If you want to define a binary method for a particular class, then
define that binary method by instantiating the following instance-method pattern:
name anArgument
...
If you want to define a new numberlike class, then define the class to
be a subclass of the Magnitude class, and then implement an
instance-creation method with a name that mimics the ordinary word or
abbreviation used to denote the units involved, and then implement the
appropriate binary methods.