swiftlang/swift

[SR-6864] Add a "cycle" method to the standard library

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#49,413 建立於 2018年1月29日

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featuregood first issuestandard libraryswift evolution proposal needed

描述
Previous ID SR-6864
Radar None
Original Reporter @airspeedswift
Type New Feature
Votes 0
Component/s Standard Library
Labels New Feature, StarterProposal
Assignee None
Priority Medium

md5: ce3f8a07c6a7edad8e1997fb1e825980

Issue Description:

It is often useful to cycle over a sequence indefinitely. For example, just like you can write zip(repeatElement("foo", count: Int.max), myArray) and zip(1..., myArray), you could write {{zip([.grey,.white].cycle(), myArray)}}.

貢獻者指南

技術棧
swift
領域
apideveloper experience
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。
2
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。
1-3 hours
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 programming basicsSequence protocol familiarity
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。
80
研究方向
Review the existing Sequence protocol in the Swift standard library (see file: stdlib/public/core/Sequence.swift). Examine how similar methods like repeatElement are implemented. Check if there are any prior proposals or discussions about this feature in the Swift Evolution process. Determine whether the cycle method should produce a lazy sequence or an eager collection. The implementation should respect Sequence semantics and potentially use LazySequenceProtocol.