Exercise 7.1 written by me

[Chuckz]

Not verify still， do not use this code.
I will update the code later soon.

Code: (Objective-C)

//Interface File: Fraction.h

#import <Foundation/Foundation.h>

// Define the Fraction class

@interface Fraction: NSObject

@property int numerator, denominator;

-(void) 				print;
-(void) 				setTo: (int) n over: (int) d;
-(double) 			convertToNum;
-(Fraction *)		add: (Fraction *) f;
-(Fraction *) 	subtract: (Fraction *) f;
-(Fraction *)		multiply: (Fraction *) f;
-(Fraction *)		divide: (Fraction *) f;
-(void) 				reduce;
@end

//Implementation File: Fraction.m
#import "Fraction.h"

@implementation Fraction

@synthesize numerator, denominator;

-(void) print
{
	NSLog (@"%i/%i", numerator, denominator);
}

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

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

// Divide argument from receiver
-(Fraction *) divide: (Fraction *) f;
{
	  // To multiply two fractions:
		// (a/b) / (c/d) = (a*d) / (b*c)
		
		// result will store the result of the addition
		Fraction *result = [[Fraction alloc] init];
		
		result.numerator = numerator * f.denominator;
		result.denominator = denominator * f.numerator;
		
		[self reduce];
		
		return result;
}

// Mulitiply argument from receiver
-(Fraction *) multiply: (Fraction *) f;
{
	  // To multiply two fractions:
		// a/b * c/d = (a*c) / (b*d)
		
		// result will store the result of the addition
		Fraction *result = [[Fraction alloc] init];
		
		result.numerator = numerator * f.numerator;
		result.denominator = denominator * f.denominator;
		
		[self reduce];
		
		return result;
}

// Subtract argument from receiver
-(Fraction *) subtract: (Fraction *) f;
{
	  // To subtract two fractions:
		// a/b - c/d = ((a*d) - (b*c)) / (b*d)
		
		// result will store the result of the addition
		Fraction *result = [[Fraction alloc] init];
		
		result.numerator = numerator * f.denominator - denominator * f.numerator;
		result.denominator = denominator * f.denominator;
		
		[self reduce];
		
		return result;
}

//add a Fraction to the receiver
-(Fraction *) add: (Fraction *) f
{
		// To add two fractions:
		// a/b + c/d = ((a*d) + (b*c)) / (b*d)
		
		// result will store the result of the addition
		Fraction *result = [[Fraction alloc] init];
		
		result.numerator = numerator * f.denominator + denominator * f.numerator;
		result.denominator = denominator * f.denominator;
		
		[self reduce];
		
		return result;
}

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

@end


// Test File main.m
#import "Fraction.h"

int main (int argc, char * argv[])
{
	@autoreleasepool{
		Fraction *aFraction = [[Fraction alloc] init];
		Fraction *bFraction = [[Fraction alloc] init];
		
		Fraction *resultFractionAdd, *resultFractionSub, *resultFractionMul, *resultFractionDiv;
		
		[aFraction setTo: 1 over: 4];// set 1st fraction to 1/4
		[bFraction setTo: 1 over: 2];// set 2nd fraction to 1/2
		
		// Add
		[aFraction print];
		NSLog (@"+");
		[bFraction print];
		NSLog (@"=");
		
		resultFractionAdd = [aFraction add: bFraction];
		[resultFractionAdd print];
		
		// Subtract
		[aFraction print];
		NSLog (@"-");
		[bFraction print];
		NSLog (@"=");
		
		resultFractionSub = [aFraction subtract: bFraction];	
		[resultFractionSub print];
		
		// Multiply
		[aFraction print];
		NSLog (@"*");
		[bFraction print];
		NSLog (@"=");
		resultFractionMul = [aFraction multiply: bFraction];
		[resultFractionMul print];
		
		// Div 
		[aFraction print];
		NSLog (@"/");
		[bFraction print];
		NSLog (@"=");
		resultFractionMul = [aFraction Div: bFraction];
		[resultFractionDiv print];
		
	}
	
	return 0;
}