Answer to Question parameter-2

One approach is as follows.

Complex sum(const Complex& a, const Complex& b)
{
  Complex c(a.repart + b.repart, a.impart + b.impart);
  return c;
}

An alternative is the following.

Complex sum(const Complex& a, const Complex& b)
{
  return Complex(a.repart + b.repart, a.impart + b.impart);
}