Polynomial band limited step

polyblep_waveforms

// phase in range 0 <= phase < 1
// pwm in range -1 <= pwm <= 1

dt = frequency / samplerate

saw(phase, dt) {
  return phase * 2 - 1 - polyBlep(phase, dt)
}

pulse(phase, dt, pwm = 0) {
  return saw(phase) - saw(wrap(phase + (pwm + 1 / 2))) + pwm
}

polyBlep(phase, dt) {
  if (phase < dt) {
    pdt = phase / dt
    return (pdt * 2) - (pdt * pdt) - 1
  }
  if (phase > 1 - dt) {
    pdt = (phase - 1) / dt
    return (pdt * pdt) + (pdt * 2) + 1
  }
  return 0
}

wrap(value) {
  while (value >= 1) {
    value -= 1
  }
  while (value < 0) {
    value += 1
  }
  return value
}