34.3.2 Membership Constraints
domain(
+Variables,
+Min,
+Max)

where Variables is a list of domain variables or
integers, Min is an integer or the atom
inf
(minus
infinity), and Max is an integer or the atom sup
(plus infinity). True if the variables all are elements of the
range Min..
Max. Cannot be reified.
 ?X
in
+Range 
defines a membership constraint. X is an integer or a domain
variable and Range is a ConstantRange (see Syntax of Indexicals). True if X is an element of the range.
 ?X
in_set
+FDSet 
defines a membership constraint. X is an integer or a domain
variable and FDSet is an FD set term (see FD Set Operations). True if X is an element of the FD set.
in/2
and in_set/2
constraints can be reified. They
maintain domainconsistency and their reified versions detect
domainentailment and disentailment; see The Constraint System.