swift - 为什么我的二元运算符不能应用于正确键入的操作数？

Question

标签： swiftgenericsbinary-search-treeassociated-types

Answer 1

您需要确保K和R.Key属于同一类型，因为您定义了自定义运算符以接受两个相同类型的输入参数。

extension Tree where K == R.Key {
    public func contains(_ key: K) -> Bool {
        switch self {
        case .empty:
            return false
        case let .node(record, left, right):
            switch key ⊰ record.key {
            case .matching: return true
            case .leftTree: return left.contains(key)
            case .rightTree: return right.contains(key)
            }
        }
    }
}

或者您可以修改Tree自身以确保K和R.Key始终是同一类型。

public enum Tree<R: RecordProtocol, K> where R.Key == K {
    case empty
    indirect case node(_ record: R,_ left: Tree<R,K>,_ right: Tree<R,K>)
    public init() {
        self = .empty
    }
}

extension Tree {
    public func contains(_ key: K) -> Bool {
        switch self {
        case .empty:
            return false
        case let .node(record, left, right):
            switch key ⊰ record.key {
            case .matching: return true
            case .leftTree: return left.contains(key)
            case .rightTree: return right.contains(key)
            }
        }
    }
}