C++17: std::optional

C++17 added a template class that creates objects with optional values. Here is an example:

#include <iostream>
#include <optional>

int main()
{  
  std::optional<int> optionalInt;
  int                Int        ;

  Int = optionalInt.value_or(-1);
  std::cout << Int                     << " ";
  std::cout << optionalInt.has_value() << " ";
  try
  {
    Int = optionalInt.value();
  }
  catch(std::bad_optional_access e)
  {
    std::cout << "bad ";
  }
  std::cout << ": ";
  optionalInt = std::optional<int>(3);
  Int         = optionalInt.value_or(-1);
  std::cout << Int                     << " ";
  std::cout << optionalInt.has_value() << " ";
  try
  {
    Int = optionalInt.value();
  }
  catch(std::bad_optional_access e)
  {
    std::cout << "bad ";
  }
  std::cout << std::endl;
  return 0;
}
// Output: -1 0 bad : 3 1

References:
https://en.wikipedia.org/wiki/C%2B%2B17
http://en.cppreference.com/w/cpp/utility/optional/value