W3Eval的表达式可以包含三种括号：标准圆括号、方括号和花括号。
Expressions in W3Eval can contain three kind of parentheses: standard parentheses, square brackets, and curly braces.
当然，有时候您不得不在参数周围加上圆括号，或者表达式没有按照您计划的方式求值，但该原则不仅如此。
Sure, there are times when you have to put parentheses around arguments or an expression doesn't evaluate the way you planned, but there's more to this principle than that.
组是正则表达式中的子模式，它们包含在圆括号中。
Groups are subpatterns in the regular expression that are surrounded by parenthesis.
使用(和)圆括号(就像数学中的用法)将修饰符应用到子表达式。
Use (and) parentheses (just as you do in mathematics) to apply a modifier to a subexpression. Here's an example: Given text file test.txt.
要调用函数并使用它的返回值作为语言表达式的一部分，只需要命名它并附加一个使用圆括号括起的参数列表。
To call a function and use its return value as part of a larger expression, simply name it and append a parenthesized argument list.
第一个规则表达式将与后面依次跟有任意数量的空格或制表键以及开始圆括号的字符串“main ”匹配。
The first regular expression will match the string "main" followed by any number of Spaces or tabs, followed by an open parenthesis.
有些时候你需要使用圆括号对子表达式分组，但是却不想这个括号里面的内容再作为标示子表达式，在这种情况下可使用非标示圆括号？
Sometimes you need to group sub-expressions with parenthesis, but don't want the parenthesis to spit out another marked sub-expression, in this case a non-marking parenthesis ?
如果有怀疑，则在表达式上按程序逻辑要求使用圆括号强制操作数的组合。
When in doubt, parenthesize expressions to force the grouping that the logic of your program requires.
如果程序员不想考虑这些规则，可以在复合表达式中使用圆括号强制实现某个特殊的分组。
Programmers can override these rules by parenthesizing compound expressions to force a particular grouping.
作为例子，我们将要写一个计算由浮点数、圆括号及一些常用的加、减等算术符号组成的算术表达式的程序。
As an example we will write a small program to read and evaluate arithmetic expressions consisting of floating point Numbers, parentheses and the usual operators for addition, subtraction, and so on.
例如我们要写一个计算由浮点数、圆括号及一些常用的加、减等算术符号组成的算术表达式的程序。
As an example we will write a small program to read and evaluate arithmetic expressions consisting of floating point Numbers, parentheses and the usual operators for addition, subtraction, and so on.
你们可能会想起小学时，将一些加法表达式，放在圆括号里，这样加法可以先计算，然后是乘法，否则，乘法默认先发生。
You might recall from grade school sometimes you put things in parentheses so that your addition happens first, then your multiplication, otherwise multiplication would happen by default first.
当我们要在一个更大的表达式中嵌入条件表达式时，通常必须用圆括号把条件表达式括起来。
When we embed a conditional expression in a larger expression, we usually must parenthesize the conditional subexpression.
当我们要在一个更大的表达式中嵌入条件表达式时，通常必须用圆括号把条件表达式括起来。
When we embed a conditional expression in a larger expression, we usually must parenthesize the conditional subexpression.
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