swiftlang/swift

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

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#49,413 opened on Jan 29, 2018

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featuregood first issuestandard libraryswift evolution proposal needed

Description
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)}}.

Contributor guide

Tech stack
swift
Domain
apideveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Swift programming basicsSequence protocol familiarity
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
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.
[SR-6864] Add a "cycle" method to the standard library · swiftlang/swift#49413 | Good First Issue