return 0
	case -NearZero < x && x < NearZero:
		return 1 + x
	}

	// reduce; computed as r = hi - lo for extra precision.
	var k int
	switch {
	case x < 0:
		k = int(Log2e*x - 0.5)
	case x > 0:
		k = int(Log2e*x + 0.5)
	}
	hi := x - float64(k)*Ln2Hi
	lo := float64(k) * Ln2Lo

	// compute
	return expmulti(hi, lo, k)
}

// Exp2 returns 2**x, the base-2 exponential of x.
//