if (only == null || res == only)
for(StateNode pred : res) {
Forest[] holder = r.holder;
Forest old = pos >= holder.length ? null : holder[pos];
if (pos < holder.length) holder[pos] = res.getForest();
if (pos>0) pred.reduce(r, pos-1, target, null);
if (only == null || res == only)
for(StateNode pred : res) {
Forest[] holder = r.holder;
Forest old = pos >= holder.length ? null : holder[pos];
if (pos < holder.length) holder[pos] = res.getForest();
if (pos>0) pred.reduce(r, pos-1, target, null);