Is half half damage quartered or halved?

@McCrayHollisIf damage from an effect is halved twice, i.e. once from making a save and once for resistance, is it quartered, or just halved? quartered in that case

— Mike Mearls (@mikemearls) December 13, 2015

<

@McCrayHollis resistance applies only once

— Mike Mearls (@mikemearls) December 13, 2015