# Constexpr domain source

Back in The constructor, we declared but did not implement a `.get()` function which returns a constexpr static instance of the domain. We implement this now:

    // 100% constexpr instantiation
    constexpr _file_io_error_domain file_io_error_domain;
    inline constexpr const _file_io_error_domain &_file_io_error_domain::get()
    {
      return file_io_error_domain;
    }

View this code on Github

As this is 100% constexpr, it can be (and is under optimisation) implemented entirely in the mind of the compiler with no run time representation.

Last revised: January 26, 2019 at 23:38:56 UTC