10.9.14 Coexisting with Attributes and Blocked Goals

Domain variables may have attributes from other modules, as well as blocked goals, attached to them. As usual, they are woken up if those variables are fixed by propagation. The CLPFD propagation phase runs to fixpoint before waking anything up. At fixpoint, any attribute handlers and blocked goals for variables that were fixed by propagation are executed before search continues.

See also the verify_attributes/3 hook at lib-atts.

Please note: fd_purge(X) (see Forgetting Constraints) does not affect attributes of other modules, or blocked goals.

Please note: the garbage collector will preserve all variables with attached attributes or blocked goals, even if they are not otherwise reachable.