When considering a tree of nodes where each node is an immutable data structure, we must consider how to modify a node or nodes inside the tree without modifying the entire tree.

在考虑每个节点都是一个不可变数据结构的节点树时，我们必须考虑如何修改树内的一个节点或多个节点，而不必更改整个树。

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Figure 4 shows an example: consider the case when you right-click the node of the tree.

图4显示了一个范例：当您右击树形结构的节点时，考虑一下这个例子。

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Before we consider the question of tree manipulation, let's consider the data structure we'll use to define each node of the tree.

在考虑树操作问题之前，让我们来看看将用于定义树的各个节点的数据结构。

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The point I wanted to make is that for every node, except the leaves, the leaves are the bottom of a tree in this case, are weird, right, they draw trees where the root is at the top, and the leaves are at the bottom.

你没必要看到整棵树，我想说的重点是,对每个节点来说，除了叶子节点,叶子节点指的是树的最下面的节点，电脑科学家都很奇怪,他们画树的时候根是在最上面的。

麻省理工公开课 - 计算机科学及编程导论课程节选