better.go

func smallOkay(x, z float64) (float64, float64, bool) {
	for x < 0 {
		if x > -1e-09 {
			return x, z, true
		}
		z = z / x
		x = x + 1
	}
	for x < 2 {
		if x < 1e-09 {
			return x, z, true
		}
		z = z / x
		x = x + 1
	}
	return x, z, false
}

func stuff(x float64) float64 {
	z := 1.0

        for x >= 3 {
                x = x - 1
                z = z * x
        }
	x, z, smallFastPath := smallOkay(x, z)
	if smallFastPath {
		if x == 0 {
			return Inf(1)
		}
		return z / ((1 + Euler*x) * x)
	}
	if x == 2 {
		return z
	}

	x = x - 2
	p = (((((x*_gamP[0]+_gamP[1])*x+_gamP[2])*x+_gamP[3])*x+_gamP[4])*x+_gamP[5])*x + _gamP[6]
	q = ((((((x*_gamQ[0]+_gamQ[1])*x+_gamQ[2])*x+_gamQ[3])*x+_gamQ[4])*x+_gamQ[5])*x+_gamQ[6])*x + _gamQ[7]
	return z * p / q
}