A variation of 
is the number system 
:
The number system
generalizes the number system
by allowing a set of constraints to describe an interval's domain.
Each interval
can be described by a value 
and a set of domain constraints 
,
with 
and 
.
Parameter value 
is in the domain of interval
if
and 
demote from 
to
. As before, 
and must preserve domain classifications.
The implementation of models is simpler in
than in .
A description of a simple implementation of a model
, of function 
,
follows.
would return an interval with a domain described by
.
would return an interval with a domain described by
,
where 
is a domain constraint introduced by
.
| Jeff Tupper | March 1996 |