A constraint is called as any other Prolog predicate. When called, the constraint is posted to the store. For example:
| ?- X in 1..5, Y in 2..8, X+Y #= T.
X in 1..5,
Y in 2..8,
T in 3..13
| ?- X in 1..5, T in 3..13, X+Y #= T.
X in 1..5,
T in 3..13,
Y in -2..12
Note that the answer constraint shows the domains of nonground query variables, but not any constraints that may be attached to them.