fixifpossible.swift

//----------------------------------------------------------------------------------------------------
// This program compiles and runs. Question: Can generic struct X be made to satisfy TEST?
//----------------------------------------------------------------------------------------------------
protocol DefaultInitializable { init() }
extension Double : DefaultInitializable {}
extension Float  : DefaultInitializable {}
extension Int    : DefaultInitializable {}
extension UInt8  : DefaultInitializable {}
// ...
protocol CountType { static var value: Int { get } }
struct Count0 : CountType { static var value: Int { return 0 } }
struct CountSuccessorOf<T: CountType> : CountType { static var value: Int { return T.value + 1 } }
extension CountType {
    typealias Plus1 = CountSuccessorOf<Self>
    typealias Plus2 = Plus1.Plus1
    typealias Plus3 = Plus1.Plus2
    typealias Plus4 = Plus1.Plus3
    // ...
}
typealias Count1 = Count0.Plus1
typealias Count2 = Count0.Plus2
typealias Count3 = Count0.Plus3
typealias Count4 = Count0.Plus4
// ...
//----------------------------------------------------------------------------------------------------
// X (HOWTODO)
//----------------------------------------------------------------------------------------------------
struct X<C: CountType, E: DefaultInitializable> { // X must be parameterized by Count and Element.
    typealias Count = C
    typealias Element = E
    //eg var storage: SomethingThatWillMakeXHaveTheSizeOfCountElements
}
//----------------------------------------------------------------------------------------------------
// TEST
//----------------------------------------------------------------------------------------------------
typealias SomeCount = Count4 // Or Count3, or Count0, or Count4.Plus4.Plus4, ...
typealias SomeElement = Double // Or Int, or Float, or UInt8, ...
typealias SomeX = X<SomeCount, SomeElement>
let currentStride = strideof(SomeX)
let correctStride = SomeCount.value * strideof(SomeElement)
print("Current stride:", currentStride)
print("Correct stride:", correctStride)
if currentStride == correctStride {
    print("X works for Element \(SomeElement.self) and Count \(SomeCount.value)")
} else {
    print("X is not working ...")
}
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