This is a calculator where you can enter an expresion to be evaluated. For example:

3+2*3-(1+1)
The result is 7

You can use some maths functions like sin,cos,tan... There are some constats defined aswell (pi, euler...)

sin(pi) + 3 - euler * (4 - 2)
The result is 6.12704

This code was a proof of concept. It was done some years ago (2013?). I hadn't even started my degree yet, so you won't see any popular algorithm. Instead, there are a lot of work arounds for try to solve the problem.

But... It works great! Even when you don't know the theory, you can find a solution with cleverness. That's why i like this code.