swift – Stridable Protocol

发布时间：2020-12-14 05:33:12 所属栏目：百科来源：网络整理

导读：我试图转换以下 Swift 2.3代码： //Example usage://(0 .. 778).binarySearch { $0 145 } // 145extension CollectionType where Index: RandomAccessIndexType { /// Finds such index N that predicate is true for all elements up to /// but not includ

我试图转换以下 Swift 2.3代码：

//Example usage:
//(0 ..< 778).binarySearch { $0 < 145 } // 145
extension CollectionType where Index: RandomAccessIndexType {

    /// Finds such index N that predicate is true for all elements up to
    /// but not including the index N,and is false for all elements
    /// starting with index N.
    /// Behavior is undefined if there is no such N.
    func binarySearch(predicate: Generator.Element -> Bool)
        -> Index {
        var low = startIndex
        var high = endIndex
        while low != high {
            let mid = low.advancedBy(low.distanceTo(high) / 2)
            if predicate(self[mid]) {
                low = mid.advancedBy(1)
            } else {
                high = mid
            }
        }
        return low
    }
}

进入Swift 3如下：

//Example usage:
//(0 ..< 778).binarySearch { $0 < 145 } // 145
extension Collection where Index: Strideable {

    /// Finds such index N that predicate is true for all elements up to
    /// but not including the index N,and is false for all elements
    /// starting with index N.
    /// Behavior is undefined if there is no such N.
    func binarySearch(predicate: (Generator.Element) -> Bool)
        -> Index {
        var low = startIndex
        var high = endIndex
        while low != high {
            let mid = low.advanced(by: low.distance(to: high) / 2)
            if predicate(self[mid]) {
                low = mid.advanced(to: 1)
            } else {
                high = mid
            }
        }
        return low
    }
}

错误

Binary operator ‘/’ cannot be applied to operands of type ‘self.Index.Stride’ and ‘Int’

抛出让mid = low.advanced(by：low.distance(to：high)/ 2)

有关如何修复它的任何帮助？

在Swift 3中,“集合移动他们的索引”,比较
关于Swift进化的 A New Model for Collections and Indices.特别是,您不要在索引上调用advancedBy(),
但是在集合上使用index()方法来推进索引.

所以你的方法将在Swift 3中实现

extension Collection {

    func binarySearch(predicate: (Iterator.Element) -> Bool) -> Index {
        var low = startIndex
        var high = endIndex
        while low != high {
            let mid = index(low,offsetBy: distance(from: low,to: high)/2)
            if predicate(self[mid]) {
                low = index(after: mid)
            } else {
                high = mid
            }
        }
        return low
    }
}

不需要对索引类型进行任何限制.

（编辑：李大同）

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