它定义了一种xml语言，可用于定义新类型的词汇表示的正则表达式。
It defines an XML language for defining regular expressions for the lexical representation of new types.
您可以添加消息树的新数据类型或元素，以便在表达式中使用。
You have the ability to add new data types or elements of the message tree for use in the expression.
新的auto语法：根据初始化器(initializer)表达式推导类型。
Welcome to the new auto syntax: type deduction from initializer expressions.
如果相同中介流处理多种消息类型，您可以使用此新原语定义XPath表达式，以将消息指引到不同的终端。
If multiple message types are processed by the same mediation flow, you can use this new primitive to define XPath expressions to direct messages out different terminals.
这次我还是要创建一个新的filter类型，向正则表达式传递一个名为rfilter的闭包，并执行一些assert，以确保每件事都正常。
Again, I'll create a new filter type, pass in the regular expression closure named rfilter and execute some asserts to ensure that everything is peachy. All of this is shown in Listing 3.
可以手工转换或者(最好)编写新的使用这些类型的表达式。
Manually cast them or (better yet) write new expressions that use the typed value for real.
你也希望根据那些特性打开新的推断特性的选项，这允许编译器通过估计右值表达式去推测出局部变量的申明类型。
You'll also want to turn on the new Option infer feature. This allows the compiler to infer local variable type declarations by evaluating the right-hand side of the expression.
由于正则表达式是从文本文件中装载的一个字符串，所以当添加对新类型的邮政编码的支持时，不需要更改代码。
The regular expression is a string loaded from a text file, so you don't need to change the code when you want to add support for a new type of postal code.
若要避免创建新的命名类型所需的额外代码和开销，可以使用对象表达式。
You use object expressions when you want to avoid the extra code and overhead that is required to create a new, named type.
若要避免创建新的命名类型所需的额外代码和开销，可以使用对象表达式。
You use object expressions when you want to avoid the extra code and overhead that is required to create a new, named type.
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