#import <Foundation/NSObject.h>

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

    -(void) print;
    -(void) setNumerator: (int) n;
    -(void) setDenominator: (int) d;
    -(int) numerator;
    -(int) denominator;
    @end

#import "Fraction.h"
    #import <stdio.h>

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

    -(void) setNumerator: (int) n {
        numerator = n;
    }

    -(void) setDenominator: (int) d {
        denominator = d;
    }

    -(int) denominator {
        return denominator;
    }

    -(int) numerator {
        return numerator;
    }
    @end

#import <stdio.h>
    #import "Fraction.h"

    int main( int argc, const char *argv[] ) {
        // create a new instance
        Fraction *frac = [[Fraction alloc] init];

        // set the values
        [frac setNumerator: 1];
        [frac setDenominator: 3];

        // print it
        printf( "The fraction is: " );
        [frac print];
        printf( "n" );

        // free memory
        [frac release];

        return 0;
    }

$ sudo apt-get install gobjc gnustep gnustep-devel
$ gcc `gnustep-config --objc-flags` -o main main.m -lobjc -lgnustep-base
/tmp/ccIQKhfH.o:(.data.rel+0x0): undefined reference to `__objc_class_name_Fraction'

include ${GNUSTEP_MAKEFILES}/common.make


TOOL_NAME = main
main_OBJC_FILES = main.m


include ${GNUSTEP_MAKEFILES}/tool.make

$ source /usr/share/GNUstep/Makefiles/GNUstep.sh
$ make
Making all for tool main...
 Linking tool main ...
./obj/main.o:(.data.rel+0x0): undefined reference to `__objc_class_name_Fraction'

undefined reference to `__objc_class_name_Fraction'

gcc -I /usr/include/GNUstep/ -I /usr/include/mysql -L /usr/lib/GNUstep/
	-lgnustep-base -lmysqlclient
	-g -ggdb
	-fconstant-string-class=NSConstantString -o test *.m

#import <stdio.h>
#import "Fraction.m"

int main( int argc, const char *argv[] ) {
    //create a new instance
    Fraction *frac = [[Fraction alloc] init];

    //set the values
    [frac setNumerator: 1];
    [frac setDenominator: 3];

    //print it
    printf("The fraction is : ");
    [frac print];
    printf("n");

    //free memory
    [frac release];

    return 0;
}