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  1. #include <iostream>
  2.  
  3. struct low_priority {};
  4. struct high_priority : low_priority {};
  5. struct highest_priority : high_priority {};
  6.  
  7. template<typename T>
  8. class Mixin
  9. {
  10. private:
  11.  
  12.     template<typename T2>
  13.     static auto CallImpl( highest_priority const& ) -> decltype( T2::SomeFunc(), void() )
  14.     {
  15.     	std::cout << "1\n";
  16.         T::SomeFunc();
  17.     }
  18.  
  19.     template<typename T2>
  20.     static auto CallImpl( high_priority const& ) -> decltype( T2{}.SomeFunc(), void() )
  21.     {
  22.     	std::cout << "2\n";
  23.         T{}.SomeFunc();
  24.     }
  25.  
  26.     template<typename T2>
  27.     void CallImpl( low_priority const& )
  28.     {
  29.     	std::cout << "3\n";
  30.         DefaultImpl();
  31.     }
  32.  
  33. public:
  34.  
  35.     void Call()
  36.     {
  37.         CallImpl<T>(highest_priority{});
  38.     }
  39.  
  40.    void DefaultImpl()
  41.    {
  42.         std::cout << "Mixin::DefaultImpl\n";
  43.    }
  44. };
  45.  
  46. struct A
  47. {
  48.    static void SomeFunc()
  49.    {
  50.         std::cout << "A::SomeFunc()\n";
  51.    }
  52. };
  53.  
  54. struct C
  55. {
  56.    void SomeFunc()
  57.    {
  58.         std::cout << "C::SomeFunc()\n";
  59.    }
  60. };
  61.  
  62. struct B {};
  63.  
  64. int main()
  65. {
  66.     Mixin<A>{}.Call();
  67.     Mixin<B>{}.Call();
  68.     Mixin<C>{}.Call();
  69. }
  70.  
Success #stdin #stdout 0s 3296KB
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Standard input is empty
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1
A::SomeFunc()
3
Mixin::DefaultImpl
2
C::SomeFunc()
https://ideone.com/BjorWN
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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