Equation parser

I''m looking for a tutorial on parsing a string into an equation, hopefully handling variables (maybe just x) and trigonometric functions. The end goal should also be able to solve for y and graph, but I''m not picky at this point. I''m really interested in finding stuff, but my 2 second google didn''t turn up much . Anybody know anything about this? -------------------------------------------------------- Life would be so much easier if we could just get the source code.