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# significand

The significand of the floating-point value.

```
var significand: Self { get }
```

## Discussion

The magnitude of a floating-point value `x` of type `F` can be calculated
by using the following formula, where `**` is exponentiation:

```
x.significand * (F.radix ** x.exponent)
```

In the next example, `y` has a value of `21.5`, which is encoded as
`1.34375 * 2 ** 4`. The significand of `y` is therefore 1.34375.

```
let y: Double = 21.5
// y.significand == 1.34375
// y.exponent == 4
// Double.radix == 2
```

If a type’s radix is 2, then for finite nonzero numbers, the significand
is in the range `1.0 ..< 2.0`. For other values of `x`, `x.significand`
is defined as follows:

- If `x` is zero, then `x.significand` is 0.0.
- If `x` is infinite, then `x.significand` is infinity.
- If `x` is NaN, then `x.significand` is NaN.

> Note: The significand is frequently also called the *mantissa*, but
> significand is the preferred terminology in the 
> [IEEE 754
> specification](http://ieeexplore.ieee.org/servlet/opac?punumber=4610933), to allay confusion with the use of mantissa for
> the fractional part of a logarithm.

---

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