// sRGB parameters
enum a = 1.055;
enum b = 0.0031308;
enum s = 12.92;
enum e = 2.4;

double v = 0.5;

// the gamma function
if (v <= b*s)
    v = v/s;
else
    v = ((v + (a - 1)) / a)^^e;

assert(abs(v - hybridGammaToLinear!(a, b, s, e)(0.5)) < double.epsilon);