turing_machine.py

#!/usr/bin/env python
"""
Usage:
  turing_machine.py FILENAME INITIAL
  turing_machine.py FILENAME INITIAL [-r|--rate] [RATE]

Options:
  -h --help
  -r --rate  specify delay rate
"""
import time
import copy
import sys
from docopt import docopt

class TuringMachine(object):
    def __init__(self, filename, initial, rate):
        self.commands = self.parse_file(filename)
        self.tape = list(f"_{initial}_")
        self.rate = float(rate)
        self.place = 1
        self.state = "0"
        self.key = (self.state, self.tape[self.place])
        self.wild_key = (self.state, "*")

    def parse_file(self, filename):
        """Parse turing code from filename into a dict of commands."""
        with open(filename) as f:
            lines = map(str.strip, f.read().splitlines())
            lines = [line for line in lines if not line.startswith(';')]
            lines = map(lambda x: x.split(';')[0].strip().split(' '), lines)
            return dict([(tuple(i[:2]),tuple(i[2:])) for i in lines])

    def visualize(self, tape, place):
        tape_viz = copy.deepcopy(tape)
        tape_viz[place] = f'\033[7m{tape_viz[self.place]}\033[0m'
        print(''.join(tape_viz), end=('\r'
                                      if not self.key[0].startswith("halt")
                                      else ' '))
    def run(self):
        """Run the turing machine."""
        while (self.key in self.commands
               or self.wild_key in self.commands
               and not self.key[0].startswith("halt")):
            # Visualize initial state
            self.visualize(self.tape, self.place)
            # Update rate
            time.sleep(self.rate)
            # Get things to do from hash table
            newchar, action, newstate = (self.commands.get(self.key)
                                         or self.commands[self.wild_key])
            self.tape[self.place] = (newchar
                                     if newchar != '*'
                                     else self.tape[self.place])

            # Update the tape accordingly
            if action == "l":
                self.place = self.place - 1
                if self.place == -1: # Handle moving past beginning
                    self.tape.insert(0,"_")
                    self.place = 0
            elif action == "r":
                self.place = self.place + 1
                if self.place == len(self.tape): # Handle moving past end
                    self.tape.append("_")

            # Update the current state/key/wild
            self.state = newstate
            self.key = (self.state, self.tape[self.place])
            self.wild_key = (self.state, '*')

            # Make visualization
            self.visualize(self.tape, self.place)
        else:
            if not self.key[0].startswith("halt"):
                print(f"No rule for state '{self.state}' "
                      f"and char '{self.tape[self.place]}'.")
            else:
                print('...Done!')

if __name__ == "__main__":
    arguments = docopt(__doc__)
    # print(arguments)
    machine = TuringMachine(
        arguments['FILENAME'],
        arguments['INITIAL'],
        (arguments['RATE'] or .05))
    machine.run()