Answer to Ch 6 Q3 - using switch.

[yeaweeyum]

Code: (Objective-C)

#import <Foundation/Foundation.h>

//interface section

@interface Calculator : NSObject
{
	double accumulator;
}

-(void) setAccumulator: (double) value;
-(void) clear;
-(double) accumulator;
-(void) endOfCalc;

-(void) add: (double) value;
-(void) subtract: (double) value;
-(void) multiply: (double) value;
-(void) divide: (double) value;

@end

//implementation section

@implementation Calculator

-(void) setAccumulator: (double) value
{
	accumulator = value;
}

-(void) clear
{
	accumulator = 0;
}

-(double) accumulator
{
	return accumulator;
}

-(void) endOfCalc
{
	NSLog(@"Job Done! Final answer is = %f", accumulator);
}

-(void) add: (double) value
{
	accumulator += value;
}

-(void) subtract: (double) value
{
	accumulator -= value;
}

-(void) multiply: (double) value
{
	accumulator *= value;
}

-(void) divide: (double) value
{
	accumulator /= value;
}

@end

//program section

int main (int argc, const char * argv[])
{
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	double value;
	char op;
	Calculator *deskCalc =[[Calculator alloc] init];
	
	do 
	{
		NSLog (@"Type value:");
		scanf ("%lf", &value);
		
		NSLog (@"Type operator:");
		scanf (" %c", &op);
		
		switch (op) 
		{
			case 'S':
				[deskCalc setAccumulator: value];
				break;
				
			case '+':
				[deskCalc add: value];
				break;
				
			case '-':
				[deskCalc subtract: value];
				break;
				
			case '*':
				[deskCalc multiply: value];
				break;
				
			case '/':
				if (value !=0)
				{
					[deskCalc divide: value];
				}
				else {
					NSLog(@"DO NOT DIVIDE BY ZERO!! COME ON!!");
				}

				break;	
				
			case 'E':
				[deskCalc endOfCalc];
				break;
				
			default:
				NSLog(@"Unknown Operator");
				break;
		}
	}
	while (op !='E');

		

    [pool drain];
    return 0;
}