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  1. #include <iostream>
  2.  
  3. class Rectangle
  4. {
  5.      public:
  6.      Rectangle(double w = 0, double h = 0, double r = 0) : width(w), height(h), radius(r)
  7.      {}
  8.  
  9.      double width;
  10.      double height;
  11.      double radius;
  12. };
  13.  
  14. namespace traits
  15. {
  16.     template <typename P>
  17.     struct operations
  18.     {
  19.         static void display(Rectangle const &, std::ostream &);
  20.         static double area(Rectangle const &);
  21.     };
  22.  
  23.     template <typename P, int N>
  24.     struct access {};
  25. }
  26.  
  27. namespace traits
  28. {
  29.     template <int N>
  30.     struct access<Rectangle, N>
  31.     {
  32.         static double get(Rectangle const &);
  33.     };
  34. }
  35.  
  36. namespace traits
  37. {
  38.     template <>
  39.     struct access<Rectangle, 0>
  40.     {
  41.         static double get(Rectangle const &rect)
  42.         {
  43.             return rect.width;
  44.         }
  45.     };
  46.  
  47.     template <>
  48.     struct access<Rectangle, 1>
  49.     {
  50.         static double get(Rectangle const &rect)
  51.         {
  52.             return rect.height;
  53.         }
  54.     };
  55. }
  56.  
  57. namespace traits
  58. {
  59.     template <>
  60.     struct operations<Rectangle>
  61.     {
  62.         static void display(Rectangle const &rect, std::ostream &os)
  63.         {
  64.             os << "Width of rectangle: " << rect.width << std::endl;
  65.             os << "Height of rectangle: " << rect.height << std::endl;
  66.             os << "Area of rectangle: " << area(rect) << std::endl; 
  67.         }
  68.         static double area(Rectangle const& rect)
  69.         {
  70.             double width  =  access<Rectangle, 0>::template get<0>(rect);
  71.             double height =  access<Rectangle, 1>::template get<1>(rect);
  72.  
  73.             return width * height;
  74.         }
  75.     };
  76. }
  77.  
  78. template <int N, typename P>
  79. static inline double get(P const &p)
  80. {
  81.     return traits::access<P, N>::get(p);
  82. }
  83.  
  84. template <typename P>
  85. static inline void display(P const &p)
  86. {
  87.     traits::operations<P>::display(p, std::cout);
  88. }
  89.  
  90. template <typename P>
  91. static inline double area(P const &p)
  92. {
  93.     return traits::operations<P>::area(p);
  94. }
  95.  
  96. /*ostream & operator<<(ostream & out, Shape const& s)
  97. {
  98.       s.display(out);
  99.       return out;
  100. }*/
  101.  
  102.  
  103. int main()
  104. {
  105.  
  106. }
Compilation error #stdin compilation error #stdout 0s 2848KB
comments (?)
stdin
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Standard input is empty
compilation info 
prog.cpp: In static member function ‘static double traits::operations<Rectangle>::area(const Rectangle&)’:
prog.cpp:70:52: error: ‘template’ (as a disambiguator) is only allowed within templates
prog.cpp:70:72: error: no match for ‘operator>’ in ‘false > rect’
prog.cpp:70:72: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses]
prog.cpp:71:52: error: ‘template’ (as a disambiguator) is only allowed within templates
prog.cpp:71:65: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
prog.cpp:71:72: error: no match for ‘operator>’ in ‘(traits::access<Rectangle, 1>::get == 0u) > rect’
prog.cpp:71:72: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses]
stdout
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Standard output is empty
https://ideone.com/WFlnb2
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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