---
title: "init(signOf:magnitudeOf:)"
framework: swift
role: symbol
role_heading: Initializer
path: "swift/double/init(signof:magnitudeof:)-6i9uy"
---

# init(signOf:magnitudeOf:)

Creates a new floating-point value using the sign of one value and the magnitude of another.

## Declaration

```swift
init(signOf: Self, magnitudeOf: Self)
```

## Parameters

- `signOf`: A value from which to use the sign. The result of the initializer has the same sign as signOf.
- `magnitudeOf`: A value from which to use the magnitude. The result of the initializer has the same magnitude as magnitudeOf.

## Discussion

Discussion The following example uses this initializer to create a new Double instance with the sign of a and the magnitude of b: let a = -21.5 let b = 305.15 let c = Double(signOf: a, magnitudeOf: b) print(c) // Prints "-305.15" This initializer implements the IEEE 754 copysign operation.