@Override
 public double computeValue(ReadOnlyDatabase db, GroundTerm... args) {
   return extFun.getValue(db, args);
 }
 /**
  * Sole constructor.
  *
  * @param name the name of this predicate
  * @param extFun the ExternalFunction to use to compute truth values
  * @see PredicateFactory
  */
 ExternalFunctionalPredicate(String name, ExternalFunction extFun) {
   super(name, extFun.getArgumentTypes());
   this.extFun = extFun;
 }