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  1. #include<type_traits>
  2.  
  3. class foo {
  4. };
  5.  
  6. class bar {
  7. public:
  8. /*
  9.   const foo & to_foo() const {
  10.     return f;
  11.   }
  12. */
  13.   foo & to_foo() {
  14.     return f;
  15.   }
  16. private:
  17.  foo f;
  18. };
  19.  
  20. template< typename T, typename Enable = void >
  21. class convert {};
  22.  
  23. template< typename T >
  24. struct convert< T, typename std::enable_if< std::is_member_function_pointer< decltype( &T::to_foo ) >::value >::type > {
  25.   static const foo & call1( const bar & b ) {
  26.     return b.to_foo();
  27.   }
  28.  
  29.   static foo & call2( bar & b ) {
  30.     return b.to_foo();
  31.   }
  32. };
  33.  
  34. int main() {
  35.   bar b;
  36.   foo & f = convert<bar>::call2( b );
  37.   return 0;
  38. }
Success #stdin #stdout 0s 2824KB
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https://ideone.com/iBKoN
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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