fork download
copy 
  1. #include<iostream>
  2. class HasFoo
  3. {
  4.     public :
  5.  
  6.     typedef char (&Small)[1];
  7.     typedef char (&Large)[2];
  8.  
  9.     template <typename C, void (C::*) ()> class SFINAE {}; 
  10.  
  11.     template <typename C> static Small test (SFINAE<C, &C::foo> *)
  12.     {   
  13.         std::cout << "HAS" << std::endl;
  14.     }   
  15.  
  16.     template <typename C> static Large test (...)
  17.     {   
  18.         std::cout << "NOT HAS" << std::endl;
  19.     }   
  20. };
  21.  
  22. class B
  23. {
  24.     public :
  25.  
  26.     void foo () {}
  27. };
  28.  
  29. class D1 : public B
  30. {
  31.   private: void foo () {} // override
  32. };
  33.  
  34. class D2 : public B
  35. {
  36.     public :
  37.  
  38.     using B::foo;
  39. };
  40.  
  41. class D3 : public B {}; 
  42.  
  43. /////////////////////////////////////////////////////////////////
  44.  
  45. template<typename C, void (C::*p)()>
  46. struct X{};
  47.  
  48. template struct X<D1,&D1::foo>;  //<--- private members can be used in explicit instantiation
  49.  
  50. //////////////////////////////////////////////////////////////////
  51.  
  52. int main ()
  53. {
  54.   //  HasFoo::test<B>(0);
  55.   //  HasFoo::test<D1>(0);
  56.   //  HasFoo::test<D2>(0);
  57.   //  HasFoo::test<D3>(0);
  58. }
Success #stdin #stdout 0.02s 2676KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Standard output is empty
https://ideone.com/qIdVN
language:
C++ (gcc 8.3)
created:
11 years ago
visibility:
public

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!