帮助声明可变数目的参数 [英] Help In Declaring Variable Number Of Arguments

问题描述

高手们，

我必须为可以有多个节点的树定义多态数据类型。每个节点可以有任意数量的子节点和一个vlaue。这种类型将始终至少有一个节点。我是Haskell的新手，所以我问如何声明节点具有可变数量的参数。

这是我现在拥有的。这是一棵树，可以有一个节点或一个节点值为（a）和两个树孩子。我希望他们成为任何数量的树孩子，而不是两个树孩子。 （Analoog as java可变参数数量arg ...）

 数据树a =节点a |节点a（Tree a）（Tree a）派生（显示）
  

感谢您的帮助

编辑

有点问题:::我怎样才能用变量声明这个节点在函数
参数（头/签名）中。我必须实现一个称为

contains的函数，它将检查Node是否包含特定元素。

 包含:: Tree a  - > b  - > Bool 
包含（Node val [（tree）]）= ...... 
  

第二行是否正确？

解决方案

 数据树a =节点a |节点a [（Tree a）]派生（Show）
  

但是另外还有一个问题，这应该是

 数据树a = Leaf a | Branch a [（Tree a）]派生（Show）
  

或者联合的部分必须有不同的名称，否则你不能使用模式匹配。

Leaf 和分支是数据构造函数，所以：

 分支1 [分支3，分支6 [分支5]] 
  

是树的示例

---

  contains :: Tree a  - > a  - >布尔
包含（Leaf a）b = a == b 
包含（Branch a c）b = a == b ||任何（地图（\ t  - >包含tb）c）
  

或其他

High Guys,

I have to define a polymorphic datatype for a tree that can have multiple nodes. Each node can have any number of children and a vlaue. This type will always have at least one node. I am new in Haskell so am asking how can i declare the node to have variable number of arguments.

This is what i have now. This is a tree that can have a Node or a node with value (a) and two tree children. Instead of two tree children, i want them to be any number of tree children. (Analoog as java variable number of arguments "arg...")

data Tree a = Node a | Node a (Tree a) (Tree a) deriving (Show)

Thanks for your help

EDIT

A little question::: How can i declare this node with variable arguments in a functions parameter(header/signature). I have to implement a function called
"contains" which will check if a Node contains a specific element.

contains :: Tree a -> b -> Bool
contains (Node val [(tree)]) =   ......

Is the second line correct ?

解决方案

it would be:

data Tree a = Node a | Node a [(Tree a)] deriving (Show)

but in addition there is a second problem that this should be

data Tree a = Leaf a | Branch a [(Tree a)] deriving (Show)

or such as the parts of a union must have different names as otherwise you couldn't use pattern matching

Leaf and Branch are data constructors so:

Branch 1 [Leaf 3, Branch 6 [Leaf 5]]

is an example of a Tree

---

contains :: Tree a -> a -> Boolean 
contains (Leaf a) b = a == b
contains (Branch a c) b = a == b || any (map (\t -> contains t b) c)

or such

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