In my experience, LaTeX is not really a worthy alternative to writing formulas by hand. Sure, you should absolutely use LaTeX for typesetting mathematical reports and the like, but LaTeX does not stand a chance against pen and paper when it comes to taking notes or doing calculations. The world needs tooling that is much more similar to writing formulas on a paper in its interface. At the moment, I also fail to see any benefit at all in using laptops in mathematics education.
Swift looks promising and looks like a step in the right direction. However, looking at the reference and everything, I fail to find an answer to this question. Does the concept of private members (methods and variables) in Swift's object system not exist? It looks like every single variable is exposed fully without any way to prevent it from being so.