I'm just wondering if it is "feasible" to inherit from NUMBER to
implement a simplified Computer Algebra System like Ginac
(http://www.ginac.de/).
The "inner" design of its expressions - the one hidden by the ex type,
is akin to "our" NUMBER class.
Except that they had to had a layer to hide reference counting and other
amenities that are avoided from the beginning by Eiffel, thanks to its
design and Garbage Collector.
