C++11: std::fpclassify()

C++11 added the function std::classify(). It classifies a floating point number. Here is an example:

#include <cfloat>
#include <cmath>
#include <iostream>
using namespace std;

int main()
{
  cout << fpclassify( 0.0       ) << " "; //  0 (=FP_ZERO     )
  cout << fpclassify(-0.0       ) << " "; //  0 (=FP_ZERO     )
  cout << fpclassify(-42.0      ) << " "; // -1 (=FP_NORMAL   )
  cout << fpclassify(DBL_MIN/2.0) << " "; // -2 (=FP_SUBNORMAL)
  cout << fpclassify(NAN        ) << " "; //  2 (=FP_NAN      )
  cout << fpclassify(INFINITY   ) << " "; //  1 (=FP_INFINITE )

  cout << ": ";

  cout << (0.0                 == -0.0               ) << " "; // 1
  cout << (DBL_MIN/2.0         == DBL_MIN            ) << " "; // 0
  cout << (DBL_MIN/2.0         == DBL_MIN/4.0        ) << " "; // 0
  cout << (DBL_MIN/DBL_MAX/2.0 == DBL_MIN/DBL_MAX/4.0) << " "; // 1

  cout << endl;
  return 0;
}
// Output: 0 0 -1 -2 2 1 : 1 0 0 1

Reference: http://en.cppreference.com/w/cpp/numeric/math/fpclassify