swiftlang/swift

[SR-3419] Strides should be collections

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#46,007 建立於 2016年12月14日

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affects ABIgood first issueimprovementstandard libraryswift evolution proposal needed

描述
Previous ID SR-3419
Radar rdar://problem/17816925
Original Reporter @airspeedswift
Type Improvement
Votes 0
Component/s Standard Library
Labels Improvement, AffectsABI, StarterProposal, swift-evolution-proposal-needed
Assignee None
Priority Medium

md5: 20684cd6a789b38a9426158bdf2d0b60

Issue Description:

In Swift 3.0, StrideTo and StrideThrough conform to Sequence, but not Collection.

While they can't be bi-directional or random-access, as the last (or abitrary) element can't necessarily be reached in O( n ) for all strideable types, it should be possible to make them forward-only collections. One straightforward implementation would be to make the index each value zipped with a count (for Comparable purposes).

Once we have conditional conformance, it should be possible to make specific strides (e.g. ones over integers) conform to random access.

貢獻者指南

技術棧
swift
領域
api
議題類型
feature
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-2 days
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
stale
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
clear
前置要求
Swift protocolsCollection conformanceGenericsSwift standard library
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
70
研究方向
Review the current StrideTo and StrideThrough implementations in the Swift standard library to understand their Sequence conformance. Explore how to add Collection conformance by creating a custom index type that pairs each stride value with a count. Investigate the possibility of conditional conformance for random access strides over integer types.