precision.hh

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// -*- tab-width: 4; indent-tabs-mode: nil -*-
#ifndef HDNUM_PRECISION_HH
#define HDNUM_PRECISION_HH
 
namespace hdnum {
 
  // find largest eps such that 0.5 + eps > 0.5
  template<typename X>
  int precision (X& eps)
  {
        X x,large,largex,two;
        large = 0.5;
        two = 2.0;
        x = 0.5;
        largex = large+x;
        int i(0);
        while (largex>large)
          {
                eps = x;
                i = i+1;
                //              std::cout << i << " " << std::scientific << std::showpoint 
                //                << std::setprecision(15) << large+x << " " << x << std::endl;
                x = x/two;
                largex = large+x;
          }
        return i;
  } 
 
} // namespace hdnum
 
#endif