def decompose(state):
#Try applying the "decompose" rule
#If successful, returns "True" and the new state
#Otherwise, returns "False" and the original state
eqs = state.equations
subst = state.substitution
first = eqs[0]
remaining = eqs[1:]
lhs = first.left_side
rhs = first.right_side
flag = False
new_eqs = []
if (isinstance(lhs, Constant) and isinstance(rhs, Constant)
and lhs == rhs):
return (True, Unification_state(remaining, subst))
if (topSymbol(lhs, 'e') and topSymbol(rhs, 'e')):
flag = True
new_eqs += [Equation(lhs._arguments[0], rhs._arguments[0])]
new_eqs += [Equation(lhs._arguments[1], rhs._arguments[1])]
if (topSymbol(lhs, 'd') and topSymbol(rhs, 'd')):
flag = True
new_eqs += [Equation(lhs._arguments[0], rhs._arguments[0])]
new_eqs += [Equation(lhs._arguments[1], rhs._arguments[1])]
if (topSymbol(lhs, 'n') and topSymbol(rhs, 'n')):
flag = True
new_eqs += [Equation(lhs._arguments[0], rhs._arguments[0])]
return (flag, Unification_state(new_eqs + remaining, subst))
def test_check_xor_structure():
f = Function("f", 1)
a = Constant("a")
b = Constant("b")
c = Constant("c")
x = Variable("x")
z = Zero()
func = FuncTerm(f, [a])
func1 = FuncTerm(f, [b])
func2 = FuncTerm(f, [c])
func3 = FuncTerm(f, [x])
func4 = xor(func, func1)
func5 = xor(func2, func3)
eq1 = Equation(func, b)
eq2 = Equation(func3, c)
eq3 = Equation(func5, z)
eq4 = Equation(xor(func2, func3), z)
eq5 = Equation(xor(func4, func5), z)
topf: Set[Equation] = {eq1, eq2, eq3, eq5}
print("Testing pick_f with equation set: ", topf)
print("Result pick_f: ", pick_f(topf))
print()
def check_redundancy(rule: RewriteRule, redundancy_rules: List[RewriteRule]):
"""
UNFINISHED
Checks redundancy of a rule against a set of redundancy rules.
"""
for redundancy_rule in redundancy_rules:
hypothesis_unifiers = unif(
{Equation(redundancy_rule.hypothesis, rule.hypothesis)})
conclusion_unifiers = unif(
{Equation(redundancy_rule.conclusion, rule.conclusion)})
if hypothesis_unifiers is not False and conclusion_unifiers is not False:
# If all substitutions in conclusion_unifiers present in hypothesis unifiers, return True
if all(((var, term) in hypothesis_unifiers.subs
for var, term in zip(*conclusion_unifiers.subs))):
return True
for position in fpos(rule.hypothesis)[1:]:
unifiers = unif({
Equation(redundancy_rule.hypothesis,
get_sub_term(rule.hypothesis, position))
})
if unifiers is not False:
return True
return False
def test_pick_fail():
c = Function("C", 3)
f = Function("f", 1)
a = Constant("a")
b = Constant('1')
e = Constant("e")
p = Constant('p')
q = Constant('q')
i = Constant('i')
j = Constant('j')
x = Variable("x")
z = Zero()
func = FuncTerm(f, [a])
func2 = FuncTerm(f, [e])
func_pi = FuncTerm(c, [p, i, b])
func_qj = FuncTerm(c, [q, j, b])
eq1 = Equation(func, z)
eq2 = Equation(func_qj, x)
eq3 = Equation(xor(func_pi, func), z)
eq4 = Equation(xor(xor(func_pi, func), func2), z)
topf: Set[Equation] = {eq1, eq4}
print("Testing pick_fail with ", topf)
new_set = pick_fail(topf, cbc_gen)
print("Result: ", new_set)
print()
topf: Set[Equation] = {eq1, eq2, eq3}
print("Testing pick_fail with ", topf)
new_set = pick_fail(topf, ex4_gen)
print("Result: ", new_set)
print()
def apply(self, state):
#Apply a rule to some equation
#Assume that the N-Decomposition rule is applicable.
#Returns two states
equations = state.equations.contents
disequations = state.disequations.contents
substs = state.substitution
(eq_index, first_term,
second_term) = self.get_equation_and_two_terms(state)
equations1 = equations
equations2 = deepcopy(equations)
equation_to_be_processed = equations1[eq_index]
del equations1[eq_index]
#Remove first_term and second_term from new_equation.
new_term = xor(equation_to_be_processed.left_side,
equation_to_be_processed.right_side)
term_list = xor_to_list(new_term)
new_lhs = []
for t in term_list:
if (t == first_term or t == second_term):
continue
else:
new_lhs.append(t)
if (len(new_lhs) != 0):
new_equation = Equation(list_to_xor(new_lhs), Zero())
else:
new_equation = Equation(Zero(), Zero())
equations1.append(new_equation)
unifier = unif({Equation(first_term, second_term)})
#equations1.append(Equation(xor(first_term.arg, second_term.arg), Zero()))
#if((first_term == second_term) or (unifier.domain() != [])):
# unifiable = True
#else:
# unifiable = False
if (unifier == False):
unifiable = False
else:
unifiable = True
disequations1 = disequations
disequations2 = deepcopy(disequations)
new_disequation = Disequation(first_term, second_term)
disequations2.append(new_disequation)
state2 = XOR_proof_state(Equations(equations2),
Disequations(disequations2), substs)
if (unifiable):
state1 = XOR_proof_state(
apply_sub_to_equations(Equations(equations1), unifier),
apply_sub_to_disequations(Disequations(disequations1),
unifier), substs * unifier)
return (unifiable, state1, state2)
else:
return (unifiable, state, state2)
def overlap(rule1, rule2, rs, position):
"""
UNFINISHED
Overlaps a rule at a position with a second rule, then reduces the
outcome against an initial set of rules.
"""
rule1_copy = deepcopy(rule1)
rule2_copy = deepcopy(rule2)
right = get_sub_term(rule1_copy.conclusion, position)
left = rule2_copy.hypothesis
unifiers = unif({Equation(left, right)})
print("Left", left)
print("Right", right)
print(unifiers)
if unifiers is False:
return False
new_left = deepcopy(rule1_copy.hypothesis)
new_left = new_left * unifiers
new_right = deepcopy(rule1_copy.conclusion)
new_right = replace(new_right, position, rule2_copy.conclusion)
new_right = new_right * unifiers
new_right = normal(new_right, rs)[0]
return RewriteRule(new_left, new_right)
def purify_an_equation(eq, eqs):
(purified_lhs, eqs) = purify_a_term(eq.left_side, eqs)
#eqs = eqs + eqs1
(purified_rhs, eqs) = purify_a_term(eq.right_side, eqs)
#eqs = eqs + eqs2
new_equation = Equation(purified_lhs, purified_rhs)
return (new_equation, eqs)
def normalize_an_equation(eq):
if is_zero(eq.right_side):
lhs = eq.left_side
else:
lhs = xor(eq.left_side, eq.right_side)
lst = xor_to_list(lhs)
lst = simplify(lst)
new_lhs = list_to_xor(lst)
new_rhs = Zero()
new_eq = Equation(new_lhs, new_rhs)
return new_eq
def test_elimf():
f = Function("f", 1)
xo = Function("f", 2)
z = Zero()
c = Constant("c")
x = Variable("x")
b = Variable("b")
func = FuncTerm(f, [x])
func2 = FuncTerm(f, [z])
func3 = FuncTerm(xo, [c, b])
eq1 = Equation(func, c)
eq2 = Equation(xor(func, func3), z)
eq3 = Equation(b, func)
eq4 = Equation(func2, z)
topf: Set[Equation] = {eq1, eq2, eq3, eq4}
print("Testing elim_f with ", topf)
new_set = elim_f(topf)
print("Result ", new_set)
print()
def p_syntactic(l: Term, r: Term, constraints: Dict[Variable, List[Term]]):
"""
p_syntactic is syntactic unification with the assurance
that the unifier satisfies the constraints given.
"""
sigma = unif({Equation(l, r)})
if sigma == False:
return sigma
sigma_domain, sigma_range = zip(*sigma.subs)
for x, y in zip(sigma_domain, sigma_range):
if isinstance(y, FuncTerm) and y not in constraints[x]:
return False
return sigma
def apply(self, state):
eq = self.is_applicable(state)
first = eq.left_side.arguments[0]
second = eq.left_side.arguments[1]
sigma = unif({Equation(first, second)})
if (sigma == False):
return (False, None)
else:
new_eqs = apply_sub_to_equations(state.equations, sigma)
new_eqs = normalize_equations(new_eqs)
state.substitution = state.substitution * sigma
return (True,
XOR_proof_state(new_eqs, state.disequations,
state.substitution))
def test_pick_c():
c = Function("C", 3)
f = Function("f", 1)
a = Constant("a")
b = Constant('1')
p = Constant('p')
q = Constant('q')
i = Constant('i')
j = Constant('j')
x = Variable("x")
z = Zero()
func = FuncTerm(f, [a])
func_pi = FuncTerm(c, [p, i, b])
func_qj = FuncTerm(c, [q, j, b])
eq1 = Equation(func, z)
eq2 = Equation(func_qj, x)
eq3 = Equation(xor(func_pi, func), 0)
topf: Set[Equation] = {eq1, eq2, eq3}
print("Testing pick_c with ", topf)
def _match(self, term: Term) -> Term:
"""Attempts to rewrite the root term with the rewrite rule. Returns the same term if rewriting is not possible"""
# Change common variables in RewriteRule if they exist
overlaping_vars = _getOverlapVars(term, self.hypothesis,
self.conclusion)
while overlaping_vars:
self.hypothesis, self.conclusion = _changeVars(
overlaping_vars, term, self.hypothesis, self.conclusion)
overlaping_vars = _getOverlapVars(term, self.hypothesis,
self.conclusion)
# Perform matching and substitution
frozen_term = freeze(term)
sigma = unify({Equation(self.hypothesis, frozen_term)})
return self.conclusion * sigma if sigma is not False else None
def test_occurs():
f = Function("f", 1)
g = Function("g", 1)
c = Function("C", 3)
p = Constant('p')
q = Constant('q')
i = Constant('i')
z = Variable("z")
x = Variable("x")
y = Variable("y")
b = Variable("b")
a = Variable("a")
cpi = FuncTerm(c, [p, i, Constant("1")])
fcpi = FuncTerm(f, [cpi])
e1 = Equation(cpi, fcpi)
e2 = Equation(x, FuncTerm(f, [g(x)]))
e3 = Equation(x, FuncTerm(f, [b]))
occ = {e1, e2, e3}
print("Testing occurs check with ", occ)
print("new set: ", occurs_check(occ))
print()
def check_security(tag):
if not check_syntax(tag):
print(f"{tag} is not a valid tag.")
return None
lhs = tag
rhs = convertToConstantTerm(lhs)
eq = Equation(lhs, rhs)
subst = SubstituteTerm()
state = Unification_state([eq], subst)
subst = apply_rules(state)
if (trivial_subst(subst)):
print("The authenticity property is satisfied.")
else:
print("The authenticity property is violated.")
def split(state):
#Try applying the "split" rule
#This rule applied if an equation is of the form: s_1 xor e(...) = t_1 xor e(...)
#or s_1 xor d(...) = t_1 xor d(...)
#If successful, returns "True" and the new state
#Otherwise, returns "False" and the original state
#Example: s_1 xor e(...) = t_1 xor e(...); id ==> s_1 = t_1, e(...) xor e(...); id
#Example: s_1 = t_1; id (not applicable)
eqs = state.equations
subst = state.substitution
first = eqs[0]
remaining_eqs = eqs[1:]
lhs = first.left_side
rhs = first.right_side
lhs_summands = summands(lhs)
rhs_summands = summands(rhs)
applicable = containsDorE(lhs_summands)
if (applicable):
(e_term1, others1) = split_terms(lhs_summands)
(e_term2, others2) = split_terms_wrt_term(rhs_summands, e_term1)
eq1 = Equation(e_term1, e_term2)
if (len(others1) == 1):
eq2 = Equation(*others1, *others2)
else:
eq2 = Equation(xor(*others1), xor(*others2))
remaining_eqs.append(eq1)
remaining_eqs.append(eq2)
return (applicable, Unification_state(remaining_eqs, subst))
else:
return (applicable, state)
def test_elimc():
c = Function("C", 3)
p = Constant('p')
q = Constant('q')
i = Constant('i')
j = Constant('j')
a = Constant('1')
x = Variable("x")
z = Zero()
func_pi = FuncTerm(c, [p, i, a])
func_qj = FuncTerm(c, [q, j, a])
eq1 = Equation(xor(func_pi, func_qj), z)
eq2 = Equation(xor(func_qj, func_pi), z)
eq3 = Equation(func_pi, x)
topf: Set[Equation] = {eq1, eq2, eq3}
print("Testing elim_c with ", topf)
new_set = elim_c(topf)
print("Result: ", new_set)
print()
b = Constant('2')
func_pi = FuncTerm(c, [p, i, a])
func_qj = FuncTerm(c, [q, j, b])
eq1 = Equation(xor(func_pi, func_qj), z)
eq2 = Equation(xor(func_qj, func_pi), z)
topf: Set[Equation] = {eq1, eq2}
print("Testing elim_c with ", topf)
new_set = elim_c(topf)
print("Result: ", new_set)
print()
def combine_two_substitutions(subst1, subst2):
#Combine two substitutions, and get a list of combined substitutions.
#For example, if sub1 = {x1 |-> f(x), x2 |-> b}, sub2 = {x1 |-> f(a)},
#then the result would be [{x1 |-> f(a), x2 |-> b}]
#print("combining")
#print(sub1)
#print("and")
#print(sub2)
#print("end")
sub1 = deepcopy(subst1)
sub2 = deepcopy(subst2)
domain1 = list(sub1.domain())
domain2 = list(sub2.domain())
#if(sub2 == None):
if (domain2 == []):
return [sub1]
else:
#domain2 = list(sub2.domain())
first_var_in_sub2 = domain2[0]
first_var_maps_to_in_sub2 = first_var_in_sub2 * sub2
if (first_var_in_sub2 in domain1):
first_var_maps_to_in_sub1 = first_var_in_sub2 * sub1
if (first_var_maps_to_in_sub1 == first_var_maps_to_in_sub2):
#print("duplicate variables map to the same term")
sub2.remove(first_var_in_sub2)
return combine_two_substitutions(sub1, sub2)
else:
#print("duplicate variables map to different terms")
eq = Equation(convert_to_xorterm(first_var_maps_to_in_sub1),
convert_to_xorterm(first_var_maps_to_in_sub2))
eqs = Equations([eq])
unifiers = xor_unification(eqs)
results = []
sub2.remove(first_var_in_sub2)
for unifier in unifiers:
result = combine_two_substitutions(sub1 * unifier,
sub2 * unifier)
results = results + result
return results
else:
#print("no duplicate variables found")
sigma = SubstituteTerm()
sigma.add(first_var_in_sub2, first_var_maps_to_in_sub2)
sub1 = sub1 * sigma
sub2.remove(first_var_in_sub2)
return combine_two_substitutions(sub1, sub2)
def find_collision(cipher_text1: Term,
cipher_text2: Term,
constraints: Dict[Variable, List[Term]],
unif_algo: Callable = p_unif) -> Optional[SubstituteTerm]:
"""
Sets up a unification problem between two ciphertexts in order to see
if there is a possible collision given some constraints.
"""
if unif_algo == p_unif:
unifiers = unif_algo(Equations([Equation(cipher_text1, cipher_text2)]),
constraints)
elif unif_algo == XOR_rooted_security:
unifiers = unif_algo([cipher_text1, cipher_text2], constraints).solve()
elif unif_algo == p_syntactic:
unifiers = unif_algo(cipher_text1, cipher_text2, constraints)
else:
raise ValueError("Unification algorithm provided is not supported.")
return unifiers
def elim_tk(state):
#Try applying the "elim_tk" rule
#This rule applied if an equation is of the form: s_1 xor ... xor s_m = t_1 xor ... xor t_n,
#where no s_i or t_j is d-rooted or e-rooted, and some s_i is a indexed variable Tk.
#Tk = tk; id (applicable)
#Tk xor e(Tk, C1) = tk xor e(tk, c1); id (not applicable)
#If successful, returns "True" and the new state
#Otherwise, returns "False" and the original state
#Example: Tk = tk; id ==> true, ; {Tk |-> tk}
#Example: Tk xor e(Tk, C1) = tk xor e(tk, c1); id ==> false, Tk xor e(Tk, C1) = tk xor e(tk, c1); id
eqs = state.equations
subst = state.substitution
first = eqs[0]
remaining_eqs = eqs[1:]
lhs = first.left_side
rhs = first.right_side
lhs_summands = summands(lhs)
rhs_summands = summands(rhs)
applicable = (not containsDorE(lhs_summands)) and containsT(lhs_summands)
new_subst = SubstituteTerm()
remaining_terms = []
results = []
if (applicable):
(var, remaining_terms) = pickT(lhs_summands)
remaining_terms += rhs_summands
if (len(remaining_terms) == 1):
new_subst.add(var, remaining_terms[0])
else:
new_subst.add(var, xor(*remaining_terms))
for t in remaining_eqs:
results.append(
Equation(t.left_side * new_subst, t.right_side * new_subst))
return (applicable, Unification_state(results, subst * new_subst))
def resolve(constrained_t1, constrained_t2):
#Takes two constrained terms t1[sigma] and t2[tau], apply resolution to them,
#returns a list of all possible results
#For example, if t1 is f(x) + a[y |-> z] and t2 is f(a) + b[y |-> a],
#then the result is a + b[y |-> a]
t1 = convert_to_XORTerm(constrained_t1.term)
constraint1 = constrained_t1.constraint
t2 = convert_to_XORTerm(constrained_t2.term)
constraint2 = constrained_t2.constraint
constraint12 = combine_two_substitutions(constraint1, constraint2)
if (constraint12 == []):
return []
results1 = get_resolution_term_and_remaining_term(t1)
results2 = get_resolution_term_and_remaining_term(t2)
results = []
for (term1, remaining_t1) in results1:
for (term2, remaining_t2) in results2:
eq = Equation(convert_to_xorterm(term1), convert_to_xorterm(term2))
eqs = Equations([eq])
#print("solving:")
#print(eq)
xor_unifiers = xor_unification(eqs)
#print("xor unifiers:")
#for xor_u in xor_unifiers:
# print(xor_u)
for unifier in xor_unifiers:
for cons12 in constraint12:
constraint123 = combine_two_substitutions(unifier, cons12)
for cons123 in constraint123:
remaining_t1 = convert_to_xorterm(remaining_t1)
remaining_t2 = convert_to_xorterm(remaining_t2)
r1 = remaining_t1 * cons123
r2 = remaining_t2 * cons123
r1 = convert_to_XORTerm(r1)
r2 = convert_to_XORTerm(r2)
constraint_term = ConstrainedTerm(
combine_two_XOR_Terms(r1, r2), cons123)
results.append(constraint_term)
return results
def name_xor_terms(t, eqs):
# Purify arguments
# Name top-level xor-subterms
# Return (renamed_term, a set of equations)
if is_zero(t):
return (t, eqs)
elif (isinstance(t, Constant)):
return (t, eqs)
elif (isinstance(t, Variable)):
return (t, eqs)
elif (is_xor_term(t)):
(term1, eqs) = purify_a_term(t.arguments[0], eqs)
#eqs = eqs + equation1
(term2, eqs) = purify_a_term(t.arguments[1], eqs)
#eqs = eqs + equation2
#equations = equation1 + equation2
name = look_up_a_name(xor(term1, term2), eqs)
if (name != None):
return (name, eqs)
else:
global variable_counter
variable_counter += 1
new_variable = Variable("N" + str(variable_counter))
eqs.append(Equation(new_variable, xor(term1, term2)))
return (new_variable, eqs)
elif (isinstance(t, FuncTerm)):
terms = []
for arg in t.arguments:
(term, eqs) = name_xor_terms(arg, eqs)
#eqs = eqs + equations
terms.append(term)
return (FuncTerm(t.function, terms), eqs)
else:
print("error")
return None
a = Constant("a")
b = Constant("b")
c = Constant("c")
d = Constant("d")
zero = Zero()
#The CBC mode is modeled as: [c, x1, t1, x2, t2, ......]
#where t1 = f(xor(c, x1) and t2 = f(xor(x2, t1))
t1 = f(xor(c, x1))
t2 = f(xor(x2, t1))
#The constraints are modeled using a dictionary in Python.
#So x1 can take any term from constraints[x1] and terms built up using "h" and "xor"
#x2 is similar
constraints1 = {x1: [c, zero], x2: [c, zero, x1, t1]}
#trying to unify t1 and t2
eq1 = Equation(t1, t2)
eqs1 = Equations([eq1])
result = p_unif(eqs1, constraints1)
print("Here are the P-unifiers:")
for r in result:
print(r)
#Here is another mode, modeled as [a, x1, f(a), x2, f(x2), x3, b, x4, f(xor(h(f(x1)), f(x4), f(b)))]
''''
t3 = f(x2)
t4 = f(xor(h(f(x1)), f(x4), f(b)))
eq2 = Equation(t3, t4)
eqs2 = Equations([eq2])
#!/usr/bin/env python3
from symcollab.algebra import Function, Variable, Constant, Equation
from symcollab.Unification.unif import unif
# Setting up terms
f = Function("f", 2)
g = Function("g", 1)
x = Variable("x")
y = Variable("y")
z = Variable("z")
a = Constant("a")
b = Constant("b")
# applying unification
#example 1: unifiable
unif({Equation(f(x, y), f(a, b))})
#example 2: simple function clash
unif({Equation(f(x, y), g(z))})
#example 3: function clash
unif({Equation(f(x, x), f(g(y), a))})
#example 4: occurs check
unif({Equation(f(x, y), f(g(x), a))})
#example 5: unifiable
unif({Equation(f(z, z), f(g(f(x, y)), g(f(a, b))))})
from symcollab.algebra import Constant, Function, Variable, Equation
from symcollab.Unification.syntactic_ac_unification import *
#Setup the variables and AC function
f = Function("f", 2)
x = Variable("x")
y = Variable("y")
z = Variable("z")
a = Constant("a")
b = Constant("b")
x1 = Variable("x1")
y1 = Variable("y1")
z1 = Variable("z1")
#Example 1
e = Equation(f(x, y), f(x1, y1))
U = {e}
sol = synt_ac_unif(U) #For a single solution
# also sol = synt_ac)unif(U, True)
sol = synt_ac_unif(U, False) # For all solutions
#Example 2
e = Equation(f(x, x), f(y, y))
U = {e}
sol = synt_ac_unif(U)
#Example 3
e2 = Equation(f(x, x), f(f(y, y), f(z, z)))
U1 = {e2}
sol = synt_ac_unif(U1)
from symcollab.algebra import Constant, Equation, Function, Sort, \
SubstituteTerm, Variable
from symcollab.algebra.dag import TermDAG
# Setting up terms
f = Function("f", 2)
g = Function("g", 2)
x = Variable("x")
y = Variable("y")
z = Variable("z")
a = Constant("a")
b = Constant("b")
c = Constant("c")
# Simple Equation Printing
e1 = Equation(x, a)
e2 = Equation(f(Constant("2"), Constant("2")), Constant("4"))
print(e1)
print(e2)
# Simple sort test
reals = Sort("reals")
non_zeros = Sort("non_zeros", reals)
divide = Function("divide", 2, [reals, non_zeros], reals)
one = Constant("1", non_zeros)
zero = Constant("0", reals)
try:
divide(one, zero)
except Exception:
print("Cannot divide by zero. Check.")
def apply_sub_to_equation(eq, sub):
lhs = eq.left_side
rhs = eq.right_side
return Equation(lhs * sub, rhs * sub)
#eac_unif_ex.py
from symcollab.algebra import Function, Equation, Variable
from symcollab.Unification.eac_unif import eac_unif
exp = Function("exp", 2)
x = Variable("x")
y = Variable("y")
w = Variable("w")
t = exp(x, y)
t2 = exp(x, w)
e1 = Equation(t, t2)
U = set()
U.add(e1)
z = Variable("z")
g = Function("g", 2)
t3 = g(z, z)
t4 = g(w, w)
e2 = Equation(t3, t4)
U.add(e2)
eac_unif(U)
u = Variable("u")
v = Variable("v")
t3 = exp(v, w)
t4 = g(x, y)
e3 = Equation(u, t3)
e4 = Equation(u, t4)
U = set()
U.add(e3)
U.add(e4)
eac_unif(U)
from symcollab.Unification.ac_unif import ac_unify
f = Function("f", 2)
g = Function("g", 1)
x = Variable("x")
y = Variable("y")
z = Variable("z")
a = Constant("a")
b = Constant("b")
t = f(x, x)
s = f(f(y, y), x)
v = f(y, y)
w = f(z, z)
e1 = Equation(s, t)
e2 = Equation(v, w)
U = set()
U.add(e1)
U.add(e2)
U2 = set()
U2.add(e1)
ac_unify(U)
ac_unify(U2)
from symcollab.algebra import Constant, Function, Variable, Equation
from symcollab.Unification.ac_unif import ac_unify
f = Function("f", 2)
