What is wrong with this Obj-C code?

It's an example program in a textbook. It does not run as expected. It's supposed to simulate a sigma calculation and add all the fractions in a series. but it just gives me 0.000000 when it's done the loop. Any ideas? Thanks in advance:

#import <Foundation/Foundation.h>

// The Fraction class

@interface Fraction : NSObject

{
    int numerator;
    int denominator;
}

@property int numerator, denominator;

-(void) print;
-(void) set: (int) n: (int) d;
-(double) convertToNum;
-(void) reduce;
-(Fraction *) add: (Fraction *) f;


@end

-------------------------------------

#import "Fraction.h"


@implementation Fraction

@synthesize numerator, denominator;

-(void) print

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

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

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


-(void) reduce

{
    int u = numerator;
    int v = denominator;
    int temp;

    while (v != 0) {
        temp = v % u;
        u = v;
        v = temp;
    }

    numerator /= u;
    denominator /= u;
}


-(Fraction *) add: (Fraction *) f

{

    Fraction *result = [[Fraction alloc] init];
    int resultNum, resultDenom;

    resultNum = numerator * f.denominator + 
    denominator * f.nume开发者_运维技巧rator;
    resultDenom = denominator * f.denominator;

    [result set: resultNum: resultDenom];

    [result reduce];
    return result;
}

@end



--------------------------------------------

#import "Fraction.h"

int main (int argc, char *argv[])
{

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; 

    Fraction *aFraction = [[Fraction alloc] init]; 
    Fraction *sum = [[Fraction alloc] init], *sum2; 
    int i, pow2, n;

    // set 1stfraction to 0 

    [sum set: 0.0 : 1.0];



    NSLog (@"Enter your value for n:");
    scanf ("%i", &n);


    pow2 = 2; 
    for (i = 1; i <= n; ++i) {
        [aFraction set: 1 : pow2]; 
        sum2 = [sum add: aFraction]; 
        [sum release]; // release previous sum 
        sum = sum2; 
        pow2 *= 2;


    }

    NSLog (@"After %i iterations, the sum is %f", n, [sum convertToNum]);
    [aFraction release];
    [sum release];




    [pool drain];
    return 0;
}

Your convertToNum method is declared as returning a double, but the actual value you return is an int (the result of dividing two ints is always an int), so in practice any values less than 1 will be truncated to 0.

Also, as a side note: That coding style, where you don't give names to arguments, is really hard to read. - (void)set:(int)n :(int)d is not a good method declaration, and if that's actually used in a book, it should be pulled from print. There's no clue what n and d are, and the second argument doesn't have anything but a colon before it. It should be something like - (void)setNumerator:(int)aNumerator denominator:(int)aDenominator.

Your convertToNum function will return 0 when the numerator is smaller than the denominator. Try changing it to this:

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

Reduce seems incorrect. I don't know how to make that logic work, but

i = 2;
    lLimit = ((lNumerator > lDenominator) ? lNumerator : lDenominator)/2;

while (i < lLimit) {
    if ((lNumerator %  i == 0) &&(lDenominator % i == 0)) {
        lNumerator /= i;
        lDenominator /= i;
        i = 1;
    }
    i++;
}

should be closer. sorry for the name changes, but i don't work too well with lots of single letter vars