# WordPair A pair of two word sized `UInt`s. ``` @frozen struct WordPair ``` ## Overview This type’s primary purpose is to be used in double wide atomic operations. On platforms that support it, atomic operations on `WordPair` are done in a single operation for two words. Users can use this type as itself when used on `Atomic`, or it could be used as an intermediate step for custom `AtomicRepresentable` types that are also double wide. ``` let atomicPair = Atomic(WordPair(first: 0, second: 0)) atomicPair.store(WordPair(first: someVersion, second: .max), ordering: .relaxed) ``` When used as an intermediate step for custom `AtomicRepresentable` types, it is critical that their `AtomicRepresentation` be equal to `WordPair.AtomicRepresentation`. ``` struct GridPoint { var x: Int var y: Int } extension GridPoint: AtomicRepresentable { typealias AtomicRepresentation = WordPair.AtomicRepresentation ... } ``` > Note: This type only conforms to `AtomicRepresentable` on platforms that > support double wide atomics. ## Topics ### Initializers [`init(first: UInt, second: UInt)`](/documentation/Synchronization/WordPair/init(first:second:)) Initialize a new `WordPair` value given both individual words. ### Instance Properties [`var first: UInt`](/documentation/Synchronization/WordPair/first) The first element in this word pair. [`var second: UInt`](/documentation/Synchronization/WordPair/second) The second element in this word pair. ### Default Implementations [AtomicRepresentable Implementations](/documentation/Synchronization/WordPair/AtomicRepresentable-Implementations) [CustomDebugStringConvertible Implementations](/documentation/Synchronization/WordPair/CustomDebugStringConvertible-Implementations) [CustomStringConvertible Implementations](/documentation/Synchronization/WordPair/CustomStringConvertible-Implementations) [Equatable Implementations](/documentation/Synchronization/WordPair/Equatable-Implementations) [Hashable Implementations](/documentation/Synchronization/WordPair/Hashable-Implementations) ## Relationships ### Conforms To [`CustomStringConvertible`](/documentation/Swift/CustomStringConvertible) [`Equatable`](/documentation/Swift/Equatable) [`AtomicRepresentable`](/documentation/Synchronization/AtomicRepresentable) [`Hashable`](/documentation/Swift/Hashable) [`CustomDebugStringConvertible`](/documentation/Swift/CustomDebugStringConvertible) [`BitwiseCopyable`](/documentation/Swift/BitwiseCopyable) [`Sendable`](/documentation/Swift/Sendable) [`Copyable`](/documentation/Swift/Copyable) [`Escapable`](/documentation/Swift/Escapable) [`Comparable`](/documentation/Swift/Comparable) [`SendableMetatype`](/documentation/Swift/SendableMetatype) --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)