由括号表示分组：括号中包含的任何子表达式都被看作是用于以后分组或循环的原子。
Grouping is indicated by parentheses: any sub-expression contained in parentheses is treated as if it were atomic for the purpose of further grouping or repetition.
由括号表示分组：括号中包含的任何子表达式都被看作是用于以后分组或循环的原子。
Grouping is indicated by parentheses: any sub-expression contained in parentheses is treated as if it were atomic for the purpose of further grouping or repetition.
应用推荐