4.9 Solution

[Jason]

Code: (Objective-C)

#import <Foundation/Foundation.h>

@interface Calculator : NSObject
{
	double accumulator;
}

// Accumulator methods
-(void) setAccumulator: (double) value;
-(void) clear;
-(double) accumulator;

// Arithmetic methods
-(double) add: (double) value;
-(double) subtract: (double) value;
-(double) multiply: (double) value;
-(double) divide: (double) value;

// Additional methods
-(double) changeSign; // change sign of accumulator
-(double) reciprocal; // 1/accumulator
-(double) xSquared; // accumulator sqaured
@end

@implementation Calculator

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

-(void) clear
{
	accumulator = 0;
}

-(double) accumulator
{
	return accumulator;
}

// Arithmetic methods
-(double) add: (double) value
{
	accumulator += value;
	return accumulator;
}

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

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

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

// Additional methods
-(double) changeSign
{
	accumulator = 100.0;
	return  -1 * accumulator;
}

-(double) reciprocal
{
	accumulator = 100.0;
	return  1 / accumulator;
}

-(double) xSquared
{
	accumulator = 100.0;
	return accumulator * accumulator;
}
 
@end



int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	Calculator *deskCalc = [[Calculator alloc] init];
	
	// Set accumulator
	[deskCalc clear];
	NSLog(@"The accumulator has been cleared to: %g", [deskCalc accumulator]);
	[deskCalc setAccumulator: 100.0];
	NSLog(@"The accumulator value has been set to: %g", [deskCalc accumulator]);
	// Arithmetic methods
	NSLog(@"+ 50 = %g",[deskCalc add: 50.0]);
	NSLog(@"- 25 = %g",[deskCalc subtract: 25.0]);
	NSLog(@"x 10 = %g",[deskCalc multiply: 10.0]);
	NSLog(@"/ 5 = %g",[deskCalc divide: 5.0]);
	// Additional methods
	[deskCalc clear];
	NSLog(@"The opposite of +100 is: %g",[deskCalc changeSign]);
	NSLog(@"The reciprocal of 100 is: %g",[deskCalc reciprocal]);
	NSLog(@"100 squared is: %g", [deskCalc xSquared]);
	
	[deskCalc release];
	
    [pool drain];
    return 0;
}

[skochan]

Hi,

Your changeSign, xSquared, and reciprocal methods should also be setting the accumulator.

Cheers,

Steve Kochan

[Jason]

I changed the additional methods, thank you for letting me know Steve.

Cheers!

[dbendixen]

I wasn't setting the accumulator either, until I read this.

Code: (Objective-C)

#import <Foundation/Foundation.h>
/* This exercise builds on example 4.6 by making the arithmetic
 methods return values instead of just doing math and saving the
 result to accumulator.  So, the returned double value could be
 used in another expression. 
*/


@interface Calculator : NSObject
{
	double accumulator;
}

// accumulator methods
-(void) setAccumulator: (double) value;
-(void) clear;
-(double) accumulator;

// arithmetic methods
-(double) add: (double) value;
-(double) subtract: (double) value;
-(double) multiply: (double) value;
-(double) divide: (double) value;

-(double) changeSign;  // change accumulator sign
-(double) reciprocal;  // 1/accumulator
-(double) xSquared;    // accumulator squared

@end


@implementation Calculator

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

-(void) clear
{
	accumulator = 0;
}

-(double) accumulator
{
	return accumulator;
}

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

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

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

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

-(double) changeSign
{
	return accumulator = -accumulator;
}

-(double) reciprocal
{
	return accumulator = 1/accumulator;
}

-(double) xSquared
{
	return accumulator *= accumulator;
}

@end


int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
	
    Calculator * deskCalc;
	
	deskCalc = [[Calculator alloc] init];
	
	[deskCalc clear];
	[deskCalc setAccumulator: 100.0];
	NSLog(@"100 + 200 =     %g", [deskCalc add: 200]);
	NSLog(@"Divided by 15 = %g", [deskCalc divide: 15.0]);
	NSLog(@"Subtract 15 =   %g", [deskCalc subtract: 10.0]);
	NSLog(@"Multiply by 5 = %g", [deskCalc multiply: 5]);
	
	NSLog(@"Negated = %g", [deskCalc changeSign]);
	NSLog(@"Reciprocal of = %g", [deskCalc reciprocal]);
	NSLog(@"Squared = %g", [deskCalc xSquared]);
	
	[deskCalc release];
	
    [pool drain];
    return 0;
}

[shawnpk]

My question is not related to the code but rather to how you copy your code in color with the line numbers.  Can you please explain this as I have been trying to do this for quite awhile.  Also, can the code be printed like this also?  Thanks