C++98, 11, 14: Complex Numbers

The std::complex template class handles complex numbers. Here is an example:

// Euler's Identity: e**(i * pi) + 1 = 0
#include <complex>
#include <iostream>

const std::complex<double> I(0.0, 1.0);
const double               PI  = 3.141592653589793238463;

int main()
{
  std::complex<double> eRaisedToTheITimesPiPower;
  std::complex<double> lhs     ;
  std::complex<double> rhs     ;
  double               lhsAbs ;
  double               rhsAbs ;
  double               lhsArg ;
  double               rhsArg ;
  double               lhsReal;
  double               rhsReal;
  double               lhsImag;
  double               rhsImag;
  std::complex<double> lhs2    ;
  std::complex<double> rhs2    ;
  bool                 lhsIsEqualToRhs  ;
  bool                 lhs2IsEqualToRhs2;

  eRaisedToTheITimesPiPower = std::exp(I * PI);

  lhs     = eRaisedToTheITimesPiPower + 1.0;
  rhs     = std::complex<double>(0.0, 0.0);

  lhsAbs  = std::abs (lhs);
  rhsAbs  = std::abs (rhs);
  lhsArg  = std::arg (lhs);
  rhsArg  = std::arg (rhs);
  lhsReal = std::real(lhs);
  rhsReal = std::real(rhs);
  lhsImag = std::imag(lhs);
  rhsImag = std::imag(rhs);
  lhs2    = std::polar<double>(lhsReal, lhsImag);
  rhs2    = std::polar<double>(rhsReal, rhsImag);

  lhsIsEqualToRhs   = (lhs  == rhs );
  lhs2IsEqualToRhs2 = (lhs2 == rhs2);

  std::cout << eRaisedToTheITimesPiPower << " ";
  std::cout << lhs     << " ";
  std::cout << rhs     << " ";
  std::cout << lhsAbs  << " ";
  std::cout << rhsAbs  << " ";

  std::cout << std::endl;

  std::cout << lhsArg  << " ";
  std::cout << rhsArg  << " ";
  std::cout << lhsReal << " ";
  std::cout << rhsReal << " ";
  std::cout << lhsImag << " ";
  std::cout << rhsImag << " ";
  std::cout << lhs2    << " ";
  std::cout << rhs2    << " ";
  std::cout << lhsIsEqualToRhs  << " ";
  std::cout << lhs2IsEqualToRhs2 << " ";

  std::cout << std::endl;
  return 0;
}
// Output: (-1,1.22465e-16) (0,1.22465e-16) (0,0) 1.22465e-16 0
//         1.5708 0 0 0 1.22465e-16 0 (0,0) (0,0) 0 1

Reference: http://en.cppreference.com/w/cpp/numeric/complex