Description: Define the class of subcomplex modules, which are left modules over a
subring of the field of complex numbers CCfld , which allows us to
use the complex addition, multiplication, etc. in theorems about
subcomplex modules. Since the field of complex numbers is commutative
and so are its subrings (see subrgcrng ), left modules over such
subrings are the same as right modules, see rmodislmod . Therefore,
we drop the word "left" from "subcomplex left module". (Contributed by Mario Carneiro, 16-Oct-2015)