?Var in +DomainVar is an element of Domain. Domain is 
one of:
- Integer
 - Singleton set consisting only of Integer.
 
- Lower .. Upper
 - All integers I such that Lower 
=< I =< Upper.
Lower must be an integer or the atom inf, which 
denotes negative infinity. Upper must be an integer or 
the atom sup, which denotes positive infinity. 
- Domain1 
\/ Domain2 - The union of Domain1 and Domain2.
 
[det]in(+TupleList, 
-Tuple)As in/1 but succeeds when any one of 
the tuples in TupleList is available. Tuple is 
unified with the fetched tuple.