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
|
# Copyright (c) 2015 Egor Tensin <Egor.Tensin@gmail.com>
# This file is part of the "Simple interpreter" project.
# For details, see https://github.com/egor-tensin/simple-interpreter.
# Distributed under the MIT License.
import re
from tokens import *
class LexerError(RuntimeError):
pass
class Lexer:
def __init__(self, src_file):
self._line_buf = ''
self._tok_buf = []
self._src_file = src_file
self._ws_re = re.compile(r'^\s+')
self._identifier_re = re.compile(r'^[^\W\d]\w*')
self._const_toks = {
'+': AdditionOpToken,
'-': SubtractionOpToken,
'*': MultiplicationOpToken,
'/': DivisionOpToken,
':=': AssignmentOpToken,
';': SemicolonToken,
'(': OpeningParenToken,
')': ClosingParenToken,
'{': OpeningBraceToken,
'}': ClosingBraceToken,
'&&': AndOpToken,
'||': OrOpToken,
'==': EqualsOpToken,
'!=': NotEqualsOpToken,
}
self._const_toks_sorted = list(self._const_toks.keys())
self._const_toks_sorted.sort()
self._make_sure_const_tokens_dont_match_identifier_re()
self._keywords = {
'if': IfToken,
'print': PrintToken,
'True': TrueToken,
'False': FalseToken,
}
self._make_sure_keywords_match_identifier_re()
def _make_sure_keywords_match_identifier_re(self):
for kw in self._keywords:
if not re.match(self._identifier_re, kw):
raise LexerError("keyword '%s' is not an identifier" % (kw))
def _make_sure_const_tokens_dont_match_identifier_re(self):
for t in self._const_toks_sorted:
if re.match(self._identifier_re, t):
raise LexerError("const token '%s' is an identifier" % (t))
def _try_require_line_buf(self):
if self._line_buf:
return True
if self._src_file is None:
return False
self._line_buf = self._src_file.readline()
if not self._line_buf:
self._src_file = None
return False
return True
def _eat_number_after_e_sign(self, acc):
m_after_e_sign = re.match(r'^[\-+]?\d+', self._line_buf)
if m_after_e_sign:
after_e_sign = m_after_e_sign.group(0)
self._line_buf = self._line_buf[len(after_e_sign):]
return FloatingPointNumberToken('%s%s' % (acc, after_e_sign))
raise LexerError("'%c' unexpected" % (self._line_buf[0]))
def _eat_number_after_dec_mark(self, acc):
if not self._line_buf:
return FloatingPointNumberToken(acc)
m_digits = re.match(r'^\d+', self._line_buf)
if m_digits:
digits = m_digits.group(0)
self._line_buf = self._line_buf[len(digits):]
return self._eat_number_after_dec_mark('%s%s' % (acc, digits))
m_e_sign = re.match(r'^[eE]', self._line_buf)
if m_e_sign:
e_sign = m_e_sign.group(0)
self._line_buf = self._line_buf[len(e_sign):]
return self._eat_number_after_e_sign('%s%s' % (acc, e_sign))
return FloatingPointNumberToken(acc)
def _eat_number_after_first_digit(self, acc):
if not self._line_buf:
return IntegerNumberToken(acc)
m_digits = re.match(r'^\d+', self._line_buf)
if m_digits:
digits = m_digits.group(0)
self._line_buf = self._line_buf[len(digits):]
return self._eat_number_after_first_digit('%s%s' % (acc, digits))
m_e_sign = re.match(r'^[eE]', self._line_buf)
if m_e_sign:
e_sign = m_e_sign.group(0)
self._line_buf = self._line_buf[len(e_sign):]
return self._eat_number_after_e_sign('%s%s' % (acc, e_sign))
m_dec_mark = re.match(r'^\.', self._line_buf)
if m_dec_mark:
dec_mark = m_dec_mark.group(0)
self._line_buf = self._line_buf[len(dec_mark):]
return self._eat_number_after_dec_mark('%s%s' % (acc, dec_mark))
return IntegerNumberToken(acc)
def _try_eat_number(self):
m_first_digit = re.match(r'^\d', self._line_buf)
if m_first_digit:
first_digit = m_first_digit.group(0)
self._line_buf = self._line_buf[len(first_digit):]
return self._eat_number_after_first_digit(first_digit)
m_dec_mark = re.match(r'^\.\d', self._line_buf)
if m_dec_mark:
dec_mark = m_dec_mark.group(0)
self._line_buf = self._line_buf[len(dec_mark):]
return self._eat_number_after_dec_mark(dec_mark)
return False
def _try_eat_ws(self):
while True:
if not self._try_require_line_buf():
return False
m_ws = re.match(self._ws_re, self._line_buf)
if not m_ws:
return True
self._line_buf = self._line_buf[len(m_ws.group(0)):]
return True
def _try_eat_identifier_or_keyword(self):
m_identifier = re.match(self._identifier_re, self._line_buf)
if m_identifier:
identifier = m_identifier.group(0)
self._line_buf = self._line_buf[len(identifier):]
if identifier in self._keywords:
return self._keywords[identifier]()
else:
return IdentifierToken(identifier)
return False
def _try_eat_const_token(self):
for t in self._const_toks_sorted:
if self._line_buf.startswith(t):
self._line_buf = self._line_buf[len(t):]
return self._const_toks[t]()
return False
def _try_eat_token(self):
if not self._try_eat_ws():
return False
const_tok = self._try_eat_const_token()
if const_tok:
self._tok_buf.append(const_tok)
return const_tok
identifier_or_keyword = self._try_eat_identifier_or_keyword()
if identifier_or_keyword:
self._tok_buf.append(identifier_or_keyword)
return identifier_or_keyword
number = self._try_eat_number()
if number:
self._tok_buf.append(number)
return number
raise LexerError("'%c' unexpected" % (self._line_buf[0]))
def _try_require_tok_buf(self, n = 1):
if n < 1:
raise LexerError("unable to require %d tokens" % (n))
while len(self._tok_buf) < n:
if not self._try_eat_token():
return False
return True
def has_next_token(self, n = 1):
return self._try_require_tok_buf(n)
def preview_next_token(self, n = 0):
if not self.has_next_token(n + 1):
raise LexerError("not enough tokens")
return self._tok_buf[n]
def drop_next_token(self, n = 1):
if not self.has_next_token(n):
raise LexerError("not enough tokens")
if n == 1:
return self._tok_buf.pop(0)
else:
xs = self._tok_buf[:n]
self._tok_buf = self._tok_buf[n:]
return xs
if __name__ == '__main__':
import argparse
parser = argparse.ArgumentParser()
parser.add_argument('src_path', help='set soure file path')
args = parser.parse_args()
with open(args.src_path, 'r') as src_file:
lexer = Lexer(src_file)
while lexer.has_next_token():
print(lexer.drop_next_token().__class__.__name__)
|
