def __init__(self, path):
self.path = path
self.file = open(path, 'r')
self.code = self.file.read() + '$$'
self.file.close()
self.lexer = Lex.Lexer(self.code)
self.operands = Stack()
self.operators = Stack()
self.operators.push(Lex.Token('sentinel', 'sentinel'))
def parse_factor(self):
pos_0 = self.lexer.pos
tok = self.lexer.scan()
if tok.token == "INT":
self.operands.push(int(tok.att))
return 1
if tok.token == "ID":
return 1
if tok.att == "(":
self.operators.push(Lex.Token('sentinel', 'sentinel'))
if self.parse_expr():
tok = self.lexer.scan()
if tok.att == ")":
self.operators.pop()
return 1
#reset position in text file on failure
self.lexer.pos = pos_0
return 0
def Unit(self, priority):
if priority == 0:
if self.current_token.type == LPAREN:
self.eat(LPAREN)
ans = self.Unit(Max_Priority)
self.eat(RPAREN)
elif self.current_token.type == NUM:
ans = AST_Num(self.current_token.value)
self.eat(NUM)
elif self.current_token.type == STRING:
ans = AST_String(self.current_token.value)
self.eat(STRING)
elif self.current_token.type in UnaryOp:
token = self.current_token
self.eat(token.type)
ans = AST_UnaryOp(token, self.Unit(0))
elif self.current_token.type == NAME:
name = self.current_token.value
self.eat(NAME)
if self.current_token.type == LPAREN:
self.eat(LPAREN)
arglist = []
if self.current_token.type != RPAREN:
arglist.append(self.Unit(Max_Priority))
while self.current_token.type != RPAREN:
self.eat(COMMA)
arglist.append(self.Unit(Max_Priority))
self.eat(RPAREN)
ans = AST_FuncCall(name, arglist)
else:
ans = AST_ID(name)
elif self.current_token.type == LBRACK:
self.eat(LBRACK)
lst = []
if self.current_token.type != RBRACK:
lst.append(self.Unit(Max_Priority))
while self.current_token.type == COMMA:
self.eat(COMMA)
lst.append(self.Unit(Max_Priority))
self.eat(RBRACK)
ans = AST_Array(lst)
else:
self.Error('invalid syntax at "%r" at pos %d' %
(self.lexer.get_local_text(), self.lexer.pos - 1l))
while self.current_token.type == LBRACK:
self.eat(LBRACK)
ind = self.Unit(Max_Priority)
self.eat(RBRACK)
ans = AST_BinOp(Lexer.Token(INDEX, '[]'), ans, ind)
elif Associativity[priority] == LeftAssoc:
ans = self.Unit(priority - 1)
while self.current_token.type in Prio and Prio[
self.current_token.type] == priority:
token = self.current_token
self.eat(token.type)
ans = AST_BinOp(token, ans, self.Unit(priority - 1))
else:
ans = self.Unit(priority - 1)
rightest_node = ans
first = True
while self.current_token.type in Prio and Prio[
self.current_token.type] == priority:
token = self.current_token
self.eat(token.type)
if first:
ans = AST_BinOp(token, ans, self.Unit(priority - 1))
rightest_node = ans
first = False
else:
rightest_node.rson = AST_BinOp(token, rightest_node.rson,
self.Unit(priority - 1))
rightest_node = rightest_node.rson
return ans
