There are different algorithms for Element==CGPoint, Element==[CGPoint],
Element==[AreaPoint], etc…
Your second suggestion work:
protocol Inertial {
func convexHull( _ t:AffineTransform? ) -> [CGPoint]
func area( _ t:AffineTransform? ) -> CGFloat
func firstOrderMomentums( _ t:AffineTransform? ) ->
(x:CGFloat,y:CGFloat)
func secondOrderMomentums( _ t:AffineTransform? ) ->
(xx:CGFloat,xy:CGFloat,yy:CGFloat)
}
protocol InertialElement {
static func convexHull( elements:[Self], _ t: AffineTransform?) ->
[CGPoint]
static func area( elements:[Self],_ t: AffineTransform?) -> CGFloat
static func firstOrderMomentums( elements:[Self],_ t: AffineTransform?)
-> (x: CGFloat, y: CGFloat)
static func secondOrderMomentums( elements:[Self],_ t:
AffineTransform?) -> (xx: CGFloat, xy: CGFloat, yy: CGFloat)
}
extension Array : Inertial where Element : InertialElement {
func convexHull(_ t: AffineTransform?) -> [CGPoint] {
return Element.convexHull(elements: self, t)
}
func area(_ t: AffineTransform?) -> CGFloat {
return Element.area(elements: self, t)
}
func firstOrderMomentums(_ t: AffineTransform?) -> (x: CGFloat, y:
CGFloat) {
return Element.firstOrderMomentums(elements: self, t)
}
func secondOrderMomentums(_ t: AffineTransform?) -> (xx: CGFloat, xy:
CGFloat, yy: CGFloat) {
return Element.secondOrderMomentums(elements: self, t)
}
}
and than:
extension CGPoint : InertialElement {
static func convexHull( elements:[CGPoint], _ t: AffineTransform?) ->
[CGPoint] {
return ConvexHull.convexHull( points:elements ).map { $0 * t }
}
static func area( elements:[CGPoint],_ t: AffineTransform?) -> CGFloat {
return InertialUti.area( polig: elements,t )
}
static func firstOrderMomentums( elements:[CGPoint],_ t:
AffineTransform?) -> (x: CGFloat, y: CGFloat) {
return InertialUti.firstOrderMomentums( polig:elements,t )
}
static func secondOrderMomentums( elements:[CGPoint],_ t:
AffineTransform?) -> (xx: CGFloat, xy: CGFloat, yy: CGFloat) {
return InertialUti.secondOrderMomentums( polig:elements,t )
}
}
extension Array : InertialElement where Element == CGPoint {
...
}
extension AreaPoint : InertialElement {
...
}
etc...
Thanks, Slava. :-)
Antonino
> Il giorno 28 nov 2017, alle ore 23:17, Slava Pestov <spes...@apple.com> ha
> scritto:
>
> Hi Antonio,
>
> This is explicitly mentioned in the original proposal. We do not allow
> multiple conditional conformances to be defined for the same type. Instead,
> is it possible to express your conformance as follows?
>
> extension Array : Intertial where Element : Inertial { … }
>
> Or do you really need different algorithms for Element == CGPoint and Element
> == [CGPoint], with no conformance for Element == [[CGPoint]], etc?
>
> If the latter, you could possibly have an InertialElement protocol or similar
> that CGPoint and [CGPoint] conform to, with a second level of dispatch to
> pick between the two cases.
>
> Slava
>
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