c++ template function with predicate support -

i want implement priority queue using template.i tried getting error , want pass custom predicate support less function.

#include <iostream>  using namespace std;  template <typename t, std::size_t n, typename lessfunction> class myclass {     typedef std::size_t     size_type; public:     void push( const t& t) {         //         size_type index ;//(some value .. 5)         //...//         if(lessfunction(m_buffer[index], t))         {             ///         }     }  private:     t m_buffer[n]; };  struct mycompare {     bool operator() (int& x, const int& y) {         return abs(x) < abs(y);     } };  int main() {     myclass<int , 8, mycompare> obj;     obj.push(1);     return 0; } 

i getting error.

/home/sanju/code/circular-buffer/main.cpp:17: error: no matching function call 'mycompare::mycompare(int&, const int&)'          if(lessfunction(m_buffer[index], t)) 

please correct me. , have 1 more question how can template use functor function lessfunction ?

you need create instance of class , use overloaded () operator in push member function.

... lessfunction f ; if (f(m_buffer[index], t)) ... 

the operator overloaded function not static member function , hence requires instance of class declared called.