Templated class: Check if complex at compile time

Question

I have a class A templated with a Scalar which can be real- or complex-valued. It has a method realPart which is supposed to return the re

Answer 1

This can be done with a simple is_complex trait and SFINAE:

template struct is_complex : std::false_type {};
template struct is_complex> : std::true_type {};

template
class A {
public:
    A(const Scalar z) : z_(z)
    { }

    template{}>* = nullptr>
    Scalar realPart()
    {
      return z_.real();
    }

    template{}>* = nullptr>
    Scalar realPart()
    {
      return z_;
    }
private:
    Scalar z_;
};