c++ - Why my code using priority_queue cannot compile? -

try use priority_queue. code is:

    struct heapnode     {         int val;         int row;         int col;         heapnode(int a, int b, int c) : val(a), row(b), col(c) {}     };      class mycomparator     {      public:         bool operator()(heapnode &n1, heapnode &n2)         {             return n1.val < n2.val;         }     };      void myfunction()     {          std::priority_queue<heapnode, std::vector<heapnode>,  mycomparator> hp1;   //line1         std::priority_queue<heapnode, mycomparator> hp2; //line2     } 

tried 2 ways shown on line1 , line2. neither line can pass compilation.

std::priority_queue takes 3 arguments in constructor:

template<     class t,     class container = std::vector<t>,     class compare = std::less<typename container::value_type> > class priority_queue; 

in case line1 looks fine , should compile. error message?

in line2 trying create std::priority_queue of custom type (heapnode) container "mycomparator" (not container!).

the type of underlying container use store elements. container must satisfy requirements of sequencecontainer. additionally, must provide following functions usual semantics: front(), push_back(), pop_back(). standard containers std::vector , std::deque satisfy these requirements.

http://en.cppreference.com/w/cpp/container/priority_queue

"mycomparator" not container , doesn't support required methods.

i checked code line2 commented out , compiles. have included , ? have main function somewhere?