fork download
copy 
  1. #include <type_traits>
  2. #include <utility>
  3. #include <iostream>
  4.  
  5.  
  6.     template <typename...>
  7.     using void_t = void;
  8.  
  9.     template <typename T, template <typename> class D, typename = void>
  10.     struct detect : std::false_type {};
  11.  
  12.     template <typename T, template <typename> class D>
  13.     struct detect<T, D, void_t<D<T>>> : std::true_type {};
  14.  
  15.     template <typename T>
  16.     using has_m = decltype(std::declval<T>().m());
  17.  
  18.  
  19.     template<typename T>
  20.     struct Derived : public T
  21.     {
  22.          void m(std::true_type) { T::m(); }
  23.          void m(std::false_type) {  std::cout<<"Derived\n"; }
  24.          void m() { return m(detect<T, has_m>{}); }
  25.     };
  26.  
  27. struct Base0 { };
  28. struct Base1 { void m() { std::cout<<"Base1\n"; } };
  29.  
  30. int main(){
  31.   Derived<Base0> d0;
  32.   d0.m(); //should print "Derived"
  33.   Derived<Base1> d1;
  34.   d1.m(); //should print "Base1"
  35. }
Success #stdin #stdout 0s 3460KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Derived
Base1
https://ideone.com/z3Jii6
language:
C++14 (gcc 8.3)
created:
8 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!