# init(_:) Creates a new index into a reversed collection for the position before the specified index. ``` init(_ base: Base.Index) ``` ## Parameters `base` The position after the element to create an index for. ## Discussion When you create an index into a reversed collection using `base`, an index from the underlying collection, the resulting index is the position of the element *before* the element referenced by `base`. The following example creates a new `ReversedIndex` from the index of the `"a"` character in a string’s character view. ``` let name = "Horatio" let aIndex = name.firstIndex(of: "a")! // name[aIndex] == "a" let reversedName = name.reversed() let i = ReversedCollection.Index(aIndex) // reversedName[i] == "r" ``` The element at the position created using `ReversedIndex<...>(aIndex)` is `"r"`, the character before `"a"` in the `name` string. --- 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)