Write a big-inteter calculator program

Solution Preview

Calculator
As a demonstration of how to customize the framework, we present a simple calculator. Here are
the basic commands:
C:PearceJPOPconsole>java Calculator

type "help" for commands
-> help
Console Help Menu:
about: displays application information
help: displays this message
quit: terminate application
ARG1 + ARG2 = sum of ARG1 and ARG2
ARG1 * ARG2 = product of ARG1 and ARG2
ARG1 - ARG2 = difference of ARG1 and ARG2
ARG1 / ARG2 = quotient of ARG1 and ARG2
Note 1: Spaces between tokens are required
Note 2: ARG1 & ARG2 are numbers.
The about command displays information about the framework and the customization:
-> about
Console Framework
copyright (c) 2001, all rights reserved

A Simple Calculator
Copyright (c) 2001, all rights reserved
Of course we can do arithmetic and small errors don't break the calculator:
-> -13 + 51
result = 38.0
-> 12 / 0
Application error, can't divide by 0
-> 13.8 * 3.1416
result = 43.35408
-> x + 2
Application error, ARG1 & ARG2 must be numbers
-> quit
bye
The Console Framework
Design
The console framework provides two classes: Console and AppError. All application-specific errors discovered in the customization are handled by throwing an AppError. The Console class supplies a control loop, and overridable help(), about() , handle(), and execute() methods. In fact, execute() is abstract, ...