C++primer 14.2.1节练习

练习14.6

 1 #include <iostream>
 2 #include <string>
 3 #include <memory>
 4 #include <vector>
 5 #include <algorithm>
 6 #include <numeric>
 7
 8 using namespace std;
 9
10 class Sales_data {
11     friend istream& operator >> (istream& is, Sales_data &s);
12     friend ostream& operator<<(ostream& os, Sales_data s);
13 public:
14     Sales_data() : bookNo("") {}
15     Sales_data(string s, unsigned us, double up) : bookNo(s), units_sold(us), units_price(up) {}
16     Sales_data operator+(const Sales_data& s);
17     Sales_data& operator+=(const Sales_data& s);
18 private:
19     string bookNo;
20     unsigned units_sold = 0;
21     double units_price = 0;
22 };
23
24 istream& operator >> (istream& is, Sales_data &s);
25 ostream& operator<<(ostream& os, Sales_data s);
26
27 int main()
28 {
29     Sales_data s1;
30     Sales_data s2("C++ primer", 10, 128.2);
31     cout << s2 << endl;
32     s1 = s2;
33     cout << s1 << endl;
34     cout << s1 + s2 << endl;
35     s1 += s2;
36     cout << s1 << endl;
37     cin >> s1;
38     cout << s1;
39     cout << s1 + s2 << endl;
40     system("pause");
41     return 0;
42 }
43
44 istream & operator >> (istream & is, Sales_data &s)
45 {
46     is >> s.bookNo >> s.units_sold >> s.units_price;
47     return is;
48     // TODO: 在此处插入 return 语句
49 }
50
51 ostream & operator<<(ostream & os, Sales_data s)
52 {
53     os << s.bookNo << " " << s.units_sold << " " << s.units_price;
54     return os;
55     // TODO: 在此处插入 return 语句
56 }
57
58 Sales_data & Sales_data::operator+=(const Sales_data & s)
59 {
60     if (bookNo == s.bookNo)
61     {
62         units_sold = units_sold + s.units_sold;
63         return *this;
64     }
65     else
66     {
67         cout << "can not add" << endl;
68         return *this;
69     }
70     // TODO: 在此处插入 return 语句
71 }
72
73 Sales_data Sales_data::operator+(const Sales_data & s)
74 {
75     if (bookNo == s.bookNo)
76     {
77         Sales_data ss;
78         ss.bookNo = bookNo;
79         ss.units_price = units_price;
80         ss.units_sold = units_sold + s.units_sold;
81         return ss;
82     }
83     else
84     {
85         cout << "error" << endl;
86         return *this;
87     }
88     // TODO: 在此处插入 return 语句
89 }

练习14.7

 1 #include <iostream>
 2 #include <string>
 3 #include <utility>
 4 #include <memory>
 5 #include <algorithm>
 6
 7 using namespace std;
 8
 9 class String {
10     friend ostream &operator<<(ostream &os, String &s);
11 public:
12     String() : element(nullptr), first_free(nullptr) {}
13     String(char *);
14 private:
15     static allocator<char> alloc;
16     char *element;
17     char *first_free;
18 };
19 allocator<char> String::alloc;
20 ostream &operator<<(ostream &os, String &s);
21
22 int main()
23 {
24     String s1;
25     String s2("hello");
26     String s3("hello world");
27     cout << s1;
28     cout << s2;
29     cout << s3;
30     system("pause");
31     return 0;
32 }
33
34 String::String(char *s)
35 {
36     int i = 0;
37     while (s[i] != ‘\0‘)
38         ++i;
39     auto newloc = alloc.allocate(i);
40     auto dest = newloc;
41     for (auto count = 0; count != i;++count)
42         alloc.construct(dest++, s[count]);
43     element = newloc;
44     first_free = dest;
45 }
46
47 ostream & operator<<(ostream &os, String &s)
48 {
49     while (s.element != s.first_free)
50     {
51         os << *(s.element);
52         s.element++;
53     }
54     cout << endl;
55     return os;
56     // TODO: 在此处插入 return 语句
57 }

练习14.8

类似上题，很简单，细心注意一下就行了