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  1. #include <cstdio>
  2. #include <memory>
  3.  
  4. class B {
  5. private:
  6.   virtual B *clone_impl( ){ return new B( *this ); }
  7. protected:
  8.   int b;
  9. public:
  10.   explicit B( int x ): b( x ){ }
  11.   B( const B &that ): b( that.b ){ }
  12.   virtual ~B( ){ }
  13.   std::shared_ptr<B> clone( ){ return std::shared_ptr<B>( clone_impl( )); }
  14.   virtual void print( ) const { std::printf( "B: %d\n", b ); };
  15. };
  16.  
  17. class D: public B {
  18. private:
  19.   D *clone_impl( ) { return new D( *this ); }
  20. protected:
  21.   int d;
  22. public:
  23.   D( int x ): B(x), d( x*2 ){ }
  24.   D( const D &that ): B( that.b ), d( that.d ){ }
  25.   ~D( ){ }
  26.   std::shared_ptr<D> clone( ){ return std::shared_ptr<D>( clone_impl( )); }
  27.   void print( ) const { std::printf( "D: %d, %d\n", b, d ); };
  28. };
  29.  
  30. int main(){
  31.   B b(6);
  32.   D d(42);
  33.  
  34.   b.print( );
  35.   d.print( );
  36.  
  37.   B *bp = &d;
  38.   bp->print( );
  39.  
  40.   std::shared_ptr<B> bfromb = b.clone( );
  41.   std::shared_ptr<B> bfromd = d.clone( );
  42.   std::shared_ptr<D> dfromd = d.clone( );
  43. //  std::shared_ptr<D> dfromb = b.clone( ); // ERR
  44.   std::shared_ptr<B> bfrombp = bp->clone( );
  45. //  std::shared_ptr<D> dfrombp = bp->clone( ); // ERR
  46.  
  47.   bfromb->print( );
  48.   bfromd->print( );
  49.   dfromd->print( );
  50.   bfrombp->print( );
  51. }
Success #stdin #stdout 0s 3064KB
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stdin
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Standard input is empty
stdout
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B: 6
D: 42, 84
D: 42, 84
B: 6
D: 42, 84
D: 42, 84
D: 42, 84
https://ideone.com/6AMjL
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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