Smooth and Gaussian Curve

Takes a linear 0-1 value and apply an S-function. Gauss is the inverse of that S-function.

function smooth_curve(a) =
let (b = clamp(a))(b * b * (3 - 2 * b));

function clamp(a, b = 0, c = 1) = min(max(a, b), c);

function gauss(x) =  
     x + (x - smooth_curve(x));