## 5.4 Set Expressions

In most positions where a set or set variable is expected one can also
use a set expression. A set expression is composed from ground sets
(integer lists), set variables, and the following set operators:
Set1 /\ Set2 % intersection
Set1 \/ Set2 % union
Set1 \ Set2 % difference

When such set expressions occur, they are translated into auxiliary
**intersection/3**,
**union/3** and
**difference/3**
constraints, respectively.