RxFibonacci

Hoge.java

// in android :p
  private void printFib(int l) {
    fib(l).subscribe(new Action1<List<Long>>() {
      @Override
      public void call(List<Long> fib) {
        Log.v(TAG, fib.toString());
      }
    });
  }

  private Observable<List<Long>> fib(int l) {
    // f(n-2)
    final BehaviorSubject<Long> s2 = BehaviorSubject.create();
    // f(n-1)
    final BehaviorSubject<Long> s1 = BehaviorSubject.create();

    final Observable<Long> f2 = s2.startWith(0L, 1L).doOnNext(new Action1<Long>() {
      @Override
      public void call(Long t) {
        Log.v("f(n-2)", t.toString());
      }
    });

    final Observable<Long> f1 = s1.startWith(0L, 0L).doOnNext(new Action1<Long>() {
      @Override
      public void call(Long t) {
        Log.v("f(n-1)", t.toString());
        s2.onNext(t);
      }
    });
    return Observable.zip(f1, f2, new Func2<Long, Long, Long>() {
      @Override
      public Long call(Long n1, Long n2) {
        return n1 + n2;
      }
    }).doOnNext(new Action1<Long>() {
      @Override
      public void call(Long t) {
        s1.onNext(t);
      }
    }).take(l).toList();
  }