A.8.17.2 Membership constraints
If you are using CLP(FD) to model and solve combinatorial tasks, then you typically need to specify the admissible domains of variables. The membership constraints in/2 and ins/2 are useful in such cases.
- ?Var in +Domain
 - Var 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.
 
 - +Vars ins +Domain
 - The variables in the list Vars are elements of Domain. See in/2 for the syntax of Domain.