Linked List Calc仅评估第一个数字。 C ++

Question

我正在研究一个后缀计算器，我非常接近完成，但我很难理解为什么我的计算器只评估第一个输入。例如，如果我输入：“1 2 3 ++”，它只弹出第一个数字并显示“1”作为答案。我觉得这个问题源于主循环，其中输入和传递给堆栈的数字没有被正确推送。任何建议/提示表示赞赏！谢谢！

class Dstack
{

    public:
        Dstack();
        ~Dstack();
        void push(double value);
        bool pop(double &value);
        int size();
        bool empty();
        int top();

    private:

        class Node
        {
            public:
                Node(double value, Node *next)
                {m_value = value; m_next = next;}
                double m_value;
                Node *m_next;
        };
        Node *m_head;


};

Dstack::Dstack()
{
    m_head = NULL;
}

Dstack::~Dstack()
{
    Node *ptr = m_head;
    while (ptr != NULL)
    {
        Node *temp;

        temp = ptr;
        ptr = ptr->m_next;
        delete temp;
    }
}

void Dstack::push(double value)
{
    m_head = new Node(value, m_head);
}

bool Dstack::pop(double &value)
{
    //Node *ptr = m_head;
    if(m_head == NULL)
    {
        return false;
    }
    else
    {
            Node *temp = m_head;
            value = m_head->m_value;
            m_head = m_head->m_next;
            delete temp;
            return true;
    }
}

int Dstack::size()
{
    int num_elements = 0;

    Node *ptr = m_head;
    while(ptr != NULL)
    {
        num_elements++;
        ptr = ptr->m_next;
    }
    return num_elements;
}

bool Dstack::empty()
{
    if(m_head == NULL)
        return true;

    else
        return false;

}

//main

void error()
{
    cerr << "Illegal" << endl;
    exit(1);
}


int main()
{
    double lVal, rVal, answer;
    Dstack stack;
    double num;


    while((cin.peek()) != -1)
    {
        if(cin.peek() >= 'a' && cin.peek() <= 'z')
        {
            error();
        }
        if(isspace(cin.peek()))
        {
            cin.ignore();
            break;
        }
        if(isdigit(cin.peek()) || cin.peek() == '.')
           {
               cin >> num;
               if(cin.good())
               {
                    stack.push(num);
               }
           }
        else if(cin.peek() == '+')
        {
            rVal = stack.pop(num);
            lVal = stack.pop(num);
            answer = rVal + lVal;
            stack.push(answer);
            break;
        }
        else if(cin.peek() == '-')
        {
            rVal = stack.pop(num);
            lVal = stack.pop(num);
            answer = rVal - lVal;
            stack.push(answer);
            break;
        }
        else if(cin.peek() == '*')
        {
            rVal = stack.pop(num);
            lVal = stack.pop(num);
            answer = rVal * lVal;
            stack.push(answer);
            break;
        }
        else if(cin.peek() == '/')
        {
            rVal = stack.pop(num);
            lVal = stack.pop(num);
            answer = rVal / lVal;
            stack.push(answer);
            break;
        }
        else if(cin.peek() == '^')
        {
            rVal = stack.pop(num);
            lVal = stack.pop(num);
            answer = pow(rVal, lVal);
            stack.push(answer);
            break;
        }
        stack.pop(answer);
    }

    cout << "\nAnswer: " << answer << endl;
    return 0;
}