标准 ML 二叉树
我仍然遇到这个问题，所以我可以寻求更多帮助。
我们得到：
datatype which = STRING of string | INT of int
第 1 部分。我们被告知需要为包含“which”类型值的二叉树创建另一个名为 whichTree 的数据类型，其中数据仅位于树的叶子处。
我认为这将是正确的答案：
datatype whichTree = Empty | Leaf of which | Node of whichTree*whichTree;
事实证明，这与我运行时不同：
val inttree = Node(Leaf(1), Leaf(2));
我收到错误。
我能够弄清楚我可以做这样的事情：
datatype 'a whichTree = Empty | Leaf of 'a | Node of 'a whichTree * 'a whichTree;
或者
datatype whichTree = Empty | Leaf of int | Node of whichTree*whichTree;
但是这些对我来说似乎都不正确，因为在我的第一种情况下，我的数据类型名称中有一个 'a ，而在我的另一个情况下，当我说 Leaf of int 时应该能够使用 which 来指定 string 或 int。
谁能告诉我正确的答案是什么或为我提供一些帮助？
I am still having problems with this so I can going to ask for more help.
We are given:
datatype which = STRING of string | INT of int
Part 1. We are told we need to created another datatype named whichTree for a binary tree containing the values of type "which" where data is only at the leaves of the tree.
I assumed this would be the correct answer:
datatype whichTree = Empty | Leaf of which | Node of whichTree*whichTree;
It turns out it is not as when I run:
val inttree = Node(Leaf(1), Leaf(2));
I get an error.
I was able to figure out that I can do something like this:
datatype 'a whichTree = Empty | Leaf of 'a | Node of 'a whichTree * 'a whichTree;
or
datatype whichTree = Empty | Leaf of int | Node of whichTree*whichTree;
But neither of these seem correct to me as in my first case my datatype name has a 'a in it and in my other one I am saying Leaf of int when I should be able to specify string or int by using which.
Can anyone tell me what the correct answer it or provide me with some help?
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您对
whichTree的定义是正确的，您只是缺少inttree中which的构造函数：Your definition of
whichTreeis correct, you're just missing the constructor forwhichin yourinttree: