-
Notifications
You must be signed in to change notification settings - Fork 0
/
tmsim.py
390 lines (333 loc) · 10.8 KB
/
tmsim.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
#!/usr/bin/env python
"""
## ################################################################################ ##
## Name:
## Turing Machine Simulator
##
## Description:
## Runs a Turing Machine using multiple infinite tapes and one pointer
## per tape.
##
## Author:
## Calvin M.T. (calvinmt.com)
## ################################################################################ ##
"""
import sys
import argparse
DEBUGGING = False
VERBOSING = False
OPTION_DEBUG = "-d"
STEP_CURRENT_STATE = 'Q'
STEP_MOVE = 'm'
STEP_NEXT_STATE = 'N'
STEP_READ = 'r'
STEP_WRITE = 'w'
WILDCARD_ALL = '*'
WILDCARD_ALL_BUT_BLANK = '~'
MOVE_LEFT = "L"
MOVE_RIGHT = "R"
COMMENT_CHARACTER = '#'
# ########## ########## ########## #
# MACHINE STRUCTURE
#
# <blank_character>
# <returned_characters>
# <initial_state>
# <final_state>
# <machine_syntax>
# <machine_rules>
#
# Example:
#
# B
# |X
# q0
# halt
# Q r w m N
# q0 | B R q1
# q0 B X - halt
# q1 | | - halt
# q1 B B - halt
#
# ########## ########## ########## #
stepIndexCurrentState = -1
stepIndexMove = -1
stepIndexNextState = -1
stepIndexRead = -1
stepIndexWrite = -1
blankCharacter = ""
returnedCharacters = []
initialState = ""
finalState = ""
rules = []
pointers = []
tapes = []
def prepareStepIndices(syntax):
"""
Order the Turing Machine's execution of a rule depending on the given syntax.
:param syntax: list of characters
:return: None
"""
global stepIndexCurrentState
global stepIndexMove
global stepIndexNextState
global stepIndexRead
global stepIndexWrite
stepIndexCurrentState = -1
stepIndexMove = -1
stepIndexNextState = -1
stepIndexRead = -1
stepIndexWrite = -1
for i in range(len(syntax)):
step = syntax[i]
if step == STEP_CURRENT_STATE:
stepIndexCurrentState = i
elif step == STEP_MOVE:
stepIndexMove = i
elif step == STEP_NEXT_STATE:
stepIndexNextState = i
elif step == STEP_READ:
stepIndexRead = i
elif step == STEP_WRITE:
stepIndexWrite = i
else:
sys.exit("ERROR: unknown step in syntax (" + syntax[i] + ")")
if stepIndexCurrentState <= -1 or stepIndexRead <= -1:
sys.exit("ERROR: syntax needs a current state (" + STEP_CURRENT_STATE + ") and a read (" + STEP_READ + ")")
def readRules(machineFile):
"""
Read the instance of a Turing Machine file with the file pointer starting on its rules to create a list of rules.
:param machineFile: Turing Machine file instance
:return: list of rules
"""
rules = []
STATE_NORMAL = 0
STATE_PARENTHESIS = 1
state = STATE_NORMAL
p = 0
i = 0
for line in machineFile:
if len(line) <= 1:
continue
line = line.rstrip('\n')
if i == len(rules):
rules.append([])
rules[i].append([""])
step = 0
for c in line:
if c == COMMENT_CHARACTER and state == STATE_NORMAL:
break
elif c == ' ' and state == STATE_NORMAL:
rules[i].append([""])
step += 1
elif c == ' ' and state == STATE_PARENTHESIS:
continue
elif c == '(' and state == STATE_NORMAL:
state = STATE_PARENTHESIS
elif c == '(' and state == STATE_PARENTHESIS:
sys.exit("ERROR: nested parentheses not supported in rules")
elif c == ')' and state == STATE_NORMAL:
sys.exit("ERROR: nested parentheses not supported in rules")
elif c == ')' and state == STATE_PARENTHESIS:
state = STATE_NORMAL
p = 0
elif c == ',' and state == STATE_PARENTHESIS:
rules[i][step].append("")
p += 1
else:
rules[i][step][p] = rules[i][step][p] + c
if len(rules[i][0][0]) > 0:
i += 1
return rules
def readTapes(tapeFile):
"""
Read the instance of a tape file to create a list of tapes and a list of their pointers.
:param tapeFile: tape file instance
:return: list of tapes, list of pointers
"""
pointers = []
tapes = []
STATE_IDLE = 0
STATE_READING_TAPE = 1
state = STATE_IDLE
for line in tapeFile:
line = line.rstrip('\n')
tape = []
for c in line:
if c == COMMENT_CHARACTER:
state = STATE_IDLE
break
else:
if state != STATE_READING_TAPE:
state == STATE_READING_TAPE
pointers.append(0)
tape.append(c)
if len(tape) > 0:
tapes.append(tape)
state = STATE_IDLE
tapeFile.close()
return tapes, pointers
def nextFileLine(machineFile, processEmptyLines=True):
line = machineFile.readline().rstrip('\n')
while (processEmptyLines and len(line) == 0) or (len(line) != 0 and line[0] == COMMENT_CHARACTER):
line = machineFile.readline().rstrip('\n')
return line
def prepareMachine(machinePath, tapePath):
"""
Read Turing Machine file and tape file to set and initialise blank character, returning characters, initial state,
final state, rules, pointers and tapes.
:param machinePath: Turing Machine file
:param tapePath: tape file
:return: None
"""
global blankCharacter
global returnedCharacters
global initialState
global finalState
global rules
global pointers
global tapes
machineFile = open(machinePath, 'r')
line = nextFileLine(machineFile)
blankCharacter = line[0]
line = nextFileLine(machineFile, False)
returnedCharacters = line
line = nextFileLine(machineFile)
initialState = line
line = nextFileLine(machineFile)
finalState = line
line = nextFileLine(machineFile)
syntax = line.replace(" ", "")
rules = readRules(machineFile)
machineFile.close()
DEBUG("Blank character:\t" + blankCharacter)
DEBUG("Returned characters:\t" + returnedCharacters)
DEBUG("Initial state:\t\t" + initialState)
DEBUG("Final state:\t\t" + finalState)
DEBUG("Syntax:\t\t\t" + str(syntax))
DEBUG("")
prepareStepIndices(syntax)
tapeFile = open(tapePath, 'r')
tapes, pointers = readTapes(tapeFile)
tapeFile.close()
def findStateIndices(state):
"""
Search through the list of rules for the ones for which their beginning state matches state.
:param state: beginning state
:return: list of rule indices
"""
result = []
for i in range(len(rules)):
if rules[i][stepIndexCurrentState][0] == state:
result.append(i)
if len(result) == 0:
sys.exit("ERROR: no state found (" + state + ")")
return result
def findStateUniqueIndex(state):
"""
Search through the list of rules for the one for which its beginning state matches current state and its reading
characters match currently pointed characters from each tape.
:param state: beginning state
:return: rule index
"""
result = -1
stateIndices = findStateIndices(state)
for i in stateIndices:
count = 0
for j in range(len(tapes)):
readCharacter = tapes[j][pointers[j]]
if rules[i][stepIndexRead][j] == readCharacter or \
rules[i][stepIndexRead][j] == WILDCARD_ALL or \
(rules[i][stepIndexRead][j] == WILDCARD_ALL_BUT_BLANK and readCharacter != blankCharacter):
count += 1
if count == len(tapes):
if result > -1:
sys.exit("ERROR: non-unique rule (" + state + ", " + str(rules[i][stepIndexRead]) + ")")
result = i
if result <= -1:
characters = []
for i in range(len(tapes)):
characters.append(tapes[i][pointers[i]])
sys.exit("ERROR: no rule found (" + state + ", " + str(characters) + ")")
return result
def runRule(currentState):
"""
Run a single rule for which its beginning state matches current state and its read characters match currently
pointed characters from each tape.
:param currentState: beginning state
:return: next state
"""
global pointers
nextState = currentState
currentStateIndex = findStateUniqueIndex(currentState)
for i, tape in enumerate(tapes):
if stepIndexWrite > -1:
if rules[currentStateIndex][stepIndexWrite][i] != WILDCARD_ALL and \
rules[currentStateIndex][stepIndexWrite][i] != WILDCARD_ALL_BUT_BLANK:
tape[pointers[i]] = rules[currentStateIndex][stepIndexWrite][i]
if stepIndexMove > -1:
stepMove = rules[currentStateIndex][stepIndexMove][i]
if stepMove == MOVE_LEFT:
pointers[i] -= 1
if pointers[i] == -1:
tape.insert(0, blankCharacter)
pointers[i] = 0
if stepMove == MOVE_RIGHT:
pointers[i] += 1
if pointers[i] == len(tape):
tape.append(blankCharacter)
if stepIndexNextState > -1:
nextState = rules[currentStateIndex][stepIndexNextState][0]
return nextState
def computeResult():
"""
Count the number of returning characters for each tape.
:return: None
"""
if len(returnedCharacters) > 0:
for i in range(len(tapes)):
print("Tape", i)
for r in returnedCharacters:
counter = 0
for c in tapes[i]:
if c == r:
counter += 1
print("\t", r, ":", counter)
def runMachine():
"""
Run the prepared Turing Machine.
:return: None
"""
currentState = initialState
while currentState != finalState:
DEBUG(STEP_CURRENT_STATE + ": " + currentState + ";\tpointer: " + str(pointers))
VERBOSE(tapes)
if DEBUGGING and VERBOSING:
print()
currentState = runRule(currentState)
DEBUG(STEP_CURRENT_STATE + ": " + currentState + ";\tpointer: " + str(pointers))
if not VERBOSING:
DEBUG("")
print(tapes)
def DEBUG(string):
if DEBUGGING:
print(string)
def VERBOSE(string):
if VERBOSING:
print(string)
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='Turing Machine Simulator')
parser.add_argument('-d', '--debug', action='store_true', help='Enable debug display')
parser.add_argument('-v', '--verbose', action='store_true', help='Enable verbose display')
parser.add_argument('machine')
parser.add_argument('tape')
args = parser.parse_args()
DEBUGGING = args.debug
VERBOSING = args.verbose
machinePath = args.machine
tapePath = args.tape
prepareMachine(machinePath, tapePath)
runMachine()
if len(returnedCharacters) > 0:
print()
computeResult()