def unify(self, expr):
subs = Substitution()
eqs = [(self, expr)]
while eqs:
lhs, rhs = eqs.pop()
if lhs is rhs:
continue
elif isinstance(lhs, Application) and isinstance(rhs, Application):
eqs.extend(zip(lhs.elems, rhs.elems))
elif isinstance(lhs, Variable) or isinstance(rhs, Variable):
if not isinstance(lhs, Variable):
lhs, rhs = rhs, lhs
if isinstance(rhs, Variable) or not rhs.contains_leaf(lhs):
add_subs = Substitution()
add_subs.replace(lhs, rhs)
subs.compose(add_subs)
eqs = [(add_subs.apply(lhs), add_subs.apply(rhs))
for lhs, rhs in eqs]
else:
return None
else:
return None
return subs
def instantiate_free_variables(self, expr):
vars = expr.collect_variables()
instantiate_vars_subs = Substitution()
for v in vars:
instantiate_vars_subs.replace(v, self.introduce_constant())
return instantiate_vars_subs.apply(expr)
