a programming project

I want to write a program that receive a mathematical expression including "tan","sin","cos","cot","ln","+","-","*","/","power""d_x(derivative)" and any other function that user defines it in a seperate file and calculate the result.
as far as I now I must use "token" method and for derivative of a function I must use tree_method structure.
I thanks anyone that can help me as soon as possible in the algorithm of the project!