Returns the size of an ulp (unit in last place) for d. If d is ##NaN => ##NaN If d is ##Inf or ##-Inf => ##Inf If d is zero => Double/MIN_VALUE If d is +/- Double/MAX_VALUE => 2^971 See: https://docs.oracle.com/javase/8/docs/api/java/lang/Math.html#ulp-double-