How to define a type as a rebranded native type. Downside: lots of casting. Good or bad?

ewma.go

type SimpleEWMA float64

// Value returns the current value of the moving average.
func (e *SimpleEWMA) Value() float64 {
  return float64(*e)
}

// Add adds a value to the series and updates the moving average.
func (e *SimpleEWMA) Add(value float64) {
	if *e == 0 { // this is a proxy for "uninitialized"
		*e = SimpleEWMA(value)
	} else {
		*e = (SimpleEWMA(value) * SimpleEWMA(DECAY)) + (*e * (1 - SimpleEWMA(DECAY)))
	}
}

Could you use *e = SimpleEWMA(value * DECAY) + (*e * (1 - DECAY))