Sorry, mostly I was just commenting on what I now see was an incorrect
interpretation of the “// but something actually requiring high precision ...”
comment in your example code. I’d read it as... you know, I’m not sure what I’d
though it said... I think something that implied the code would convert the
`Float80` data to another format with higher precision.
My mistake for not reading more carefully before replying.
- Dave Sweeris
> On Dec 3, 2017, at 15:22, Jens Persson <j...@bitcycle.com> wrote:
>
> I'm not sure what you mean David. That function was just part of my attempt
> at presenting a solution to Antonino's question (that particular function is
> from Antonino's code).
> Below is my solution to Antonino's problem again, including a perhaps clearer
> comment in that function:
>
> protocol Float80Convertible : BinaryFloatingPoint {
> init(_ value: Float80)
> var float80: Float80 { get }
> }
> extension Double : Float80Convertible {
> var float80: Float80 { return Float80(self) }
> }
> extension Float : Float80Convertible {
> var float80: Float80 { return Float80(self) }
> }
>
> func maxPrecisionCalculation(input:Float80) -> Float80 {
> return inpu
> // In the actual use case, this would of course not just
> // return input. Instead it would perform some computation
> // that (in contrast to just returning input) actually needs
> // the high precision of Float80.
> }
>
> func someComplexCalculation<T:Float80Convertible>(input: T) -> T {
> let input80 = input.float80
> let output80 = maxPrecisionCalculation(input: input80)
> return T(output80)
> }
>
> /Jens
>
>
>> On Fri, Dec 1, 2017 at 11:59 PM, David Sweeris <daveswee...@mac.com> wrote:
>>
>>
>>> On Dec 1, 2017, at 13:18, Jens Persson via swift-users
>>> <swift-users@swift.org> wrote:
>>>
>>> func maxPrecisionCalculation(input:Float80) -> Float80 {
>>> return input // but something actually reauiring high precision ...
>>> }
>>
>> AFAIK, Float80 is the high precision format on macOS (well, Intel macs,
>> anyway... can’t recall if Swift can target OSs old enough to run on PPC
>> macs). I’d avoid using it, though. AFAIK it’s an x86-only format (it might
>> even be Intel-only... 5-10 minutes of googling didn’t give me a clear answer
>> on whether AMD’s CPUs support it).
>>
>> I don’t know what we do with it on ARM targets, and I’m not at my computer
>> to try to figure out.
>>
>> Unless maybe the x86 or ARM vector extensions support 128 or 256 bit floats?
>> I don’t think they do, but I’m not 100% on that.
>>
>> - Dave Sweeris
>
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