Program 7.6 and Exercise 7.3

[webwrx]

Exercise 7.3 reads -

Modify program 7.7 7.6 to also display the resulting sum as a fraction, not just as a real number.

I'm having some weirdness with this example program, which is carrying through to this exercise.

The example in the book shows you can enter values for 5, 10, and 15 and get the answers 0.96875, 0.999023, 0.999969 respectively.

I'm getting a 0.96875 for 5, but anything 8 and above I'm just getting 1 as the answer.

My convertToNum method as per the book -

Code: (Objective-C)

-(double) convertToNum
{
	if (denominator != 0)
		return (double) numerator / denominator;
	else
		return 1.0;
}

And the relevant section of int main

Code: (Objective-C)

	Fraction *aFraction = [[Fraction alloc] init];
	Fraction *sum = [[Fraction alloc] init], *sum2;
	int i, n, pow2;
	
	[sum setTo: 0 over: 1];
	
	NSLog(@"Enter your value for n:");
	scanf("%i", &n);
	
	pow2 = 2;
	for (i = 1; i <= n; ++i) {
		[aFraction setTo: 1 over: pow2];
		sum2 = [sum add: aFraction];
		[sum release];
		sum = sum2;
		pow2 *= 2;
	}
	
	NSLog (@"After %i iterations, the sum is %g.", n, [sum convertToNum]);
	[aFraction release];
	[sum release];

Once I sort out what's going on with this I'm confident I can answer exercise 7.3 quite easily.

Ben

[skochan]

Ben,

I don't see any problems with your code. Can you post your Fraction.m file?

Cheers,

Steve Kochan

[webwrx]

Fraction.m

Code: (Objective-C)

//
//  Fraction.m
//  exer7-1
//
//  Created by Ben Johnson on 15/09/09.
//  Copyright 2009 __MyCompanyName__. All rights reserved.
//

#import "Fraction.h"

@implementation Fraction
@synthesize numerator, denominator;

-(void) setTo: (int) n over: (int) d
{
	self.numerator = n;
	self.denominator = d;
}

-(void) print
{
	int sign;
	int u;
	int v;

	// test if fraction is positive or negative
	if ((numerator >= 0 && denominator >= 0) || (numerator < 0 && denominator < 0))
		sign = 1;
	else
		sign = -1;
	
	// get absolute value of numerator into temp variable u
	if (numerator < 0)
		u = -numerator;
	else
		u = numerator;
	
	// get absolute value of denominator into temp variable v
	if (denominator < 0)
		v = -denominator;
	else
		v = denominator;
			
	// perform printing operation
	if (numerator == denominator)
		NSLog(@"1");
	else if (numerator == 0)
		NSLog(@"0");
	else if (denominator == 0)
		NSLog(@"Divide by Zero!");
	else if (u < v)
		NSLog(@"%i/%i", sign * u, v);
	else
		NSLog(@"%i %i/%i", sign * u/v, u-v, v);
}

-(void) printReduced: (BOOL) r
{
	if (r == YES) {
		Fraction *tempResult = [[Fraction alloc] init];
		[tempResult setNumerator: numerator];
		[tempResult setDenominator: denominator];
		[tempResult reduce];
		[tempResult print];
		[tempResult release];
	}
	else
		[self print];
}

-(double) convertToNum
{
	if (denominator != 0)
		return (double) numerator / denominator;
	else
		return 1.0;
}

-(void) reduce
{
	int u = numerator;
	int v = denominator;
	int temp;
	
	while (v != 0) {
		temp = u % v;
		u = v;
		v = temp;
	}
	
	numerator /= u;
	denominator /= u;
}

-(Fraction *) add: (Fraction *) f
{
	Fraction *result = [[Fraction alloc] init];
	result.numerator = numerator * f.denominator + denominator * f.numerator;
	result.denominator = denominator * f.denominator;
	return result;
}

-(Fraction *) subtract: (Fraction *) f
{
	Fraction *result = [[Fraction alloc] init];
	result.numerator = numerator * f.denominator - denominator * f.numerator;
	result.denominator = denominator * f.denominator;
	return result;
}

-(Fraction *) multiply: (Fraction *) f
{
	Fraction *result = [[Fraction alloc] init];
	result.numerator = numerator * f.numerator;
	result.denominator = denominator * f.denominator;
	return result;
}

-(Fraction *) divide: (Fraction *) f
{
	Fraction *result = [[Fraction alloc] init];
	result.numerator = numerator * f.denominator;
	result.denominator = denominator * f.numerator;
	return result;
}

@end

[webwrx]

Unrelated - but in case anyone is trying to follow my logic with printing mixed fractions, I just noticed a couple of minor fixes. It now properly handles cases where the whole number is 2 or more. Also previously wasn't handling the possibility where the answer is -1. Have fixed below.

Code: (Objective-C)

	// perform printing operation
	if (numerator == denominator)
		NSLog(@"1");
	else if (numerator == -denominator)
		NSLog(@"-1");
	else if (numerator == 0)
		NSLog(@"0");
	else if (denominator == 0)
		NSLog(@"Divide by Zero!");
	else if (u < v)
		NSLog(@"%i/%i", sign * u, v);
	else
		NSLog(@"%i %i/%i", sign * u/v, u - (u/v) * v, v);