This routing mechanism supports (among other things) optional and mandatory parameters, default values, nested routes, and callback functions.

这个路由机制支持可选和必选参数、默认值、嵌套路由以及回调函数。

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Optional packages add even further to the huge collection of standard packages and functions.

可选的程序包为近乎无限的标准程序包和函数集合提供了更进一步的补充。

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Again, these are categorized into the mandatory (functions that are always present in this business pattern) and the optional (functions that may or may not be present).

同样，这些功能也分为必需的功能(在这个业务模式中必须存在的功能)和可选的功能(可有可无的功能)两类。

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Simply connect the camera to an HDTV with an optional HDMI cable and use your HDTV's remote to control playback functions and navigate the camera's menus from the comfort of your couch.

ENGADGET: Olympus unveils a cavalcade of point and shoot cameras and a PEN lens at CES