有趣的C++模板代码

 1 #include <iostream>
 2 template <typename ... Ts>
 3 struct CNAny {
 4     static bool Do(int i) {
 5         return (Ts::Do(i) || ...);
 6     }
 7 };
 8 
 9 template <typename ... Ts>
10 struct CNAll {
11     static bool Do(int i) {
12         return (Ts::Do(i) && ...);
13     }
14 };
15 
16 struct CNa {
17     static bool Do(int i) {
18         return i > 5;
19     }
20 };
21 
22 struct CNb {
23     static bool Do(int i) {
24         return i < 10;
25     }
26 };
27 
28 #define TEST(e) do {\
29     bool yes = (e); \
30     std::cout << #e << " = " << yes << std::endl; \
31 } while (0)
32 
33 int main() {
34     using CNAny_CNa_CNb = CNAny<CNa, CNb>;
35     TEST( CNAny_CNa_CNb::Do(1)  );
36     TEST( CNAny_CNa_CNb::Do(7)  );
37     TEST( CNAny_CNa_CNb::Do(12) );
38     
39     using CNAll_CNa_CNb = CNAll<CNa, CNb>;
40     TEST( CNAll_CNa_CNb::Do(1)  );
41     TEST( CNAll_CNa_CNb::Do(7)  );
42     TEST( CNAll_CNa_CNb::Do(12) );
43     
44     return 0;
45 }

输出内容：

CNAny_CNa_CNb::Do(1) = 1
CNAny_CNa_CNb::Do(7) = 1
CNAny_CNa_CNb::Do(12) = 1
CNAll_CNa_CNb::Do(1) = 0
CNAll_CNa_CNb::Do(7) = 1
CNAll_CNa_CNb::Do(12) = 0