# distance(from:to:) Returns the distance between two indices. ``` func distance(from start: UniqueArray.Index, to end: UniqueArray.Index) -> Int ``` ## Parameters `start` A valid index of the collection. `end` Another valid index of the collection. If end is equal to start, the result is zero. ## Return Value The distance between `start` and `end`. ## Discussion> Note: To improve performance, this method does not validate that the > given index is valid before offseting it. Index validation is > deferred until the resulting index is used to access an element. > This optimization may be removed in future versions; do not rely on it. > Complexity: O(1) --- 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)