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<class T> struct is_complex : std::false_type {};
template<class T> struct is_complex<std::complex<T>> : std::true_type {};

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

    template<class S = Scalar, std::enable_if_t<is_complex<S>{}>* = nullptr>
    Scalar realPart()
    {
      return z_.real();
    }

    template<class S = Scalar, std::enable_if_t<!is_complex<S>{}>* = nullptr>
    Scalar realPart()
    {
      return z_;
    }
private:
    Scalar z_;
};