---
title: "init(sign:exponent:significand:)"
framework: swift
role: symbol
role_heading: Initializer
path: "swift/floatingpoint/init(sign:exponent:significand:)"
---

# init(sign:exponent:significand:)

Creates a new value from the given sign, exponent, and significand.

## Declaration

```swift
init(sign: FloatingPointSign, exponent: Self.Exponent, significand: Self)
```

## Parameters

- `sign`: The sign to use for the new value.
- `exponent`: The new value’s exponent.
- `significand`: The new value’s significand.

## Discussion

Discussion The following example uses this initializer to create a new Double instance. Double is a binary floating-point type that has a radix of 2. let x = Double(sign: .plus, exponent: -2, significand: 1.5) // x == 0.375 This initializer is equivalent to the following calculation, where ** is exponentiation, computed as if by a single, correctly rounded, floating-point operation: let sign: FloatingPointSign = .plus let exponent = -2 let significand = 1.5 let y = (sign == .minus ? -1 : 1) * significand * Double.radix ** exponent // y == 0.375 As with any basic operation, if this value is outside the representable range of the type, overflow or underflow occurs, and zero, a subnormal value, or infinity may result. In addition, there are two other edge cases: If the value you pass to significand is zero or infinite, the result is zero or infinite, regardless of the value of exponent. If the value you pass to significand is NaN, the result is NaN. For any floating-point value x of type F, the result of the following is equal to x, with the distinction that the result is canonicalized if x is in a noncanonical encoding: let x0 = F(sign: x.sign, exponent: x.exponent, significand: x.significand) This initializer implements the scaleB operation defined by the IEEE 754 specification.