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?
 1 //--------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----------
 2 - (void) print: (BOOL) yesOrNo//打印
 3 {
 4     if (yesOrNo == YES) {
 5         [self reduce];
 6     }
 7     
 8     if (num < 0)
 9     {
10         num = -num;
11         NSLog(@"-%i/%i",num,den);
12     }
13     else
14     {
15         NSLog(@"%i/%i",num,den);
16     }
17 }
18 
19 - (Fraction *) subFraction: (Fraction *) f
20 {
21     Fraction *result = [[Fraction alloc]init];
22     
23     result.num = num * f.den - den * f.num;
24     result.den = den * f.den;
25     
26     //[result reduce];
27     
28     return result;
29     
30 }
31 
32 
33 #import <Foundation/Foundation.h>
34 #import "Fraction.h"
35 
36 int main(int argc, const char * argv[]) {
37     @autoreleasepool {
38         Fraction *myF = [[Fraction alloc]init];
39         Fraction *myF_2 = [[Fraction alloc]init];
40         Fraction *myResult;
41         
42         int i;//接受输入1或0
43         BOOL b;//布尔类型判断i的值
44         
45         [myF setN:1 andSetD:4];
46         [myF_2 setN:1 andSetD:2];
47         
48         NSLog(@"Need to Simple? 1 or 0");//提示输入1或0
49         scanf("%i",&i);
50         b = i;//将i值传给布尔类型的b判断是否对分数进行约简
51         
52         myResult = [myF subFraction:myF_2];//减法
53         [myResult print:b];
54         
55         myResult = [myF mulFraction:myF_2];//乘法
56         //[myResult print];
57         
58         myResult = [myF divFraction:myF_2];//除法
59         [myResult print:b];
60         
61         //[myResult print];
62         
63         
64     }
65     return 0;
66 }