This is my attempt in our competition. While not so fancy it is a pretty handy calculator. As seen in the following screen shots, the calculator parses the complete formula and allows you to write expressions. It also keeps a log with all the calculations done. Using the clipboard methods you can copy calculations from the log to the input field. 'A' - Represents the last answer. 'An' - Represents the nth answer. The code is almost not documented. Feel free to ask any question about the code.