def unifier_atom(expr1: Expression, expr2: Expression):
if (expr2.isAtom()):
expr1, expr2 = expr2, expr1
if (expr1 == expr2):
return []
if (expr2.isVariable()):
expr1, expr2 = expr2, expr1
if (expr1.isVariable()):
if (expr1 in expr2):
return None
if (expr2.isAtom()):
return [[expr1.expression[0], expr2.expression[0]]]
else:
return [[expr1.expression[0], expr2.expression.__str__()]]
return None
def unifier(terms1: Expression, terms2: Expression):
if (terms1.isAtom() or terms2.isAtom()):
return unifier_atom(terms1, terms2)
F1, T1 = terms1.separate()
F2, T2 = terms2.separate()
Z1 = unifier(F1, F2)
if (Z1 == None):
return None
T1.substitute(Z1)
T2.substitute(Z1)
Z2 = unifier(T1, T2)
if (Z2 == None):
return None
Z2 += Z1
return Z2
