I'm writing a calculator program for fun that takes an input from a user, via typed commands. So far, it works very well with basic ^*/+- arithmetic, however, I want to start adding functions, such as sin(45) or ln(e) and, eventually, variables to the expressions it solves. How would one do that? I don't have any code for that purpose as I don't know how or where to start for that. If there is some code you'd like to see that would help, please ask for it, as I don't know what would help and there is too much code to post it all.

Attached is what I have now.Calculator.zip