---
title: "init(exactly:)"
framework: swift
role: symbol
role_heading: Initializer
path: "swift/int128/init(exactly:)-3o2o0"
---

# init(exactly:)

Creates a new instance from the given integer, if it can be represented exactly.

## Declaration

```swift
init?<T>(exactly source: T) where T : BinaryInteger
```

## Parameters

- `source`: A value to convert to this type.

## Discussion

Discussion If the value passed as source is not representable exactly, the result is nil. In the following example, the constant x is successfully created from a value of 100, while the attempt to initialize the constant y from 1_000 fails because the Int8 type can represent 127 at maximum: let x = Int8(exactly: 100) // x == Optional(100) let y = Int8(exactly: 1_000) // y == nil