gistfile1

Iterator it1 = left.oneStepRewrite().iterator();
            while(it.hasNext()){
                s.add(new Addition(it.next(), right));
            }
        
        
            Iterator<Expr> it2 = right.oneStepRewrite().iterator();        
            while(it.hasNext()){
                s.add(new Addition(left, it.next()));
            }