What is the approach to indicating a leaf node in a Swift recursive protocol?

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There are a few ways to indicate a leaf node in a Swift recursive protocol. One approach is to add a Boolean property to the protocol that indicates whether the current node is a leaf. For example:

protocol Tree {
    var isLeaf: Bool { get }
    // other properties and methods
}

Another approach is to define a separate protocol for leaf nodes and have the main protocol inherit from it. For example:

protocol LeafNode {}
protocol TreeNode {
    var children: [TreeNode] { get }
}
struct Leaf: LeafNode {
    // properties and methods for leaf nodes
}
struct InnerNode: TreeNode {
    var children: [TreeNode]
    // properties and methods for inner nodes
}

In this case, any node that conforms to LeafNode is automatically considered a leaf node, while any node that conforms to TreeNode is assumed to have children and therefore not a leaf node.