puttin

struct RecurrenceRelation<Element>: SequenceType, GeneratorType {
  
  private var prevs: [Element]
  private let relat: ([Element], Int) -> Element
  private var i: Int = 0
  
  mutating func next() -> Element? {
    guard i == prevs.endIndex else { return prevs[i++] }
    prevs.append(relat(prevs, i))
    prevs.removeAtIndex(0)

puttin

#import <objc/runtime.h>
#import <Foundation/Foundation.h>


@interface Person : NSObject
@end
@implementation Person
@end

@interface Person(dynamicProperties)