---
title: UInt128.Words.Index
framework: swift
role: symbol
role_heading: Type Alias
path: swift/uint128/words-swift.struct/index
---

# UInt128.Words.Index

A type that represents a position in the collection.

## Declaration

```swift
typealias Index = Int
```

## Discussion

Discussion Valid indices consist of the position of every element and a “past the end” position that’s not valid for use as a subscript argument.