A simple interval arithmetic which handles
partial functions gracefully is
:
for any 
: every member
of 
may be described as a member of 
.
Furthermore, any non-trivial 
warrants the full descriptive power of .
A trivial may be simulated by appropriately constructing
models.
Consider the square root operator, denoted here as g.
It is a unary partial function, undefined for negative arguments.
Consider using 
: 
is
undefined if j contains only negative numbers. Consider the
following examples:
| Jeff Tupper | March 1996 |