How to rewrite this code without using boost?

Question

My task is to modify Sergiu Dotenco\'s Well Equidistributed Long-period Linear (WELL) algorithm code to not use boost (not saying boost is bad, but due to some company\'s policy

Answer 1

Using C++17, this code becomes way simpler and error messages are friendlier on the eye.

This is a sample implementation of Power2Modulo:

#include 

template
struct Power2Modulo
{
  static_assert(std::is_unsigned_v);
  static_assert((r & (r - 1)) == 0,
     "The second parameter of this struct is required to be a power of 2");

  template
  [[nodiscard]] static constexpr T calc(T value)
  {
    return value & (r - 1);
  }
};

You can use it like this:

int main()
{ 
  /* This code fails to compile with friendly error message
  Power2Modulo x;
  */

  // Using the static function
  using Mod16 = Power2Modulo;
  static_assert(Mod16::calc(15) == 15);
  static_assert(Mod16::calc(16) == 0);
  static_assert(Mod16::calc(17) == 1);

  // Using it like a member function
  Power2Modulo mod4;
  static_assert(mod4.calc(15) == 3);
  static_assert(mod4.calc(16) == 0);
  static_assert(mod4.calc(17) == 1);
}

Tested with clang-6 and gcc-8 and VisualC++ (via http://webcompiler.cloudapp.net/).