I'd like to use a CAMediaTimingFunction (e.g. kCAMediaTimingFunctionEaseIn) to map an input value (0-1) to an output value (0-1), just like [the docs](https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/CAMediaTimingFunction_class/Introduction/Introduction.html) say this class does. However, this functionaity doesn't appear to be exposed at all. 

Is there some way I can access this functionality for my own custom values? This is not in a UIView, CALayer etc - it's just in some custom code where I'd like to use the iOS curves.