[swift-users] A protocol-oriented numerics library

[Xiaodi Wu]

That’s a very neat helper!


On Sat, Jun 10, 2017 at 10:12 Karl Wagner <razielim at gmail.com> wrote:

> On 10. Jun 2017, at 03:18, Xiaodi Wu via swift-users <
> swift-users at swift.org> wrote:
>
> Hi all,
>
> A few weeks ago, Joe Groff challenged users on Twitter to create a
> Rational<T> type making use of the new integer protocols implemented for
> Swift 4. As it happens, I'd already started a project to try out these new
> number protocols. Now that I think the most embarrassing bugs have been
> squashed in that project, I thought I'd share it here in case anyone else
> might find it useful.
>
> NumericAnnex <https://github.com/xwu/NumericAnnex> is meant to supplement
> the standard library's numerics facilities in Swift 4. At the moment, it
> provides:
>
> * Extensions to BinaryInteger for GCD, LCM, and exponentiation
>
> * Protocols Math (refines SignedNumeric), Real (refines Math and
> FloatingPoint), and PRNG  (refines Sequence and IteratorProtocol)
>
> * Types Complex<T>, Rational<T>, and Random
>
> Documentation is available at <https://xwu.github.io/NumericAnnex/>.
>
> I'd love to hear feedback. I'll follow up shortly on Swift Evolution with
> some thoughts on future improvements to integer protocols based on this
> experience.
>
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>
>
> It looks good.
>
> When it comes to trig functions, personally I’ve found it helpful to
> introduce an “Angle<T>” type to my own projects, rather than documenting
> “this angle expects radians” and having users do the conversion.
>
> public enum Angle<T: FloatingPoint> {
>     case degrees(T)
>     case radians(T)
>
>     public var degrees: T {
>         switch self {
>         case .degrees(let degs): return degs
>         case .radians(let rads): return (rads / .pi) * 180
>         }
>     }
>
>
>     public var radians: T {
>         switch self {
>         case .degrees(let degs): return (degs / 180) * .pi
>         case .radians(let rads): return rads
>         }
>     }
> }
>
> Allows usage such as:
>
> func rotate(by angle: Angle<CGFloat>) {
>
>    let rads = angle.radians
>    ...
> }
>
> rotate(by: .degrees(90))
> rotate(by: .radians(.pi/2))
>
>
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