Parts of the above syntax shown in square brackets can be left out (in which case you have to leave the brackets out too).
以上在方括号中显示的语法部分可以省去（在此情况下，必须将括号也省去）。used to indicate aggregation OR to clarify the grouping of quantities when parentheses and square brackets have already been used.
一对大括号，当圆括号和方括号已经用过时用于表示加总或标出一个数量组When the result of the call must be used inside some expression, you need to add brackets around the call, like shown on the second line.
当调用的结果要在某个表达式中使用时，你必须用方括号把调用括起来，就象前面第二行语句那样。However, within square brackets the current node is usually different from the context node.
当然，在方括号内当前节点一般和上下文节点就不同了。The open and close brackets ([ and ]) mark the beginning and end of the code block, respectively.
开方括号和闭方括号（[和]）分别标志代码块的开始和结束。Square brackets around a field indicate that the field was not used for segmentation.
围绕一个字段的方括号说明该字段不适用于细分。"The text that is currently on the table contains 200 pages with a feast of alternatives and a forest of square brackets, " he said.
眼下提交讨论的文件有二百页之多，其中有琳琅满目的备选方案，还有无数的方括号。It can be easy to forget to qualify names or include square brackets, and thus introduce errors into your code and make it harder to read.
人们很容易忘记对名称进行限制或加方括号，因而导致代码错误并使其难以阅读。Within the brackets, you can refer to a range of characters by using - (hyphen), as in [a-z] or all lowercase letters.
在方括号中，通过使用-（连字符），比如[a-z]或者所有的小写字母，您可以引用某个范围的字符。