简要了解了case类和模式匹配之后，接下来让我们回到创建计算器ast的任务上。

Armed with that admittedly brief rundown of case classes and pattern matching, let's return to the task of creating the calculator AST.

youdao

如果您的操作系统是Mac OS X，那么您很可能使用过仪表板widget(计算器、天气、Apple iPod控制器)来完成某些特定的任务。

If you're using Mac OS X, you've probably used a dashboard widget (calculator, weather, Apple iPod controller) to complete some kind of specialized task.

youdao

你有一个自动运行杀手，任务管理器，计算器和文件浏览器，只有让你运行的文件，被列入甚至没有基本的上下文菜单。

You have an Autorun Killer, Task Manager, Calculator and file Explorer that only lets you run files, not even a basic context menu being included.

youdao