Primitive for excluding the values specified in Domain from the domains of Vars.
Domain can be a list (note only a list is supported in this primitive, and not a collection) of domain specifications, a la the domain specifications of (::)/2 -- i.e. each element can be an integer, or an integer range in the form
Lo..Hi. Alternatively, Domain can be an existing GFD domain variable, or an integer.
Note that this predicate is intended for use only in implementing co-operation with other solvers and constraint propagators at the ECLiPSe level, and should not be called from ordinary user code. It differs from the usual constraint in that the propagation is not performed immediately. Normally, propagation in gecode is performed by a suspended goal that is scheduled and woken after each constraint is posted. However, this predicate does not call the woken goal scheduler (wake/0), so the propagation goal may not be executed immediately. (It is possible that under some circumstances the goal will be executed, if wake/0 is called indirectly - one example would be by the unify handler if the variable becomes ground - but this should not be relied upon.) To ensure that the goals are eventually executed, the caller should arrange for wake/0 to be called at some appropriate point in the subsequent execution. Please see the "Advanced Control Features" section of the User Manual for more information about woken goal management.
This predicate is specific to lib(gfd). For Gecode, if multiple values need to be excluded from the domain of a variable, it is much more efficient to do it in one go, rather than excluding each value individually (e.g. using gfd_vars_exclude/2). Also, if the values has to be excluded from multiple variables, it is more efficient to use one primitive to do this, rather than exclude the values from each variable individually, as this is done with one event.