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apple/swift-collections

Swift package providing commonly used data structures such as deques, heaps, ordered sets and dictionaries, and bit sets for Swift developers.

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What is it?

Swift Collections is a Swift package of data structure implementations that extend the standard library's Array, Set, and Dictionary types. It is organized into thematic modules, including DequeModule for double-ended queues backed by a ring buffer, HeapModule for a min-max heap usable as a priority queue, and OrderedCollections for OrderedSet and OrderedDictionary, which preserve insertion order.

Other modules cover BitCollections (BitSet and BitArray for more compact bit-based storage), HashTreeCollections (persistent hashed TreeSet and TreeDictionary built on CHAMP tries that share unchanged parts across copies), and BasicContainers (ownership-aware UniqueArray and RigidArray). The Collections module re-exports the main stable types through a single import.

The package follows semantic versioning and requires a recent Swift toolchain, with the minimum version listed per release. Experimental features such as SortedCollections, Robin Hood hashed containers, and container protocol previews are gated behind opt-in package traits and are not stable API.

Key features

  • 01Deque, heap, OrderedSet and OrderedDictionary types for common collection needs.
  • 02BitSet and BitArray for compact bit-based storage.
  • 03Persistent TreeSet and TreeDictionary that share unchanged parts across copies.
  • 04Single Collections import exposes the main stable types.
  • 05Semantic versioning with a documented minimum Swift toolchain per release.

Use cases

  • Maintaining insertion order in a Swift dictionary or set without writing custom code.
  • Using a priority queue or double-ended queue in a Swift server or app.
  • Storing large sets of integers or booleans more compactly with bit-based types.
  • Sharing immutable snapshots of a dictionary across threads or states with persistent trees.

Quick start

  1. 1

    Add swift-collections as a package dependency in your Package.swift, as described in the README's usage section

Things to know

  • Experimental features behind package traits are unstable and may change or be removed without notice.
  • Requires a Swift toolchain, so it is only useful for Swift projects.

Topics

#data-structures#collections#queue#heap#ordered-dictionary#bitset#hashing#collection#container#deque

FAQ

What is swift-collections?
Swift package providing commonly used data structures such as deques, heaps, ordered sets and dictionaries, and bit sets for Swift developers. Swift Collections is a Swift package of data structure implementations that extend the standard library's Array, Set, and Dictionary types. It is organized into thematic modules, including DequeModule for double-ended queues backed by a ring buffer, HeapModule for a min-max heap usable as a priority queue, and OrderedCollections for OrderedSet and OrderedDictionary, which preserve insertion order.
Is swift-collections free to use? What license does it have?
swift-collections is open source under the Apache-2.0 license. Check the license terms before using it in commercial products.
Is swift-collections still maintained?
Actively maintained. The last commit to swift-collections was on Nov 6, 2026.
What can I use swift-collections for?
Maintaining insertion order in a Swift dictionary or set without writing custom code. Using a priority queue or double-ended queue in a Swift server or app. Storing large sets of integers or booleans more compactly with bit-based types. Sharing immutable snapshots of a dictionary across threads or states with persistent trees.
How do I install swift-collections?
Add swift-collections as a package dependency in your Package.swift, as described in the README's usage section
Where can I get swift-collections?
The source code and installation instructions are on GitHub: https://github.com/apple/swift-collections

Summary generated by AI from the project's README. GitHub stats refresh daily.

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