# difference(from:by:) Returns the difference needed to produce this collection’s ordered elements from the given collection, using the given predicate as an equivalence test. ``` func difference(from other: C, by areEquivalent: (C.Element, Self.Element) -> Bool) -> CollectionDifference where C : BidirectionalCollection, Self.Element == C.Element ``` ## Parameters `other` The base state. `areEquivalent` A closure that returns a Boolean value indicating whether two elements are equivalent. ## Return Value The difference needed to produce the receiver’s state from the parameter’s state. ## Discussion This function does not infer element moves. If you need to infer moves, call the `inferringMoves()` method on the resulting difference. > Complexity: Worst case performance is O(*n* * *m*), where *n* is the > count of this collection and *m* is `other.count`. You can expect > faster execution when the collections share many common elements. --- 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)