class TuringMachine:
'''Class to represent a Turing machine'''
def __init__(self, alphabet, initialstate, initialtape, finalstates, blank):
'''Construct a Turing machine
Args:
alphabet (str): The alphabet
initialstate (str): The name of the initial state
initialtape (str): The initial contents of the state
finalstates (List): A list of the names of the final states
blank (str): The blank symbol for this TM
'''
self.alphabet = alphabet
self.initialstate = initialstate
self.states = {}
self.currentstate = self.initialstate
self.tape = Tape(initialtape, blank)
self.finalstates = finalstates
self.halted = ''
self.finaltape = ''
def addstate(self, statename, state):
'''Add a state to the TM
Args:
statename(str) : name of the state
state(State) : the state
'''
self.states[statename] = state
def set_alphabet_in_TM(self,alphabet):
self.alphabet = alphabet
def set_tape_in_TM(self, tape, blank):
self.tape = Tape(tape, blank)
def set_initialstate(self, _state):
self.initialstate = _state
self.currentstate = str(self.initialstate)
def set_finalstates(self, _final):
self.finalstates.add(_final)
# def set_alphabet(self, alphabet):
# self.alphabet = alphabet
#
# def set_initialstate(self, initialstate):
# self.initialstate = initialstate
#
# def add_finalstate(self, statename):
# self.finalstates.append()
def removestate(self, statename):
'''Removes a state from the TM
Args:
statename(str) : name of the state
'''
del self.states[statename]
def getstate(self):
'''Get the current state
Returns:
str: the name of the current state
'''
return self.currentstate
def gettape(self):
'''Get the current tape as a string
Returns:
str: the current tape
'''
return self.tape.gettape()
def step(self):
'''Executes one execution step on the TM
Returns:
bool: False if there was no transition defined, True otherwise
'''
cursym = self.tape.getsym()
state= self.states[self.currentstate]
transition = state.get_transition(cursym)
# print transition
if transition is None:
return False
self.currentstate = transition.get_next_state()
if (transition.get_next_direction() == "R"):
self.tape.writeright(transition.get_write_sym())
else:
self.tape.writeleft(transition.get_write_sym())
return True
class TuringMachine:
'''Class to represent a Turing machine'''
def __init__(self, alphabet, initialstate, initialtape, finalstates, blank):
'''Construct a Turing machine
Args:
alphabet (str): The alphabet
initialstate (str): The name of the initial state
initialtape (str): The initial contents of the state
finalstates (List): A list of the names of the final states
blank (str): The blank symbol for this TM
'''
self.alphabet = alphabet
self.initialstate = initialstate
self.states = {}
self.currentstate = self.initialstate
self.tape = Tape(initialtape, blank)
self.finalstates = finalstates
def addstate(self,statename, state):
'''Add a state to the TM
Args:
statename(str) : name of the state
state(State) : the state
'''
self.states[statename] = state
def getstate(self):
'''Get the current state
Returns:
str: the name of the current state
'''
return self.currentstate
def gettape(self):
'''Get the current tape as a string
Returns:
str: the current tape
'''
return self.tape.gettape()
def step(self):
'''Executes one execution step on the TM
Returns:
bool: False if there was no transition defined, True otherwise
'''
cursym = self.tape.getsym()
state= self.states[self.currentstate]
transition = state.get_transition(cursym)
# print transition
if transition is None:
return False
self.currentstate = transition.get_next_state()
if (transition.get_next_direction() == "R"):
self.tape.writeright(transition.get_write_sym())
else:
self.tape.writeleft(transition.get_write_sym())
return True
def runtohalt(self):
'''Run the machine to completion. Prints an execution trace
Returns:
nothing
'''
print "initial state=", self.currentstate
print "initial tape=", self.gettape()
print " "
steps = 0
while self.step():
steps += 1
print "steps = ", steps
print "state = ", self.currentstate
print "tape = ", self.gettape()
print " "
if self.currentstate in self.finalstates:
print "halted with answer yes"
else:
print "halted with answer no"
