return relprod0((BuDDyBDD) that, (BuDDyBDD) var);
BuDDyBDD c = (BuDDyBDD) that; BuDDyBDD d = (BuDDyBDD) var; int b = relprod0(_id, c._id, d._id); return new BuDDyBDD(b);
        public BDD relprod(BDD that, BDD var) {            return relprod0((BuDDyBDD) that, (BuDDyBDD) var);        }