`I've recently started an easing/interpolation family of function`

`in my D user library. It's based on something I know well since`

`I've already used them in 2012 in a VST plugin called GrainPlot`

`(RIP).`

`However for one of the function, I can't manage to get the`

`inverse.`

## Advertising

A function that's fully implemented: https://github.com/BBasile/iz/blob/master/import/iz/math.d#L598 - f(x,c) = x*x*x - x*x*c + x*c; - c(f(0.5)) = 4 * (y - 0.125)); Another: https://github.com/BBasile/iz/blob/master/import/iz/math.d#L749 - f(x,c) = pow(x, c); - c(f(0.5)) = log(y) / log(0.5)); The problem is here: https://github.com/BBasile/iz/blob/master/import/iz/math.d#L849 - f(x,c) = 1.0 - pow(1.0 - pow(x, 2.0/c), c * 0.5); - c(f0.5)) = ? Which means that I ask you if you can isolate c for y = 1.0 - pow(1.0 - pow(0.5, 2.0/c), c * 0.5); y is always f(0.5,c)