Long Double in Swift

Question

In C, there is a type called long double, which on my machine is 16-bytes (128-bit). Is there any way to store a long double in Swift? I've tried type aliases (typedefs) of long double from an Objective-C header, but it doesn't show up in Swift. And functions returning long double (powl, sqrtl) don't show up neither.

I know there's a Float80 but that's only 80 bits, not 128 bits.

Are you sure is 128bits? From the official docs: **long double** - extended precision floating point type. Does not necessarily map to types mandated by IEEE-754. **Usually 80-bit** x87 floating point type on x86 and x86-64 architectures. — Daniel Illescas, Jul 04 '17 at 11:04
Well, you can use Float80 or some custom integer types like https://github.com/Jitsusama/UInt128 or https://github.com/CryptoCoinSwift/UInt256 — Daniel Illescas, Jul 04 '17 at 11:22
I tried to make a function that return a `long double` from C but Swift doesn't recognise the function, and it happens the same with a variable, so you can't use C long double in Swift. — Daniel Illescas, Jul 04 '17 at 12:02

score 4 · Accepted Answer · answered Jul 04 '17 at 11:05

4

Unless you have a POWER processor, your 128 bit long double is actually an 80 bits extended precision number, plus 48 bit wasted.

answered Jul 04 '17 at 11:05

gnasher729

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Long Double in Swift

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