MathRPN

MathRPN is really a sweet RPN Calculator. Unlike others that limit your ability to interact with the rest of the stack, MathRPN lets you operate on any set of selected stack rows and use your operation of choice. Number formatting preferences and stack AutoSave complement its functionality, as well as the versatile regular expression engine that allows you to evaluate mathematical expressions in any application, via its service, and use user-defined functions and constants directly with the stack. MathRPN now also includes some graphing support.