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  1. #include <assert.h>         // assert
  2. #include <string>           // std::string
  3. using namespace std;
  4.  
  5. struct Person
  6. {
  7.     string  name;
  8.  
  9.     bool isEqualTo( Person const& other ) const
  10.     {
  11.         return (name == other.name);
  12.     }
  13.  
  14.     Person( string const& _name )
  15.         : name( _name )
  16.     {}
  17. };
  18.  
  19. bool operator==( Person const& a, Person const& b )
  20. { return a.Person::isEqualTo( b ); }
  21.  
  22. struct Student
  23.     : Person
  24. {
  25.     int     studentId;
  26.  
  27.     bool isEqualTo( Student const& other ) const
  28.     {
  29.         return (Person::isEqualTo( other ) && studentId == other.studentId);
  30.     }
  31.  
  32.     Student( string const& _name, int const _studentId )
  33.         : Person( _name ), studentId( _studentId )
  34.     {}
  35. };
  36.  
  37. bool operator==( Student const& a, Student const& b )
  38. { return a.Student::isEqualTo( b ); }
  39.  
  40. int main()
  41. {
  42.     Person  a( "Hillary Clinton" );
  43.     Student b( "John Smith", 12345 );
  44.  
  45.     a = b;              // I once expected this assignment to NOT COMPILE!
  46.     // Here there is no `a.studentId`. The Student value has been SLICED.
  47.  
  48.     assert( a == b );   // The Person class' isEqualTo still says "equal".
  49. }
  50.  
Success #stdin #stdout 0.02s 2852KB
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https://ideone.com/TgZKn
language:
C++ (gcc 8.3)
created:
14 years ago
visibility:
public

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