class Example4(SimpleStates2):
"""two-state machine with generators and backtracking
"""
# Let the iterator wrap the data in an XIter instance with `appendleft`
# method::
def __iter__(self):
"""Generate and return an iterator
* convert `data` to an iterator queue
* convert the state generators into iterators
* (re) set the state_handler attribute to the init-state
* pass control to the active states state_handler
which should call and process next(self.data_iterator)
"""
self.data_iterator = XIter(self.data) # queue with `appendleft` method
self.high = self.high_handler_generator().__next__
self.low = self.low_handler_generator().__next__
self.state_handler = getattr(self, self.init_state)
# now start the iteration
while True:
yield self.state_handler()
# Add state method generators that use the "backtracking" feature::
def high_handler_generator(self):
"""Return an iterator, whose next() method
returns "h(token)" and switches to `low`, if token > 3
"""
for token in self.data_iterator:
# print( "high got", token )
if token <= 3:
# push back data token
self.data_iterator.appendleft(token)
# set the new state
self.state_handler = self.low
# return non-value indicating the state switch
yield None
else:
yield "h(%d)" % token
#
def low_handler_generator(self):
"""Return an iterator, whose next() method
returns "l(token)" and switches to `high`, if token <=3
"""
for token in self.data_iterator:
# print( "low got", token )
if token > 3:
self.data_iterator.appendleft(token) # push back
# set and run the new state
self.state_handler = self.high
# alternatively, return the token processed by the new
# state handler
yield self.state_handler()
else:
yield "l(%d)" % token
# The `__str__` converter should ignore the switch-indicator::
def __str__(self):
tokens = [token for token in self() if token != None]
return " ".join(tokens)
class Example4(SimpleStates2):
"""two-state machine with generators and backtracking
"""
# Let the iterator wrap the data in an XIter instance with `appendleft`
# method::
def __iter__(self):
"""Generate and return an iterator
* convert `data` to an iterator queue
* convert the state generators into iterators
* (re) set the state_handler attribute to the init-state
* pass control to the active states state_handler
which should call and process next(self.data_iterator)
"""
self.data_iterator = XIter(self.data) # queue with `appendleft` method
self.high = self.high_handler_generator().__next__
self.low = self.low_handler_generator().__next__
self.state_handler = getattr(self, self.init_state)
# now start the iteration
while True:
yield self.state_handler()
# Add state method generators that use the "backtracking" feature::
def high_handler_generator(self):
"""Return an iterator, whose next() method
returns "h(token)" and switches to `low`, if token > 3
"""
for token in self.data_iterator:
# print( "high got", token )
if token <= 3:
# push back data token
self.data_iterator.appendleft(token)
# set the new state
self.state_handler = self.low
# return non-value indicating the state switch
yield None
else:
yield "h(%d)"%token
#
def low_handler_generator(self):
"""Return an iterator, whose next() method
returns "l(token)" and switches to `high`, if token <=3
"""
for token in self.data_iterator:
# print( "low got", token )
if token > 3:
self.data_iterator.appendleft(token) # push back
# set and run the new state
self.state_handler = self.high
# alternatively, return the token processed by the new
# state handler
yield self.state_handler()
else:
yield "l(%d)"%token
# The `__str__` converter should ignore the switch-indicator::
def __str__(self):
tokens = [token for token in self() if token != None]
return " ".join(tokens)
