Question

我试图编写一个c ++优先级队列实现。

这是优先级队列元素的类：

template <class Priority, class T>
class PriorityQueueElement {

public:
Priority priority;
T* data;

private:
    PriorityQueueElement* next ;
public:

    PriorityQueueElement( const Priority& priority,T data ) :
        priority(priority) ,data(&data) , next(NULL){
    }
    // ... other functions .. //
    template <class P, class Y>
    friend ostream& operator<<(ostream& os ,const PriorityQueueElement<P,Y>& element);

};

和功能：

template<class Priority, class T>
ostream& operator<<(ostream& os ,const PriorityQueueElement<Priority,T>& elemen){
        return os << "[" << elemen.getPriority() << "," << elemen.getData( ) << "]";
}

我得到错误：

Multiple markers at this line
    - template argument deduction/substitution failed:
    - template<class Priority, class T> std::ostream& mtm::operator<<(std::ostream&, const 
 mtm::PriorityQueueElement<Priority, T>&)
Multiple markers at this line
    - required from 'std::ostream& mtm::operator<<(std::ostream&, const mtm::PriorityQueueElement<Priority, T>&) [with Priority = int; T = int; std::ostream = 
 std::basic_ostream<char>]'
    - required from 'std::ostream& mtm::operator<<(std::ostream&, const mtm::PriorityQueueElement<Priority, T>&) [with Priority = double; T = Student; 
 std::ostream = std::basic_ostream<char>]'

如果我尝试使用：

template <class Priority,class T>

我收到关于在类本身中隐藏模板的错误

谢谢你的帮助！

Answer 1

我复制了你的代码并修改了一下（用于测试）

template<class Priority, class T>
    ostream& operator<<(ostream& os, const PriorityQueueElement<Priority, T>& elemen)
    {
        return os << "[" << elemen.priority << "," << *elemen.data << "]";
    }

它的工作，主要是我把：

PriorityQueueElement<int, const char*> x( 1, "fsdfsdfsd" );
cout << x;

它给了我输出：[1，fsdfsdfsd]

在visual studio 2013上测试。问题可能在其他地方

尝试重载时的问题＆lt;＆lt; c ++ 11中的operator

1 个答案: