本文翻译自：http://www.dofactory.com/Patterns/PatternInterpreter.aspx
Define:Given a language, define a representation for its grammar along with an interpreter that uses the representation to interpret sentences in the language.
一、解释者模式概念
针对某一编程语言，为其语法定义一定的描述语言和解释器，解释器利用描述语言去解释该编程语言中的所有语法。
二、UML类图
三、参与者
该模式的类/对象参与者包括：
- AbstractExpression (描述)
- 为执行operation()声明一个接口
- TerminalExpression ( ThousandExpression, HundredExpression, TenExpression, OneExpression )
- 在语法中使用终止符实现一个operation解释器
- 在语句中要求所有终止符需要一个实例
- NonterminalExpression ( 不使用 )
- one such class is required for every rule R ::= R1R2...Rn in the grammar
- maintains instance variables of type AbstractExpression for each of the symbols R1 through Rn.
- implements an Interpret operation for nonterminal symbols in the grammar. Interpret typically calls itself recursively on the variables representing R1 through Rn.
- Context (Context)
- 所有全局解释器的内容信息
- Client (InterpreterApp)
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- builds (or is given) an abstract syntax tree representing a particular sent