About Program 7.5

[willc2]

I notice the filename is "main.m"

Do I rename "FractionTest.m" from Program 7.4 then edit or do I create a brand new file.

If I create a new file, won't both "main.m" and "FractionTest.m" both execute at runtime?

[skochan]

The filename is not important.  Execution will begin wherever main is located, whether it's in a file called FractionTest.m or main.m.  What you can't have are two functions called main.

Cheers,

Steve

[willc2]

For the purposes of using this book I have found that a student should just edit the 7.4 version of the file "FractionTest.m"

Don't create a new file named "main.m" to match the subhead titled Program 7.5 Test File main.m

[skochan]

Good advice!   

Steve

[i-ash]

For some reason I can't run this example, and I can't figure out why... 

It has an issue with the 'reduce' method, with the debugger highlighting the "numerator /= u;" line.

In the console I get:

[Session started at 2009-03-09 11:36:06 +1100.]
2009-03-09 11:36:06.397 FractionTest[1287:10b] 1/4
2009-03-09 11:36:06.398 FractionTest[1287:10b] +
2009-03-09 11:36:06.399 FractionTest[1287:10b] 1/2
2009-03-09 11:36:06.400 FractionTest[1287:10b] =

[Session started at 2009-03-09 11:36:06 +1100.]
Loading program into debugger…
GNU gdb 6.3.50-20050815 (Apple version gdb-962) (Sat Jul 26 08:14:40 UTC 2008)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-apple-darwin".Program loaded.
sharedlibrary apply-load-rules all
Attaching to program: `/Users/ash/Documents/Education/Obj-C Progs/FractionTest/build/Debug/FractionTest', process 1287.
Current language:  auto; currently objective-c
(gdb)

Can someone please help me?

My code is:

Code: (Objective-C)

//  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 1.0;
}

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

- (Fraction *) add: (Fraction *) f
{
	Fraction *result = [[Fraction alloc] init];
	int resultNum, resultDenom;
	
	resultNum = numerator * f.denominator + denominator * f.numerator;
	resultDenom = denominator * f.denominator;
	[result 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

Code: (Objective-C)

// FractionTest.m

#import <Foundation/Foundation.h>
#import "Fraction.h"

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

	Fraction *aFraction = [[Fraction alloc] init];
	Fraction *bFraction = [[Fraction alloc] init];
	
	Fraction *resultFraction;
	
	// Set two fractions to 1/4 and 1/2 and add them together.
	
	[aFraction setTo: 1 over: 4];
	[bFraction setTo: 1 over: 2];
	
	// Print the results
	
	[aFraction print];
	NSLog(@"+");
	[bFraction print];
	NSLog(@"=");
	
	resultFraction = [aFraction add: bFraction];
	[resultFraction print];
	
	[[aFraction add: bFraction] print];
	
	[aFraction release];
	[bFraction release];
	[resultFraction release];
	
    [pool drain];
    return 0;
}

[skochan]

You're not setting the numerator or denominator in your result fraction inside your add: method.

Cheers,

Steve Kochan

[willc2]

gaahh! Beat me by 30 sec.
 

[skochan]

No, look at the post times....it's more like 8 minutes.   

[i-ash]

Thanks Steve.

I'm starting to struggle with the book a little, in particular the mathematics involved with the algorithms & some key OO concepts... 

[skochan]

Well, we're here to help!

Cheers,

Steve

[kaha]

im having a problem. when i run the code it tells me ..'may not repond to add...


#import "Fraction.h"

int main (int argc, char *argv[])
{
   NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
   
   Fraction *aFraction = [[Fraction alloc] init];
   Fraction *bFraction = [[Fraction alloc] init];
   
   Fraction *resultFraction;
   
   [aFraction setTo: 1 over: 4];   // set 1st fraction to 1/4
   [bFraction setTo: 1 over: 2];   // set 2nd fraction to 1/2
   
   [aFraction print];
   NSLog (@"+");
   [bFraction print];
   NSLog (@"=");
   
   resultFraction = [aFraction add: bFraction];
   [resultFraction print];
   
   // This time give the result directly to print
   // memory leakage here!
   
   [[aFraction add: bFraction] print];
   [aFraction release];
   [bFraction release];
   [resultFraction release];
   
   [pool drain];
   return 0;
}




thanks for any help.

[skochan]

The message typically indicates that the compiler can't find the indicated method defined in the class that uses the method.  Check your Fraction.h and Fraction.m files for the add: method.  Post those files here if you can't isolate the problem.

Cheers,

Steve Kochan

[kaha]

still cant isolate the problem... here is codesl

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

// Define the Fraction class



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

@property int numerator, denominator;

-(void)      print;
-(void)      setTo: (int) n over: (int) d;
-(double)   convertToNum;
@end


Fraction.m... which now also does not respond to reduce

#import "Fraction.h"


@implementation Fraction
// add a Fraction to the reciever

-(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];
   int      resultNum, resultDenom;
   
   resultNum = numerator * f.denominator +
      denominator * f.numerator;
   resultDenom = denominator * f.denominator;
   [result setTo: resultNum over: resultDenom];
   [result reduce];
   
   return result;
   
}

@synthesize numerator, denominator;

-(void) print
{
   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;
}
@end


Thanks again so much

[skochan]

You need to declare the add: method in the interface section for your Fraction class.

Cheers,

Steve Kochan

[kaha]

I DID STILL NADA... is it correct?

#import <Foundation/Foundation.h>

// Define the Fraction class

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

@property int numerator, denominator;

-(void)         print;
-(double)      convertToNum;
-(Fraction *)   add: (Fraction *) f;
-(void)         reduce;
@end