-
Notifications
You must be signed in to change notification settings - Fork 420
/
Copy pathspi.py
480 lines (371 loc) · 12.9 KB
/
spi.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
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
""" SPI - Simple Pascal Interpreter. Part 9."""
###############################################################################
# #
# LEXER #
# #
###############################################################################
# Token types
#
# EOF (end-of-file) token is used to indicate that
# there is no more input left for lexical analysis
(INTEGER, PLUS, MINUS, MUL, DIV, LPAREN, RPAREN, ID, ASSIGN,
BEGIN, END, SEMI, DOT, EOF) = (
'INTEGER', 'PLUS', 'MINUS', 'MUL', 'DIV', '(', ')', 'ID', 'ASSIGN',
'BEGIN', 'END', 'SEMI', 'DOT', 'EOF'
)
class Token(object):
def __init__(self, type, value):
self.type = type
self.value = value
def __str__(self):
"""String representation of the class instance.
Examples:
Token(INTEGER, 3)
Token(PLUS, '+')
Token(MUL, '*')
"""
return 'Token({type}, {value})'.format(
type=self.type,
value=repr(self.value)
)
def __repr__(self):
return self.__str__()
RESERVED_KEYWORDS = {
'BEGIN': Token('BEGIN', 'BEGIN'),
'END': Token('END', 'END'),
}
class Lexer(object):
def __init__(self, text):
# client string input, e.g. "4 + 2 * 3 - 6 / 2"
self.text = text
# self.pos is an index into self.text
self.pos = 0
self.current_char = self.text[self.pos]
def error(self):
raise Exception('Invalid character')
def advance(self):
"""Advance the `pos` pointer and set the `current_char` variable."""
self.pos += 1
if self.pos > len(self.text) - 1:
self.current_char = None # Indicates end of input
else:
self.current_char = self.text[self.pos]
def peek(self):
peek_pos = self.pos + 1
if peek_pos > len(self.text) - 1:
return None
else:
return self.text[peek_pos]
def skip_whitespace(self):
while self.current_char is not None and self.current_char.isspace():
self.advance()
def integer(self):
"""Return a (multidigit) integer consumed from the input."""
result = ''
while self.current_char is not None and self.current_char.isdigit():
result += self.current_char
self.advance()
return int(result)
def _id(self):
"""Handle identifiers and reserved keywords"""
result = ''
while self.current_char is not None and self.current_char.isalnum():
result += self.current_char
self.advance()
token = RESERVED_KEYWORDS.get(result, Token(ID, result))
return token
def get_next_token(self):
"""Lexical analyzer (also known as scanner or tokenizer)
This method is responsible for breaking a sentence
apart into tokens. One token at a time.
"""
while self.current_char is not None:
if self.current_char.isspace():
self.skip_whitespace()
continue
if self.current_char.isalpha():
return self._id()
if self.current_char.isdigit():
return Token(INTEGER, self.integer())
if self.current_char == ':' and self.peek() == '=':
self.advance()
self.advance()
return Token(ASSIGN, ':=')
if self.current_char == ';':
self.advance()
return Token(SEMI, ';')
if self.current_char == '+':
self.advance()
return Token(PLUS, '+')
if self.current_char == '-':
self.advance()
return Token(MINUS, '-')
if self.current_char == '*':
self.advance()
return Token(MUL, '*')
if self.current_char == '/':
self.advance()
return Token(DIV, '/')
if self.current_char == '(':
self.advance()
return Token(LPAREN, '(')
if self.current_char == ')':
self.advance()
return Token(RPAREN, ')')
if self.current_char == '.':
self.advance()
return Token(DOT, '.')
self.error()
return Token(EOF, None)
###############################################################################
# #
# PARSER #
# #
###############################################################################
class AST(object):
pass
class BinOp(AST):
def __init__(self, left, op, right):
self.left = left
self.token = self.op = op
self.right = right
class Num(AST):
def __init__(self, token):
self.token = token
self.value = token.value
class UnaryOp(AST):
def __init__(self, op, expr):
self.token = self.op = op
self.expr = expr
class Compound(AST):
"""Represents a 'BEGIN ... END' block"""
def __init__(self):
self.children = []
class Assign(AST):
def __init__(self, left, op, right):
self.left = left
self.token = self.op = op
self.right = right
class Var(AST):
"""The Var node is constructed out of ID token."""
def __init__(self, token):
self.token = token
self.value = token.value
class NoOp(AST):
pass
class Parser(object):
def __init__(self, lexer):
self.lexer = lexer
# set current token to the first token taken from the input
self.current_token = self.lexer.get_next_token()
def error(self):
raise Exception('Invalid syntax')
def eat(self, token_type):
# compare the current token type with the passed token
# type and if they match then "eat" the current token
# and assign the next token to the self.current_token,
# otherwise raise an exception.
if self.current_token.type == token_type:
self.current_token = self.lexer.get_next_token()
else:
self.error()
def program(self):
"""program : compound_statement DOT"""
node = self.compound_statement()
self.eat(DOT)
return node
def compound_statement(self):
"""
compound_statement: BEGIN statement_list END
"""
self.eat(BEGIN)
nodes = self.statement_list()
self.eat(END)
root = Compound()
for node in nodes:
root.children.append(node)
return root
def statement_list(self):
"""
statement_list : statement
| statement SEMI statement_list
"""
node = self.statement()
results = [node]
while self.current_token.type == SEMI:
self.eat(SEMI)
results.append(self.statement())
if self.current_token.type == ID:
self.error()
return results
def statement(self):
"""
statement : compound_statement
| assignment_statement
| empty
"""
if self.current_token.type == BEGIN:
node = self.compound_statement()
elif self.current_token.type == ID:
node = self.assignment_statement()
else:
node = self.empty()
return node
def assignment_statement(self):
"""
assignment_statement : variable ASSIGN expr
"""
left = self.variable()
token = self.current_token
self.eat(ASSIGN)
right = self.expr()
node = Assign(left, token, right)
return node
def variable(self):
"""
variable : ID
"""
node = Var(self.current_token)
self.eat(ID)
return node
def empty(self):
"""An empty production"""
return NoOp()
def expr(self):
"""
expr : term ((PLUS | MINUS) term)*
"""
node = self.term()
while self.current_token.type in (PLUS, MINUS):
token = self.current_token
if token.type == PLUS:
self.eat(PLUS)
elif token.type == MINUS:
self.eat(MINUS)
node = BinOp(left=node, op=token, right=self.term())
return node
def term(self):
"""term : factor ((MUL | DIV) factor)*"""
node = self.factor()
while self.current_token.type in (MUL, DIV):
token = self.current_token
if token.type == MUL:
self.eat(MUL)
elif token.type == DIV:
self.eat(DIV)
node = BinOp(left=node, op=token, right=self.factor())
return node
def factor(self):
"""factor : PLUS factor
| MINUS factor
| INTEGER
| LPAREN expr RPAREN
| variable
"""
token = self.current_token
if token.type == PLUS:
self.eat(PLUS)
node = UnaryOp(token, self.factor())
return node
elif token.type == MINUS:
self.eat(MINUS)
node = UnaryOp(token, self.factor())
return node
elif token.type == INTEGER:
self.eat(INTEGER)
return Num(token)
elif token.type == LPAREN:
self.eat(LPAREN)
node = self.expr()
self.eat(RPAREN)
return node
else:
node = self.variable()
return node
def parse(self):
"""
program : compound_statement DOT
compound_statement : BEGIN statement_list END
statement_list : statement
| statement SEMI statement_list
statement : compound_statement
| assignment_statement
| empty
assignment_statement : variable ASSIGN expr
empty :
expr: term ((PLUS | MINUS) term)*
term: factor ((MUL | DIV) factor)*
factor : PLUS factor
| MINUS factor
| INTEGER
| LPAREN expr RPAREN
| variable
variable: ID
"""
node = self.program()
if self.current_token.type != EOF:
self.error()
return node
###############################################################################
# #
# INTERPRETER #
# #
###############################################################################
class NodeVisitor(object):
def visit(self, node):
method_name = 'visit_' + type(node).__name__
visitor = getattr(self, method_name, self.generic_visit)
return visitor(node)
def generic_visit(self, node):
raise Exception('No visit_{} method'.format(type(node).__name__))
class Interpreter(NodeVisitor):
GLOBAL_SCOPE = {}
def __init__(self, parser):
self.parser = parser
def visit_BinOp(self, node):
if node.op.type == PLUS:
return self.visit(node.left) + self.visit(node.right)
elif node.op.type == MINUS:
return self.visit(node.left) - self.visit(node.right)
elif node.op.type == MUL:
return self.visit(node.left) * self.visit(node.right)
elif node.op.type == DIV:
return self.visit(node.left) // self.visit(node.right)
def visit_Num(self, node):
return node.value
def visit_UnaryOp(self, node):
op = node.op.type
if op == PLUS:
return +self.visit(node.expr)
elif op == MINUS:
return -self.visit(node.expr)
def visit_Compound(self, node):
for child in node.children:
self.visit(child)
def visit_Assign(self, node):
var_name = node.left.value
self.GLOBAL_SCOPE[var_name] = self.visit(node.right)
def visit_Var(self, node):
var_name = node.value
val = self.GLOBAL_SCOPE.get(var_name)
if val is None:
raise NameError(repr(var_name))
else:
return val
def visit_NoOp(self, node):
pass
def interpret(self):
tree = self.parser.parse()
if tree is None:
return ''
return self.visit(tree)
def main():
import sys
text = open(sys.argv[1], 'r').read()
lexer = Lexer(text)
parser = Parser(lexer)
interpreter = Interpreter(parser)
result = interpreter.interpret()
print(interpreter.GLOBAL_SCOPE)
if __name__ == '__main__':
main()