In this mode, the GUI has a button for each of the arithmetic and stack operations listed below. It also has a button for each digit, a number's sign, a decimal point, and a button used to terminate a number. The calculator will work with floating point numbers. Use the types double and Double . It is an error if there are fewer than two items on the stack.
R rolls the stack down one position.
You must use the provided IDeque interface. Arrays and CList s are both natural candidates for the underlying data structure. The calculator will have a GUI interface for entering numbers and the above operations. It will also have a way to swap between expression and immediate mode, without changing the stack contents. In each mode, the irrelevant GUI features should be disabled.