Assignment

constexpr kc_interval<T>& operator=(const kc_interval<T>&) = default; 
constexpr kc_interval<T>& operator=(const std::pair<std::complex<T>,T>&)

The following assignment operators are implemented:

operator=(const kc_interval<T>&): Standard assignment operator.
operator=(const std::pair<std::complex<T>,T>&): Assignment operator from a std::pair.