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# Copyright 2015 Egor Tensin <Egor.Tensin@gmail.com>
# This file is licensed under the terms of the MIT License.
# See LICENSE.txt for details.
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__)
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