> Am 21.11.2017 um 02:39 schrieb Kelvin Ma via swift-evolution
> <swift-evolution@swift.org>:
>
> when SE-185 went through swift evolution, it was agreed that the next logical
> step is synthesizing these conformances for tuple types, though it was left
> out of the original proposal to avoid mission creep. I think now is the time
> to start thinking about this. i’m also tacking on Comparable to the other two
> protocols because there is precedent in the language from SE-15 that tuple
> comparison is something that makes sense to write.
>
> EHC conformance is even more important for tuples than it is for structs
> because tuples effectively have no workaround whereas in structs, you could
> just manually implement the conformance. this is especially relevant in
> graphics and scientific contexts where tuples are used to represent color
> values and points in 2D or 3D space. today you still can’t do things like
>
> let lattice = Dictionary<(Int, Int, Int), AssociatedValue>() .
>
> the commonly suggested “workaround”, which is to “upgrade” the tuple to a
> struct is problematic for two reasons:
>
> 1. it defeats the purpose of having tuples in the language
>
> 2. tuples are a logical currency type for commonly used types like points and
> vectors. If every library defined its own custom point/vector types we would
> soon (already?) have a nightmare situation where no geometry/graphics library
> would be compatible with any other geometry/graphics library, at least not
> without a lot of annoying, let alone wasteful swizzling and manual conversion
> routines in the main application.
Actually I don't think that tuples should be used for points and vectors at
all, because I prefer to differentiate these two concepts which requires
nominal types, e.g.
struct Point {
func distance(to point: Point) -> Vector
func offsetBy(_ offset: Vector) -> Point
}
Notwithstanding this disagreement I too think that EHC conformance for tuples
would be useful.
-Thorsten
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