symbolic derivative computation

Hello folks, I would like to know if are there any tools out there that compute analytical derivatives. I heard a program that takes in input a C/C++ file and generates a C/C++ file that contains the mathematical analytical derivative of the input code. if you know of any tools that is able to generated source code with analytical derivatives please let me know. i heard of such tool at work but cannot recall the name and google did not help. Thanks! Andrea.