objective-c第七章课后练习3

题：Fraction类对负分数适用吗？例如：1/4-1/2 能否显示成-1/4?

 //--------类定义实现参考上篇随笔,此处需更改print方法和main主方法部分----------
 - (void) print: (BOOL) yesOrNo//打印
 {
     if (yesOrNo == YES) {
         [self reduce];
     }

     if (num < )
     {
         num = -num;
         NSLog(@"-%i/%i",num,den);
     }
     else
     {
         NSLog(@"%i/%i",num,den);
     }
 }

 - (Fraction *) subFraction: (Fraction *) f
 {
     Fraction *result = [[Fraction alloc]init];

     result.num = num * f.den - den * f.num;
     result.den = den * f.den;

     //[result reduce];

     return result;

 }

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

 int main(int argc, const char * argv[]) {
     @autoreleasepool {
         Fraction *myF = [[Fraction alloc]init];
         Fraction *myF_2 = [[Fraction alloc]init];
         Fraction *myResult;

         int i;//接受输入1或0
         BOOL b;//布尔类型判断i的值

         [myF setN: andSetD:];
         [myF_2 setN: andSetD:];

         NSLog(@"Need to Simple? 1 or 0");//提示输入1或0
         scanf("%i",&i);
         b = i;//将i值传给布尔类型的b判断是否对分数进行约简

         myResult = [myF subFraction:myF_2];//减法
         [myResult print:b];

         myResult = [myF mulFraction:myF_2];//乘法
         //[myResult print];

         myResult = [myF divFraction:myF_2];//除法
         [myResult print:b];

         //[myResult print];

     }
     return ;
 }