Error in example 7.6 example in 3rd edition book?

[dharr19]

#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 *sum = [[Fraction alloc] init], *sum2;  << sum2 declared here
    int i, n, pow2;
   
    [sum setTo:0 over:1]; // set first fraction to 0
   
    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]);  << I get the error Assigning from incompatible type void
    [aFraction release];
    [sum release];
   
    [pool drain];
    return 0;
}

[bpedit]

It looks to me like you've entered the code into main properly. Since this program worked for me, I'd say your problem is outside of main. Check your Fraction files and make sure your convertToNumber method is returning a "double" type .