[swift-evolution] Missing initializers from/to FloatingPointType

[Max Moiseev]

Hi Dan,

New protocols are in the making for both integers and floating point numbers.

You particular problem is addressed here: https://github.com/stephentyrone/swift/commits/floating-point-revision

max

> On Mar 30, 2016, at 6:36 AM, Dan Raviv via swift-evolution <swift-evolution at swift.org> wrote:
> 
> While FloatingPointType can be initialized from various Int type variants, it seems to be missing an initializer from Double/Float. Similarly, there are no initializers from FloatingPointType to Double/Float. Is this intentional?
> 
> I've tried implementing the following:
> 
> // https://en.wikipedia.org/wiki/Window_function#Tukey_window <https://en.wikipedia.org/wiki/Window_function#Tukey_window>
> public func tukeyWindowFunc(index: Int, N: Int) -> Double {
>     let L = N/8
>     let indexAbs = min(index, N-1-index)
>     if indexAbs >= L {
>         return 1.0
>     }
>     else {
>         let r = Double(indexAbs) / Double(L)
>         return 0.5*(1.0 + cos(M_PI * (r - 1.0)))
>     }
> }
> 
> extension Array where Element: FloatingPointType {
>     public func tukeyWindowArray() -> [Element] {
>         return (0..<count).map{self[$0] * tukeyWindowFunc($0, N: count)}
>     }
> }
> 
> The extension failed to compile no matter how I spun it, since Double and FloatingPointType can't multiply each other and neither type can be cast to the other.
> 
> I would settle for extending just Array<Double>, but that isn't supported yet either ;)
> 
> Cheers,
> Dan
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