# init(exactly:) Creates a new instance from the given integer, if it can be represented exactly. ``` init?(exactly source: T) where T : BinaryInteger ``` ## Parameters `source` A value to convert to this type. ## 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 ``` --- 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)