Program 11.1 MathOps Category and Test Program

[esc]

Program 11.1 (main.m)

Code: (Objective-C)

#import "Fraction.h"

@interface Fraction (MathOps)
-(Fraction *) add: (Fraction *) f;
-(Fraction *) mul: (Fraction *) f;
-(Fraction *) sub: (Fraction *) f;
-(Fraction *) div: (Fraction *) f;
@end

@implementation Fraction (MathOps)
-(Fraction *) add: (Fraction *) f
{
	// To add two fractions:
	// a/b + c/d = ((a*d) + (b*c) / (b * d)
	
	Fraction *result = [[Fraction alloc] init];
	int resultNum, resultDenom;
	
	resultNum = (numerator * f.denominator) + (denominator * f.numerator);
	resultDenom = denominator * f.denominator;
	
	[result setTo: resultNum over: resultDenom];
	[result reduce];
	
	return result;
}

-(Fraction *) sub: (Fraction *) f
{
	// To sub two fractions:
	// a/b - c/d = ((a*d) - (b*c)) / (b * d)
	
	Fraction *result = [[Fraction alloc] init];
	int resultNum, resultDenom;
	
	resultNum = (numerator * f.denominator) - (denominator * f.numerator);
	resultDenom = denominator * f.denominator;
	
	[result setTo: resultNum over: resultDenom];
	[result reduce];
	
	return result;
}

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

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

@end


int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

	Fraction *a = [[Fraction alloc] init];
	Fraction *b = [[Fraction alloc] init];
	Fraction *result;
	
	[a setTo: 1 over: 3];
	[b setTo: 2 over: 5];
	
	[a print];  NSLog (@"  +");  [b print];  NSLog (@"-----");
	result = [a add: b];
	[result print];
	NSLog (@"\n");
	[result release];
	
	[a print];  NSLog (@"  -");  [b print];  NSLog (@"-----");
	result = [a sub: b];
	[result print];
	NSLog (@"\n");
	[result release];
	
	[a print];  NSLog (@"  *");  [b print];  NSLog (@"-----");
	result = [a mul: b];
	[result print];
	NSLog (@"\n");
	[result release];
	
	[a print];  NSLog (@"  /");  [b print];  NSLog (@"-----");
	result = [a div: b];
	[result print];
	NSLog (@"\n");
	[result release];
	[a release];
	[b release];
    
    [pool drain];
    return 0;
}

Fraction.h

Code: (Objective-C)

#import <Foundation/Foundation.h>
#import <stdio.h>

// Define the Fraction class

@interface Fraction : NSObject {
	int numerator;
	int denominator;
}

@property int numerator, denominator;
-(void) setTo: (int) n over: (int) d;
-(void) reduce;
-(double) convertToNum;
-(void) print;

@end

Fraction.m

Code: (Objective-C)

#import "Fraction.h"

@implementation Fraction

@synthesize numerator, denominator;

-(void) print
{
	if ( denominator < 0 )
		NSLog (@"-%i/%i", numerator, -denominator);
	else
		NSLog (@"%i/%i", numerator, denominator);
}

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

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

-(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

[Goose]

Program 11.1 (main.m)

Code: (Objective-C)

#import "Fraction.h"

@interface Fraction (MathOps)
-(Fraction *) add: (Fraction *) f;
-(Fraction *) mul: (Fraction *) f;
-(Fraction *) sub: (Fraction *) f;
-(Fraction *) div: (Fraction *) f;
@end

@implementation Fraction (MathOps)
-(Fraction *) add: (Fraction *) f
{
	// To add two fractions:
	// a/b + c/d = ((a*d) + (b*c) / (b * d)
	
	Fraction *result = [[Fraction alloc] init];
	int resultNum, resultDenom;
	
	resultNum = (numerator * f.denominator) + (denominator * f.numerator);
	resultDenom = denominator * f.denominator;
	
	[result setTo: resultNum over: resultDenom];
	[result reduce];
	
	return result;
}

-(Fraction *) sub: (Fraction *) f
{
	// To sub two fractions:
	// a/b - c/d = ((a*d) - (b*c)) / (b * d)
	
	Fraction *result = [[Fraction alloc] init];
	int resultNum, resultDenom;
	
	resultNum = (numerator * f.denominator) - (denominator * f.numerator);
	resultDenom = denominator * f.denominator;
	
	[result setTo: resultNum over: resultDenom];
	[result reduce];
	
	return result;
}

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

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

@end

Why would you put this in the main.m section vs. Fraction.m or Fraction.h?  It just seem out of place there.  What is the best way to organize categories within your program?

[skochan]

You can put the category in separate .h and .m files, much like adding a new class.  For example, you might put the category definition into files called FractionMathOps.h and FractionMathops.m and then import FractionMathOps.h into any file that wants to use the methods defined in the category (such as main.m).

Cheers,

Steve Kochan

[Goose]

Thanks