Extended interval arithmetic may be used to render graphs.
Extended interval arithmetic is similar to 
,
with the restriction that each interval set contain
either one or two intervals. If the set contains two intervals,
one interval must contain 
; the other interval must
contain 
.
An algorithm employing
extended interval arithmetic may readily graph specifications
given using +, -, 
, and 
; the more general
interval sets are needed if operations such as 
or 
may occur in a specification.
| Jeff Tupper | March 1996 |