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  1. #include <iostream>
  2. #include <cstdio>
  3.  
  4. //lets define few policy classes
  5. struct cout_print_policy
  6. {
  7.     template<typename T>
  8.     static void print(T const & data)
  9.     {
  10.        std::cout << "printing using cout = " << data << std::endl;
  11.     }
  12. };
  13.  
  14. struct printf_print_policy
  15. {
  16.     static void print(int data)
  17.     {
  18.        std::printf("printing int using printf = %d\n", data);
  19.     }
  20.     static void print(double data)
  21.     {
  22.        std::printf("printing double using printf = %f\n", data);
  23.     }
  24. };
  25.  
  26. //now define the class template (called host class) that 
  27. //accepts policy as template argument
  28. template<typename T, typename TPrintPolicy>
  29. class host
  30. {
  31.     typedef TPrintPolicy print_policy;
  32.     T data;
  33.  public:
  34.     host(T const & d) : data(d) {}
  35.     void print() 
  36.     {
  37.         print_policy::print(data);
  38.     }
  39. };
  40.  
  41. //test code
  42. int main()
  43. {
  44.   host<int, cout_print_policy>      ic(100);
  45.   host<double, cout_print_policy>   dc(100.0);
  46.  
  47.   host<int, printf_print_policy>    ip(100);
  48.   host<double, printf_print_policy> dp(100.0);
  49.  
  50.   ic.print();
  51.   dc.print();
  52.   ip.print();
  53.   dp.print();
  54. }
  55.  
  56.  
Success #stdin #stdout 0.02s 2724KB
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stdin
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Standard input is empty
stdout
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printing using cout = 100
printing using cout = 100
printing int using printf = 100
printing double using printf = 100.000000
https://ideone.com/r4Zk4
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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