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  1. /** Set max/min using bitwise operations.
  2.  *
  3.  * $ c++ -std=c++14 *.cc && ./a.out
  4.  *
  5.  */
  6. #include <iostream>
  7. #include <type_traits>
  8.  
  9. namespace
  10. {
  11.   template <typename T, bool = std::is_unsigned<T>::value>  class bitwise_limits {
  12.   public:
  13.     static constexpr T max() noexcept { return T(); }
  14.     static constexpr T min() noexcept { return T(); }
  15.  
  16.   };
  17.  
  18.   // unsigned specialization
  19.   template <typename T>
  20.   class bitwise_limits<T, true> {
  21.   public:
  22.     static constexpr T max() noexcept { return ~T(0); }  // all bits set
  23.     static constexpr T min() noexcept { return  T(0); }  // all bits clear
  24.   };
  25.  
  26.   // signed specialization
  27.   template <typename T>
  28.   class bitwise_limits<T, false> {
  29.   public:
  30.     static constexpr T max() noexcept { // all bits set except sign
  31.       return bitwise_limits<std::make_unsigned_t<T>>::max() >> 1;
  32.     }
  33.     static constexpr T min() noexcept {
  34.       return ~max(); // all bits clear except sign
  35.     }
  36.  
  37.   };
  38. }
  39.  
  40.  
  41. int main()
  42. {
  43.   std::cout << (int)bitwise_limits<uint8_t>::max() << '\n';
  44.   std::cout << (int)bitwise_limits<uint8_t>::min() << '\n';
  45.   std::cout << (int)bitwise_limits< int8_t>::max() << '\n';
  46.   std::cout << (int)bitwise_limits< int8_t>::min() << '\n';
  47. }
  48.  
Success #stdin #stdout 0s 15240KB
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https://ideone.com/eBUhcS
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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