Subversion Repositories programming

#!/usr/bin/python

#Copyright: Ira W. Snyder

# Start Date: 2005-10-08

# End Date: 

# License: Public Domain

#

# Changelog Follows:

#   -- 2005-10-08 1830

#       Wrote and debugged the entire automaton class

#

import sys, string

class automaton:

    def __init__(self):

        self.__clear()

        self.verbose = False

    def __clear(self):

        self.num_states = 0

        self.num_letters = 0

        self.final_states = []

        self.trans_function = []

    def main_menu(self):

        done = False

        while(not done):

            print "Menu:"

            print "========================================"

            print "1. Enter an automaton"

            print "2. Run automaton"

            print "3. Enable Verbose Mode"

            print "4. Disable Verbose Mode"

            print "5. Quit"

            print

            s = raw_input("Choice >>> ")

            print

            if s == '1':

                self.__clear()

                self.read_automaton()

                print

            elif s == '2':

                input = raw_input("Enter string to test: ")

                self.run_automaton(input)

                print

            elif s == '3':

                self.verbose = True

                print "Verbose Mode Enabled!"

                print

            elif s == '4':

                self.verbose = False

                print "Verbose Mode Disabled!"

                print

            elif s == '5':

                done = True

            else:

                print 'Bad Selection'

                print

    def read_automaton(self):

        done = False

        ### Find out the number of states

        while(not done):

            s = raw_input("How many states?: ")

            try:

                self.num_states = int(s)

                done = True

            except (TypeError, ValueError):

                print "That wasn't an integer, try again!"

                print

        ### Find out what the last letter is

        done = False

        while(not done):

            s = raw_input("What is the last letter?: ")

            if len(s) != 1:

                print "One letter only please, try again!"

                print

            ### Lowercase the input

            s = s.lower()

            for i in range(26):

                if string.letters[i] == s:

                    self.num_letters = i + 1

                    done = True

            if not done:

                print "That was not a letter, try again!"

                print

        ### Find out which states are final states

        done = False

        print

        print "Enter a blank line to stop entering Final States"

        print

        while(not done):

            s = raw_input("Final state: ")

            ### Done reading input

            if len(s) == 0:

                done = True

                break

            if self.check_state(s):

                self.final_states.append(int(s))

            else:

                print "That was not a valid state, try again!"

        ### Read each state / letter pair

        for i in range(self.num_states):

            sublist = []

            for j in range(self.num_letters):

                done = False

                while not done:

                    s = raw_input("Enter state %d, letter %s -> state " % (i, string.letters[j]))

                    if self.check_state(s):

                        sublist.append(int(s))

                        done = True

                    else:

                        print "Not a valid state, try again!"

                        print

            self.trans_function.append(sublist)

        print "Done reading the automaton!"

    def check_state(self, s):

        """Checks the string representing a state to see if it's a valid state.

        Returns True if it is valid, False otherwise"""

        retVal = True

        try:

            state = int(s)

        except (TypeError, ValueError):

            retVal = False

            state = 99999999

        if state >= self.num_states:

            retVal = False

        return retVal

    def get_letter_num(self, s):

        s = s.lower()

        for i in range(26):

            if s == string.letters[i]:

                return i

        return -1

    def next_state(self, cur_state, letter):

        letter_num = self.get_letter_num(letter)

        if letter_num == -1 or letter_num >= self.num_letters:

            print "There was a bad letter in the input"

            print "*** I WILL STAY AT THE CURRENT STATE ***"

            return cur_state

            #sys.exit(1)

        next_state = self.trans_function[cur_state][letter_num]

        if self.verbose:

            print "state %d letter %s -> state %d" % (cur_state, letter, next_state)

        return next_state

    def run_automaton(self, input_string):

        cur_state = 0 #initial state is always q0

        for c in input_string:

            cur_state = self.next_state(cur_state, c)

        print "Done Running"

        print

        print "Final State: %d" % cur_state

        print "Accepted: %s" % (self.is_final_state(cur_state) and "Yes" or "No", )

        print

        print

        s = raw_input('Press ENTER to return to the main menu')

    def is_final_state(self, s):

        """Returns True if s is a final state, False otherwise"""

        retVal = True

        try:

            self.final_states.index(s)

        except ValueError:

            retVal = False

        return retVal

    def enable_verbose(self):

        self.verbose = True

    def disable_verbose(self):

        self.verbose = False

if __name__ == '__main__':

    a = automaton()

    a.main_menu()