public func tuple<T: Equatable>(a: T?, b: T?) -> Bool {
    switch (a, b) {
    case (nil, nil): return true
    case (.some(let x), .some(let y)): return x == y
    default: break
    }
    return false
}

public func nested<T: Equatable>(a: T?, b: T?) -> Bool {
    switch a {
    case nil:
        switch b {
        case nil: return true
        default: break
        }
    case .some(let x):
        switch b {
        case .some(let y): return x == y
        default: break
        }
    }
    return false
}