prev := s.buf[s.idx]
	s.buf[s.idx] = next

	if s.filledBuf {
		s.prevSMA += (next - prev) / float64(s.window)
		s.CAvg += (next - s.CAvg) / float64(s.window)
	} else {
		s.CAvg = s.simpleMovingAvg()
		s.prevSMA = s.CAvg
	}
	if s.idx == s.window-1 {
		s.filledBuf = true
	}
	s.idx = (s.idx + 1) % s.window
}

func (s *SMA) simpleMovingAvg() float64 {
	if s.filledBuf {
		return s.prevSMA
	}