Parsing the arithmetic expression is a classical programming exercise. It involves recursion, text processing and AI. I have chosen Delphi as a language for this example because I already had a piece of great code written in Turbo Pascal implementing 3D diagram drawing so the fusion of that and the parser allowing to enter the formula of function of two variables created a nice program to draw some nice 3D landscapes described by math formulas.
Go to 3D Plot page.