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# index(_:offsetBy:)

Returns an index that is the specified distance from the given index.

```
func index(_ i: String.UTF16View.Index, offsetBy n: Int) -> String.UTF16View.Index
```

## Parameters

`i`

A valid index of the collection.

## Return Value

An index offset by `distance` from the index `i`. If
`distance` is positive, this is the same value as the result of
`distance` calls to `index(after:)`. If `distance` is negative, this
is the same value as the result of `abs(distance)` calls to
`index(before:)`.

## Discussion

The following example obtains an index advanced four positions from a
string’s starting index and then prints the character at that position.

```
let s = "Swift"
let i = s.index(s.startIndex, offsetBy: 4)
print(s[i])
// Prints "t"
```

The value passed as `distance` must not offset `i` beyond the bounds of
the collection.

> Complexity: O(1) if the collection conforms to
> `RandomAccessCollection`; otherwise, O(*k*), where *k* is the absolute
> value of `distance`.

---

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