_sym, self.fun_sym)

        # Terms
        self.assertEqual(self.a, self.a)
        self.assertEqual(self.a, Variable.fromString("a"))
        self.assertEqual(self.const, ConstantTerm(ConstantSymbol("Const")))
        self.assertEqual(
            self.fun_abc,
            FunctionTerm(FunctionSymbol("Fun", 3), self.a, self.b, self.c))

        self.assertNotEqual(self.a, self.b)
        self.assertNotEqual(self.a, Variable.fromString("c"))
        self.assertNotEqual(self.const,
                            ConstantTerm(ConstantSymbol("Another_Const")))
        self.assertNotEqual(
            self.fun_abc,
            FunctionTerm(FunctionSymbol("Another_Fun", 3), self.a, self.b,
                         self.c))
        self.assertNotEqual(
            self.fun_abc,
            FunctionTerm(FunctionSymbol("Fun", 3), self.a, self.b, self.a))

        self.assertNotEqual(self.a, self.fun_abc)

        # Formulas
        self.assertEqual(
            self.predicate_ab,
            PredicateFormula(PredicateSymbol("Predicate", 2),
                             Variable.fromString("a"),
                             Variable.fromString("b")))
        self.assertEqual(
            self.A_a,
            PredicateFormula(PredicateSymbol("A", 1),
                             Variable.fromString("a")))
        self.assertEqual(
            self.b_equal_c,
            Equal(Variable.fromString("b"), Variable.fromString("c")))
        self.assertEqual(
            self.neg_a_equal_a,
            Not(Equal(Variable.fromString("a"), Variable.fromString("a"))))
        self.assertEqual(
            self.forall_b_exists_a_predicate_ab,
            ForAll(
                Variable.fromString("b"),
                Exists(
                    Variable.fromString("a"),
                    PredicateFormula(PredicateSymbol("Predicate", 2),
                                     Variable.fromString("a"),
                                     Variable.fromString("b")))))

        self.assertNotEqual(
            self.predicate_ab,
            PredicateFormula(PredicateSymbol("Predicate", 2),
                             Variable.fromString("a"),
                             Variable.fromString("c")))
        self.assertNotEqual(
            self.predicate_ab,
            PredicateFormula(PredicateSymbol("Another_Predicate", 2),
                             Variable.fromString("a"),
                             Variable.fromString("c")))
        self.assertNotEqual(
            self.A_a,
            PredicateFormula(PredicateSymbol("A", 1),
                             Variable.fromString("b")))
        self.assertNotEqual(
            self.b_equal_c,
            Equal(Variable.fromString("b"), Variable.fromString("b")))
        self.assertNotEqual(
            self.neg_a_equal_a,
            Not(Equal(Variable.fromString("b"), Variable.fromString("a"))))
        self.assertNotEqual(
            self.forall_b_exists_a_predicate_ab,
            ForAll(
                Variable.fromString("b"),
                Exists(
                    Variable.fromString("a"),
                    PredicateFormula(PredicateSymbol("ANOTHER_PREDICATE", 2),
                                     Variable.fromString("a"),
                                     Variable.fromString("b")))))