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  1. namespace interval
  2. {
  3.  
  4. namespace detail
  5. {
  6.  
  7. template < typename T >
  8. struct result_
  9. {
  10. protected:
  11.     const bool value;
  12.     const T    &item_;
  13.  
  14.     result_( bool p, const T &itm )
  15.       : value( p ), item_( itm ) {}
  16.  
  17.     explicit
  18.     operator bool( void ) const
  19.     { return this->value; }
  20. };  
  21.  
  22. template < typename T >
  23. struct is_lt_or_leq
  24.   : private result_< T >
  25. { 
  26.     template < typename U >
  27.     bool
  28.     friend operator>( is_lt_or_leq< U > &&, const U & );
  29.     template < typename U >
  30.     bool
  31.     friend operator>=( is_lt_or_leq< U > &&, const U & );
  32.  
  33.     is_lt_or_leq( bool p, const T &itm )
  34.       : result_< T >( p, itm ) {}
  35.  
  36.     using result_< T >::operator bool;
  37. };
  38.  
  39. template < typename T >
  40. struct is_gt_or_geq
  41.   : private result_< T >
  42. {   
  43.     template < typename U >
  44.     bool
  45.     friend operator<( is_gt_or_geq< U > &&, const U & );
  46.     template < typename U >
  47.     bool
  48.     friend operator<=( is_gt_or_geq< U > &&, const U & );
  49.  
  50.     is_gt_or_geq( bool p, const T &itm )
  51.       : result_< T >( p, itm ) {}
  52.  
  53.     using result_< T >::operator bool;
  54. };
  55.  
  56. template < typename T >
  57. struct interval_item
  58. {
  59.     template < typename U >
  60.     bool
  61.     friend operator>( interval_item< U > &&, const U & );
  62.     template < typename U >
  63.     is_lt_or_leq< U >
  64.     friend operator>( const U &, interval_item< U > && );
  65.  
  66.     template < typename U >
  67.     bool
  68.     friend operator>=( interval_item< U > &&, const U & );
  69.     template < typename U >
  70.     is_lt_or_leq< U >
  71.     friend operator>=( const U &, interval_item< U > && );
  72.  
  73.     template < typename U >
  74.     bool
  75.     friend operator<( interval_item< U > &&, const U & );
  76.     template < typename U >
  77.     is_gt_or_geq< U >
  78.     friend operator<( const U &, interval_item< U > && );
  79.  
  80.     template < typename U >
  81.     bool
  82.     friend operator<=( interval_item< U > &&, const U & );
  83.     template < typename U >
  84.     is_gt_or_geq< U >
  85.     friend operator<=( const U &, interval_item< U > && );
  86.  
  87. private:
  88.     const T &item_;
  89.  
  90. public:
  91.     interval_item( const T &itm )
  92.       : item_( itm ) {}
  93.  
  94.     interval_item( const interval_item & );
  95.     interval_item( interval_item && );
  96.  
  97.     interval_item &
  98.     operator=( const interval_item & );
  99.     interval_item &
  100.     operator=( interval_item && );
  101. };
  102.  
  103. template < typename T >
  104. interval_item< T >
  105. item( const T &itm )
  106. { return { itm }; }
  107.  
  108. template < typename T >
  109. bool
  110. operator>( interval_item< T > &&item, const T &x )
  111. { return item.item_ > x; }
  112.  
  113. template < typename T >
  114. is_lt_or_leq< T >
  115. operator>( const T &x, interval_item< T > &&item )
  116. { return { x > item.item_, item.item_ }; }
  117.  
  118. template < typename T >
  119. bool
  120. operator>( is_lt_or_leq< T > &&prev, const T &x )
  121. { return prev.value && prev.item_ > x; }
  122.  
  123.  
  124. template < typename T >
  125. bool
  126. operator>=( interval_item< T > &&item, const T &x )
  127. { return item.item_ >= x; }
  128.  
  129. template < typename T >
  130. is_lt_or_leq< T >
  131. operator>=( const T &x, interval_item< T > &&item )
  132. { return { x >= item.item_, item.item_ }; }
  133.  
  134. template < typename T >
  135. bool
  136. operator>=( is_lt_or_leq< T > &&prev, const T &x )
  137. { return prev.value && prev.item_ >= x; }
  138.  
  139.  
  140. template < typename T >
  141. bool
  142. operator<( interval_item< T > &&item, const T &x )
  143. { return item.item_ < x; }
  144.  
  145. template < typename T >
  146. is_gt_or_geq< T >
  147. operator<( const T &x, interval_item< T > &&item )
  148. { return { x < item.item_, item.item_ }; }
  149.  
  150. template < typename T >
  151. bool
  152. operator<( is_gt_or_geq< T > &&prev, const T &x )
  153. { return prev.value && prev.item_ < x; }
  154.  
  155.  
  156. template < typename T >
  157. bool
  158. operator<=( interval_item< T > &&item, const T &x )
  159. { return item.item_ <= x; }
  160.  
  161. template < typename T >
  162. is_gt_or_geq< T >
  163. operator<=( const T &x, interval_item< T > &&item )
  164. { return { x <= item.item_, item.item_ }; }
  165.  
  166. template < typename T >
  167. bool
  168. operator<=( is_gt_or_geq< T > &&prev, const T &x )
  169. { return prev.value && prev.item_ <= x; }
  170.  
  171. } // namespace detail
  172.  
  173. using ::interval::detail::item;
  174.  
  175. } // namespace interval
  176.  
  177. #include <iostream>
  178. using namespace std;
  179.  
  180. int
  181. main( void )
  182. {   
  183.     cout << boolalpha
  184.          << static_cast< bool >( -1 < interval::item( 0 ) < 1 )
  185.          << endl;
  186. }
  187.  
Success #stdin #stdout 0s 2828KB
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https://ideone.com/kWZVF
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
secret

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