---
title: "distance(from:to:)"
framework: swift
role: symbol
role_heading: Instance Method
path: "swift/substring/unicodescalarview/distance(from:to:)"
---

# distance(from:to:)

Returns the distance between two indices.

## Declaration

```swift
func distance(from start: Substring.UnicodeScalarView.Index, to end: Substring.UnicodeScalarView.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

Return Value The distance between start and end. The result can be negative only if the collection conforms to the BidirectionalCollection protocol.

## Discussion

Discussion Unless the collection conforms to the BidirectionalCollection protocol, start must be less than or equal to end. note: O(1) if the collection conforms to RandomAccessCollection; otherwise, O(k), where k is the resulting distance.