C++模板编程 - 第三章 类模板

 1 #include<iostream>
 2 
 3 using std::cout;
 4 using std::endl;
 5 
 6 // version 1
 7 int max(int a, int b)
 8 {
 9     cout << "int max(int, int) is called." << endl;
10     return a > b ? a : b;
11 }
12 
13 // version 2
14 template<typename T>
15 T max(const T & a, const T & b)
16 {
17     cout << "template<typename T> T max(const T &, const T &) is called." << endl;
18     return a > b ? a : b;
19 }
20 
21 // version 3
22 template<>
23 int max(const int & a, const int & b)
24 {
25     cout << "template<> int max(const int &, const int &)is called." << endl;
26     return a > b ? a : b;
27 }
28 
29 int main()
30 {
31     cout << max(1, 2) << endl;        // version 1 is called
32     cout << max<>(1, 2) << endl;    // version 3 is called
33     cout << max(1.0, 2.0) << endl;    // version 2 is called
34     return 0;
35 }

 1 #include<iostream>
 2 
 3 using std::cout;
 4 using std::endl;
 5 
 6 // version 0
 7 template<typename T1, typename T2> class SomeClass
 8 {
 9 public:
10     SomeClass()
11     {
12         cout << "version 0" << endl;
13     }
14 };
15 
16 // version 1
17 template<typename T> class SomeClass < T, T >
18 {
19 public:
20     SomeClass()
21     {
22         cout << "version 1" << endl;
23     }
24 };
25 
26 // version 2
27 template<typename T> class SomeClass < T, int >
28 {
29 public:
30     SomeClass()
31     {
32         cout << "version 2" << endl;
33     }
34 };
35 
36 // version 3
37 template<typename T1, typename T2> class SomeClass < T1*, T2* >
38 {
39 public:
40     SomeClass()
41     {
42         cout << "version 3" << endl;
43     }
44 };
45 
46 // version 4
47 template<typename T> class SomeClass < T*, T* > 
48 {
49 public:
50     SomeClass()
51     {
52         cout << "version 4" << endl;
53     }
54 };
55 
56 
57 int main()
58 {
59 //    SomeClass<int, int> FirstClass;       // Oooooops! This one matches BOTH 2 and 3 -- CONFUSING
60     SomeClass<float*, int*> SecondClass;    // version 3
61     SomeClass<int*, int*> ThirdClass;       // version 4 -- WITHOUT version 4, this is an error! -- CONFUSING
62     SomeClass<int, char> ForthClass;        // version 0
63     SomeClass<char, int> FifthClass;        // version 2
64     SomeClass<double, double> FixthClass;   // version 1
65 }