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  1. #include <stdio.h>
  2.  
  3. #define USE_CAST_OP
  4.  
  5. class Float;
  6. class Double
  7. {
  8.     double m_Value;
  9. public:
  10.     Double() : m_Value( 0.0 ){}
  11.     explicit Double( double d ) : m_Value( d ){}
  12.     #ifdef USE_CAST_OP
  13.     explicit
  14.     #endif
  15.     Double( const Float& f );
  16.     double GetValue( void ) const { return m_Value; }
  17.     Double operator +( const Double& other ){ printf( "Double::operator+(Double)\n" ); return Double( m_Value + other.m_Value ); }
  18.     #ifdef USE_CAST_OP
  19.     operator Float();
  20.     #endif
  21. };
  22. class Float
  23. {
  24.     float m_Value;
  25. public:
  26.     Float() : m_Value( 0.0f ){}
  27.     explicit Float( float f ) : m_Value( f ){}
  28.     #ifdef USE_CAST_OP
  29.     explicit
  30.     #endif
  31.     Float( const Double& d ) : m_Value( d.GetValue() ){}
  32.     float GetValue( void ) const { return m_Value; }
  33.     Float  operator +( const Float&  other ){ printf( "Float::operator+(Float)\n" ); return Float( m_Value + other.m_Value ); }
  34.     Double operator +( const Double& other ){ printf( "Float::operator+(Double)\n" ); return Double( m_Value + other.GetValue() ); }
  35.     #ifdef USE_CAST_OP
  36.     operator Double(){ printf( "Float to Double\n" ); return Double(); }
  37.     #endif
  38. };
  39.  
  40. Double::Double( const Float& f ) : m_Value( f.GetValue() ){}
  41. #ifdef USE_CAST_OP
  42. Double::operator Float(){ printf( "Double to Float\n" ); return Float(); }
  43. #endif
  44.  
  45. // Double operator +( Double left, Double right ){ printf( "::operator+(Double,Double)\n" ); return Double(); }
  46.  
  47. void PrintType( const Double& d ){ printf( "Result : Double\n" ); }
  48. void PrintType( const Float&  f ){ printf( "Result : Float\n" ); }
  49.  
  50. void RequireFloat( const Float& f ){  }
  51. void RequireDouble( const Double& d ){  }
  52.  
  53. int main( void )
  54. {
  55.     Double  d;
  56.     Float   f;
  57.  
  58.     printf( "[0]\n" ); 
  59.     PrintType( f + f );
  60.  
  61.     printf( "[1]\n" ); 
  62.     PrintType( d + d );
  63.  
  64.     printf( "[2]\n" );
  65.     PrintType( d + f ); // fはDoubleへ暗黙の型変換が発生する。
  66.  
  67.     printf( "[3]\n" );
  68.     PrintType( f + d ); // fはDoubleへ暗黙の型変換が発生する。
  69.  
  70.     printf( "[4]\n" );
  71.     RequireFloat ( d );
  72.     RequireDouble( f );
  73.  
  74.     return 0;
  75. }
Success #stdin #stdout 0s 3296KB
comments (?)
stdin
copy 
Standard input is empty
stdout
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[0]
Float::operator+(Float)
Result : Float
[1]
Double::operator+(Double)
Result : Double
[2]
Float to Double
Double::operator+(Double)
Result : Double
[3]
Float::operator+(Double)
Result : Double
[4]
Double to Float
Float to Double
https://ideone.com/IL1t5i
language:
C++ (gcc 8.3)
created:
10 years ago
visibility:
secret

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