def deref(self, env):
envValue = env[self]
if not isinstance(envValue, Var): return envValue
next = env.bindings.get(envValue, None)
if next is None: return envValue
if next is self: return next
result = deref(next, env)
if result is not envValue and not isinstance(envValue, RuleHeadCopyVar):
self.setvalue(result, env)
return result
def take_value(self, env):
envValue = env[self]
if not isinstance(envValue, Var):
result = envValue
else:
next = env.bindings.get(envValue, None)
if next is None: result = envValue
elif next is self: result = next
else: result = deref(next, env)
if not isinstance(result, Var):
return take_value(result, env)
return result
def unify(self, other, env, occurs_check=False):
self = self.deref(env)
other = deref(other, env)
if isinstance(self, Var):
if isinstance(other, Var) and other is self:
yield True
return
if occurs_check and contain_var(other, self):return
self.setvalue(other, env)
yield True
try: del env.bindings[self] # for DummyVar
except: pass
elif isinstance(other, Var):
if occurs_check and contain_var(self, other): return
other.setvalue(self, env)
yield True
try: del env.bindings[other] # for DummyVar
except: pass
else:
for result in unify(self, other, env, occurs_check):
yield True
