C++11: std::isinf()

C++11 added the function std::isinf() to test if a number is (+/-)infinite, and std::isfinite() to test the opposite. Here is an example:

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

int main()
{
  double one;
  double zero;

  one = 1.0;
  zero = 0.0;

  cout << std::isinf   (one /zero) << " "; // 1
  cout << std::isinf   (zero/one ) << " "; // 0

  cout << std::isfinite(one /zero) << " "; // 0
  cout << std::isfinite(zero/one ) << " "; // 1
 

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

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