Convert RGB to L*ab color space in Swift

rgb_to_lab.swift

//http://stackoverflow.com/a/24201042/83859

infix operator ^^ { }
func ^^ (radix: Double, power: Double) -> Double {
    return Double(pow(Double(radix), Double(power)))
}

//Based on https://github.com/d3/d3-color/blob/master/src/lab.js

let Kn:Double = 18,
Xn:Double = 0.950470, // D65 standard referent
Yn:Double = 1,
Zn:Double = 1.088830,
t0:Double = 4 / 29,
t1:Double = (6 / 29),
t2:Double = 3 * t1 * t1,
t3:Double = t1 * t1 * t1;


func rgb2xyz(x:Double) -> Double {
    let val = x/255;
    if val <= 0.04045
    { return (val / 12.92)}
    else { return ((val + 0.055) / 1.055^^2.4); }
}

func xyz2lab(tee:Double) -> Double{
    if tee > t3 { return (tee^^(1/3));}
    else { return tee / t2 + t0 ;}
}
    
func rgb_to_lab(red:Double, green:Double, blue:Double) ->  (Double, Double, Double)
{
    let b = rgb2xyz(red),
    a = rgb2xyz(green),
    l = rgb2xyz(blue),
    x = xyz2lab((0.4124564 * b + 0.3575761 * a + 0.1804375 * l) / Xn),
    y = xyz2lab((0.2126729 * b + 0.7151522 * a + 0.0721750 * l) / Yn),
    z = xyz2lab((0.0193339 * b + 0.1191920 * a + 0.9503041 * l) / Zn);
    return (116 * y - 16, 500 * (x - y), 200 * (y - z))
}

Is this updated for swift3?