| Equality operator | Succeeds if |
|---|---|
| X = Y | X can be unified with Y |
| X \= Y | X cannot be unified with Y |
| X == Y | X and Y are identical (i.e. they unify with no variable bindings occurring) |
| X \== Y | X and Y are not identical |
| X =:= Y | X and Y are arithmetically equal |
| X =\= Y | X and Y are not arithmetically equal |