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  1. #include <stdio.h>
  2.  
  3. #define INTERFACE(Name) \
  4. template <typename ImplType> \
  5. struct Name
  6.  
  7. #define INTERFACE_FUNC(Ret, Name, Args) \
  8. template <typename... TArgs> \
  9. inline Ret Name (TArgs... args) { \
  10.     static constexpr Ret (ImplType::*ptr) Args = &ImplType::Name; \
  11.     return ((static_cast<ImplType *>(this))->*ptr)(args...); \
  12. }
  13.  
  14. INTERFACE(Iface) {
  15.     INTERFACE_FUNC(int, Foo, (int x, int y))
  16.     INTERFACE_FUNC(void, Bar, (double a))
  17. };
  18.  
  19. struct Impl : Iface<Impl> {
  20.     int Foo (int x, int y)
  21.     {
  22.         return x + y;
  23.     }
  24.  
  25.     void Bar (double a)
  26.     {
  27.         printf("%f\n", a);
  28.     }
  29.  
  30.     void NotExposed ()
  31.     {
  32.     }
  33. };
  34.  
  35. template <typename ImplType>
  36. void UseViaIface (Iface<ImplType> *iface)
  37. {
  38.     int res = iface->Foo(2, 4);
  39.     printf("%d\n", res);
  40.  
  41.     iface->Bar(3.4);
  42.  
  43.     // Compile error because NotExposed is not part of the interface.
  44.     //iface->NotExposed();
  45. }
  46.  
  47. int main ()
  48. {
  49.     Impl impl;
  50.     UseViaIface(&impl);
  51.     return 0;
  52. }
  53.  
  54.  
Success #stdin #stdout 0s 3468KB
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3.400000
https://ideone.com/yPaZ17
language:
C++14 (gcc 8.3)
created:
9 years ago
visibility:
public

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