def 表达式(self):
sub_tree = TreeNode('<表达式>')
child_tree = None
heading_operator = None
syntax_tree = None
if isinstance(self.token, Operator) and self.token.value in ['+', '-']:
# TODO
child_tree = TreeNode(self.token)
heading_operator = self.token.value
self.token = self.lexer.forward()
anal_term, ast_term = self.项()
if child_tree is not None:
child_tree.sublings.append(anal_term)
else:
child_tree = anal_term
if heading_operator is None or heading_operator in ['+']:
syntax_tree = ast_term
else:
ast_heading_zero = TreeNode(Int(0))
syntax_tree = SyntaxTree.BinaryExpression(heading_operator, ast_heading_zero, ast_term)
while isinstance(self.token, Operator) and self.token.value in ['+', '-']:
anal_add, ast_add = self.加法运算符()
child_tree.sublings.append(anal_add)
anal_term, rhs_term = self.项()
syntax_tree = SyntaxTree.BinaryExpression(ast_add, syntax_tree, rhs_term)
child_tree.sublings.append(anal_term)
else:
sub_tree.child = child_tree
return sub_tree, syntax_tree
def 项(self):
sub_tree = TreeNode('<项>')
child_tree, ast_tree = self.因子()
while isinstance(self.token, Operator) and self.token.value in ['*', '/']:
anal_mul, ast_mul = self.乘法运算符()
child_tree.sublings.append(anal_mul)
fractor, ast_fractor = self.因子()
ast_tree = SyntaxTree.BinaryExpression(ast_mul, ast_tree, ast_fractor)
child_tree.sublings.append(fractor)
else:
sub_tree.child = child_tree
return sub_tree, ast_tree
def 条件(self):
sub_tree = TreeNode('<条件>')
syntax_tree = None
if isinstance(self.token, Keyword) and self.token.value == 'odd':
child_tree = TreeNode(self.token)
self.token = self.lexer.forward()
expression, ast_expression = self.表达式()
syntax_tree = SyntaxTree.OddStatement(ast_expression)
else:
expression, ast_lhs = self.表达式()
child_tree = expression
operator, ast_operator = self.关系运算符()
child_tree.sublings.append(operator)
expression, ast_rhs = self.表达式()
syntax_tree = SyntaxTree.BinaryExpression(ast_operator, ast_lhs, ast_rhs)
child_tree.sublings.append(expression)
sub_tree.child = child_tree
return sub_tree, syntax_tree