class Parser:
def __init__(self):
self.lex = None
def S(self):
if self.lex.cur_token[0] == 'sign':
sign = self.lex.cur_token[1]
self.lex.next_token()
left_tree = self.S()
right_tree = self.SPrime()
return ParsedTree('S', ParsedTree(sign), left_tree, right_tree)
elif self.lex.cur_token[0] == 'number':
number = self.lex.cur_token[1]
self.lex.next_token()
return ParsedTree('S', ParsedTree(number))
# elif self.lex.cur_token[0] == 'end':
# return ParsedTree('S') # !!!
else:
raise BadTokenException(str(self.lex.cur_token))
def SPrime(self):
if self.lex.cur_token[0] in ['sign', 'number']:
sub_tree = self.S()
return ParsedTree("S'", sub_tree)
else:
raise BadTokenException(str(self.lex.cur_token))
def parse(self, stream):
self.lex = LexicalAnalyzer(stream)
self.lex.next_token()
return self.S()
def parse(self, stream):
self.lex = LexicalAnalyzer(stream)
self.lex.next_token()
return self.S()
