15.2.1 FD-Membership

Finite domain variables are variables that can denote one member of a finite set of integers. They can be used to express a simple form of disjunction. This form of disjunction is important when it comes to distribution.

A finite domain variable is a variable whose value is a natural number. Furthermore, the value of a finite domain variable can be constrained by some finite domain of natural numbers. For instance, the FD-membership constraint

X :: 1#5

is equivalent to $X\in\{1,2,3,4,5\}$ which in turn is equivalent to the disjunction:

$X=1 \vee X=2 \vee X=3 \vee X=4 \vee X=5$

An FD-membership constraint such as X :: 1#5 can be represented directely in the Oz constraint store. It is neither a propagator nor does it raise any case distinction.