Programming in Objective-C, Sixth Edition

A Calculator Class

It’s time now to define a new class. We’re going to make a Calculator class, which will be a simple four-function calculator you can use to add, multiply, subtract, and divide numbers. Similar to a regular calculator, this one must keep track of the running total, or what’s usually called the accumulator. So, methods must let you set the accumulator to a specific value, clear it (or set it to zero), and retrieve its value when you’re done. Program 4.6 includes the new class definition and a test program to try your calculator.

Program 4.6

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// Implement a Calculator class#import <Foundation/Foundation.h>@interface Calculator: NSObject// accumulator methods-(void)   setAccumulator: (double) value; ...