C++primer 15.2.2节练习

练习15.4

a）错误，一个类不能派生它本身

b）正确，Derived从他的基类Base派生，且规定派生类从基类继承的数据成员对于派生类的用户是不可见。

c）错误，派生类的声明与其他类相差不大，声明中包含类名但是不包含他的派生列表；

练习15.5

 1 #include <iostream>
 2 #include <string>
 3 #include <utility>
 4 #include <memory>
 5 #include <vector>
 6
 7 using namespace std;
 8
 9 class Quote {
10 public:
11     Quote() = default;
12     Quote(const string &book, double sales_price) : bookNo(book), price(sales_price) {}
13     string isbn() { return bookNo; }
14     virtual double net_price(size_t n) const{ return n * price; }
15     virtual ~Quote() = default;
16 private:
17     string bookNo;
18 protected:
19     double price = 0.0;
20 };
21
22 class Bulk_quote : public Quote {
23 public:
24     Bulk_quote() = default;
25     Bulk_quote(const string& book, double p, size_t qty, double disc) : Quote(book, p), min_qty(qty), discount(disc) {}
26     double net_price(size_t n) const;
27 private:
28     size_t min_qty = 0;
29     double discount = 0.0;
30 };
31
32 double print_total(ostream& os, const Quote& item, size_t t);
33
34 int main()
35 {
36
37     system("pause");
38     return 0;
39 }
40
41 double print_total(ostream & os, const Quote &item, size_t t)
42 {
43     double ret = item.net_price(t);
44     os << "ISBN: " << item.isbn << " # sold: " << t << " total due: " << ret << endl;
45     return ret;
46 }
47
48 double Bulk_quote::net_price(size_t n) const
49 {
50     if (n >= min_qty)
51         return n * (1 - discount) * price;
52     else
53         return n * price;
54 }

练习15.6

 1 #include <iostream>
 2 #include <string>
 3 #include <utility>
 4 #include <memory>
 5 #include <vector>
 6
 7 using namespace std;
 8
 9 class Quote {
10 public:
11     Quote() = default;
12     Quote(const string &book, double sales_price) : bookNo(book), price(sales_price) {}
13     const string& isbn() const { return bookNo; }
14     virtual double net_price(size_t n) const{ return n * price; }
15     virtual ~Quote() = default;
16 private:
17     string bookNo;
18 protected:
19     double price = 0.0;
20 };
21
22 class Bulk_quote : public Quote {
23 public:
24     Bulk_quote() = default;
25     Bulk_quote(const string& book, double p, size_t qty, double disc) : Quote(book, p), min_qty(qty), discount(disc) {}
26     double net_price(size_t n) const;
27 private:
28     size_t min_qty = 0;
29     double discount = 0.0;
30 };
31
32 double print_total(ostream& os, const Quote& item, size_t t);
33
34 int main()
35 {
36     Quote q1;
37     Quote q2("C++ primer", 128.00);
38     Bulk_quote b1;
39     Bulk_quote b2("C++ primer", 128.00, 5, 0.4);
40     print_total(cout, q1, 6);
41     print_total(cout, q2, 6);
42     print_total(cout, b1, 6);
43     print_total(cout, b2, 6);
44     system("pause");
45     return 0;
46 }
47
48 double print_total(ostream & os, const Quote &item, size_t t)
49 {
50     double ret = item.net_price(t);
51     os << "ISBN: " << item.isbn() << " # sold: " << t << " total due: " << ret << endl;
52     return ret;
53 }
54
55 double Bulk_quote::net_price(size_t n) const
56 {
57     if (n >= min_qty)
58         return n * (1 - discount) * price;
59     else
60         return n * price;
61 }

练习15.7

 1 #include <iostream>
 2 #include <string>
 3 #include <utility>
 4 #include <memory>
 5 #include <vector>
 6
 7 using namespace std;
 8
 9 class Quote {
10 public:
11     Quote() = default;
12     Quote(const string &book, double sales_price) : bookNo(book), price(sales_price) {}
13     const string& isbn() const { return bookNo; }
14     virtual double net_price(size_t n) const{ return n * price; }
15     virtual ~Quote() = default;
16 private:
17     string bookNo;
18 protected:
19     double price = 0.0;
20 };
21
22 class Bulk_quote : public Quote {
23 public:
24     Bulk_quote() = default;
25     Bulk_quote(const string& book, double p, size_t qty, double disc) : Quote(book, p), min_qty(qty), discount(disc) {}
26     double net_price(size_t n) const;
27 private:
28     size_t min_qty = 0;
29     double discount = 0.0;
30 };
31
32 class lim_discount : public Quote {
33 public:
34     lim_discount() = default;
35     lim_discount(const string& book, double p, size_t lcount, double ldis) : Quote(book, p), lim_count(lcount), lim_dis(ldis) {}
36     double net_price(size_t n) const override;
37 private:
38     size_t lim_count = 0;
39     double lim_dis = 0.0;
40 };
41 double print_total(ostream& os, const Quote& item, size_t t);
42
43 int main()
44 {
45     Quote q1;
46     Quote q2("C++ primer", 128.00);
47     Bulk_quote b1;
48     Bulk_quote b2("C++ primer", 128.00, 5, 0.4);
49     print_total(cout, q1, 6);
50     print_total(cout, q2, 6);
51     print_total(cout, b1, 6);
52     print_total(cout, b2, 6);
53     lim_discount l1("C++ primer", 128.00, 10, 0.5);
54     print_total(cout, l1, 9);
55     print_total(cout, l1, 11);
56     system("pause");
57     return 0;
58 }
59
60 double print_total(ostream & os, const Quote &item, size_t t)
61 {
62     double ret = item.net_price(t);
63     os << "ISBN: " << item.isbn() << " # sold: " << t << " total due: " << ret << endl;
64     return ret;
65 }
66
67 double Bulk_quote::net_price(size_t n) const
68 {
69     if (n >= min_qty)
70         return n * (1 - discount) * price;
71     else
72         return n * price;
73 }
74
75 double lim_discount::net_price(size_t n) const
76 {
77     if (n <= lim_count)
78         return n * (1 - lim_dis) * price;
79     else
80         return Quote::net_price(n);
81 }