Values for array type components can contain zero or one element, and values for set and tree type components can have zero or more elements.

用于数组类型的组件的值可以包含0个或1个元素，用于集合和树类型的组件的值可以包含0到多个元素。

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In this paper, the design principles and application of tools for machining fir-tree type slot are presented.

介绍了枞树型轮槽铣刀的设计原理及应用。

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Combining with the development of computerized logging software, this paper introduces the storing and accessing of tree type data, and gives the complement in the logging data.

文章结合数控测井软件开发实际，详细介绍了树型数据的存储、访问以及在测井软件中测井数据组织中的应用。

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Davis saw clear cutting in Alabama and man-made forests with only one type of tree.

CNN: Trekking 5,000 miles to connect man and wildlife

The active ingredient is taken from a type of yew tree.

ECONOMIST: The bitter pills | The