SwiftStrongTyping-DistanceTimeVelocity

DistanceTimeVelocity.swift

// Playground - noun: a place where people can play


struct Distance {
    let value: Double
}

struct Time {
    let value: Double
}

struct Velocity {
    let value: Double
    
    init(distance: Distance, time: Time) {
        value = distance.value / time.value
    }
}

// Verbose
let d1 = Distance(value: 100.0)
let t1 = Time(value: 10.0)
let v1 = Velocity(distance: d1, time: t1)
// 'Velocity' is not convertible to 'Distance'
let vv1 = Velocity(distance: v1, time: t1)


extension Double {
    func asDistance() -> Distance {
        return Distance(value: self)
    }
    func asTime() -> Time {
        return Time(value: self)
    }
}

func /(left: Distance, right: Time) -> Velocity {
    return Velocity(distance: left, time: right)
}


// Less verbose
let d2 = 100.0.asDistance()
let t2 = 10.0.asTime()
let v2 = d2 / t2
// Cannot invoke '/' with an argument list of type '(Velocity, Time)'
let vv2 = v2 / t2

// Any better way?

Is there a way to do strong type checking like this without boxing the values inside structs?