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# exclude_range(?Var, ++Lo, ++Hi)

Exclude the elements Lo..Hi from the domain of Var.

Var
  Existing domain variable or integer
Lo
  Integer lower bound of range to exclude
Hi
  Integer upper bound of range to exclude

## Description

This predicate is mainly provided for compatibility with IC solver. If you want to exclude the same range of values from multiple variables, it is more efficient to use the lib(gfd) specific gfd_vars_exclude_range/3.

Primitive for excluding the integers between Lo and Hi (inclusive) from the domain of an integer variable. The call may fail (when the domain of Var has no elements outside the range Lo..Hi), succeed (possibly updating the variable's domain), or instantiate the variable (in the case where the domain gets restricted to a singleton value).

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, exclude_range/3 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.

## See Also

exclude / 2, impose_min / 2, impose_max / 2