Character+Strideable.swift

extension Character: Strideable {
    public typealias Stride = Int

    public func distance(to other: Character) -> Character.Stride {
        guard let first = self.unicodeScalars.first else {
            fatalError()
        }
        guard let other = other.unicodeScalars.first else {
            fatalError()
        }

        return (Int(first.value) - Int(other.value))
    }

    public func advanced(by n: Character.Stride) -> Character {
        guard let first = self.unicodeScalars.first else {
            fatalError()
        }
        guard let scalar = UnicodeScalar(Int(first.value) + n) else {
            fatalError()
        }
        return Character(scalar)
    }
}


("A" as Character ... "Z").forEach({ print($0) })

Does it matter that line 12 can return a negative value? Seems like distance should be positive

Not exactly. If it couldn't be negative, then given the character "d" and a distance of 1, how would it know whether to go to "c" or "e"?

Ok thank you, that makes sense. ("d" as Character).advanced(by: 1) goes to "e" and then passing -1 will go to "c"