def parse_str():
'''
解析字符串
'''
if get_next_token().type == 'STR':
rnode = TreeNode('STR')
rnode.line = tokens[tokens_index].pos[0]
rnode.value = get_next_token().name
skip_next_token()
return rnode
else:
raise ParseException('Line %d: token should be a string ' %
get_next_token().pos[0])
def parse_id():
'''
解析标识符
'''
id_token = get_next_token()
if id_token.type != 'ID':
raise ParseException('Line %d: token should be a identifier' %
id_token.pos[0])
skip_next_token()
rnode = TreeNode('ID')
rnode.line = tokens[tokens_index].pos[0]
rnode.value = id_token.name
return rnode
def parse_factor():
'''
解析项中单个因子
'''
node = TreeNode('FACTOR')
node.line = tokens[tokens_index].pos[0]
token = get_next_token()
if token.type == 'NUM':
rnode = TreeNode('NUM')
rnode.line = tokens[tokens_index].pos[0]
rnode.value = token.name
node.add_child(rnode)
skip_next_token()
elif token.name == '(':
check_next_token('(')
node.add_child(parse_expr())
check_next_token(')')
else:
node.add_child(parse_var())
return node
def parse_decl_stmt():
'''
解析声明语句
'''
type_token = get_next_token()
decl_node = TreeNode('VARDECL')
type_node = TreeNode('TYPE')
decl_node.line = tokens[tokens_index].pos[0]
type_node.line = tokens[tokens_index].pos[0]
decl_node.add_child(type_node)
type_node.add_child(check_next_token(type_token.name))
next_token = get_next_token()
if next_token.name == '[': #判断声明是否为数组
check_next_token('[')
num_token = get_next_token()
if num_token.type != 'NUM' or '.' in num_token.name: #声明数组长度时需为正整数
raise ParseException(
'Line %d: length of array should be a positive constant number'
% num_token.pos[0])
num_node = TreeNode('NUM')
num_node.line = tokens[tokens_index].pos[0]
num_node.value = num_token.name
type_node.add_child(num_node)
skip_next_token()
check_next_token(']')
id = parse_id()
decl_node.add_child(id)
next_name = get_next_token().name
assfunc = parse_str if type_token.name == 'string' else parse_expr
while next_name in [',', '=']:
if next_name == '=':
check_next_token('=')
id.add_child(assfunc())
else:
check_next_token(',')
id = parse_id()
decl_node.add_child(id)
next_name = get_next_token().name
check_next_token(';')
return decl_node