swiftlang/swift

[SR-6691] Sequence.split should have a Lazy equivalent

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#49,240 opened on Jan 3, 2018

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 (9 comments) (0 reactions) (1 assignee)Swift (69,989 stars) (10,719 forks)batch import
featuregood first issuestandard libraryswift evolution proposal needed

Description
Previous ID SR-6691
Radar None
Original Reporter @airspeedswift
Type New Feature
Status In Progress
Resolution
Votes 4
Component/s Standard Library
Labels New Feature, StarterBug, StarterProposal
Assignee None
Priority Medium

md5: 1e8d36124b9916625ca75e3f19b449dc

Issue Description:

Sequence.split is eager, but if you are splitting a collection, it should be possible to do it lazily. This could be done via an extension to LazyCollectionProtocol so you could write "a.b.c".lazy.split(separator: ".").

Contributor guide

Tech stack
swift
Domain
api
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
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.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Swift basicsunderstanding of lazy sequencesfamiliarity with Sequence protocol
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
80
Research direction
Start by examining the existing eager split method in Sequence.swift within the Swift standard library. Then locate the LazyCollectionProtocol definition to understand how lazy wrappers are structured. Implement a lazy split extension on LazyCollectionProtocol that returns a lazy sequence of subsequences. Review similar lazy implementations (e.g., lazy filter, lazy map) for pattern reference. Ensure the implementation meets performance expectations for lazy evaluation.