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# significandBitCount

The available number of fractional significand bits.

```
static var significandBitCount: Int { get }
```

## Discussion

For fixed-width floating-point types, this is the actual number of
fractional significand bits.

For extensible floating-point types, `significandBitCount` should be the
maximum allowed significand width (without counting any leading integral
bit of the significand). If there is no upper limit, then
`significandBitCount` should be `Int.max`.

Note that `Float80.significandBitCount` is 63, even though 64 bits are
used to store the significand in the memory representation of a
`Float80` (unlike other floating-point types, `Float80` explicitly
stores the leading integral significand bit, but the
`BinaryFloatingPoint` APIs provide an abstraction so that users don’t
need to be aware of this detail).

---

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