src/org/nutz/el/arithmetic/RPN.java
private LinkedList<Object> OperatorTree(Queue<Object> rpn){
        LinkedList<Object> operand = new LinkedList<Object>();
        while(!rpn.isEmpty()){
            if(rpn.peek() instanceof Operator){
                Operator opt = (Operator) rpn.poll();
                opt.wrap(operand);
                operand.addFirst(opt);
                continue;
            }
            if(rpn.peek() instanceof Elobj){
                ((Elobj) rpn.peek()).setEc(ec);
            }
            operand.addFirst(rpn.poll());
        }
        return operand;
    }
private LinkedList<Object> OperatorTree(Queue<Object> rpn){
        LinkedList<Object> operand = new LinkedList<Object>();
        while(!rpn.isEmpty()){
            if(rpn.peek() instanceof Operator){
                Operator opt = (Operator) rpn.poll();
                opt.wrap(operand);
                operand.addFirst(opt);
                continue;
            }
            if(rpn.peek() instanceof Elobj){
                ((Elobj) rpn.peek()).setEc(ec);
            }
            operand.addFirst(rpn.poll());
        }
        return operand;
    }
转换成操作树