I'm implementing kruskal's algorithm and ran into some troubles compiling. I need to sort a vector of objects by value. Here is my code and the error I'm getting.

Code://These are the two functions in graph.cpp (there are more but are unrelated) #include <vector> #include <algorithm> #include <iostream> using namespace std; #include "graph.h" #include "edge.h" using std::vector; void graph::sort_edgesArray() { sort (edgesArray.begin(), edgesArray.end(), graph::cmp_val); <== This is line 39 in the error } bool graph::cmp_val (edge& a, edge& B) { return (a.val < b.val); }Code://This is the header file graph.h #ifndef GRAPH_H #define GRAPH_H #include <vector> #include "edge.h" using std::vector; class graph { public: int nEdges; int nVerts; vector<edge> edgesArray; //array that holds edges //might need a vertices vector graph() : nEdges(0), nVerts(0) {} void addVert(int vert); void addEdge(int start, int end, int value); int get_edges(); int get_verts(); void sort_edgesArray(); bool cmp_val(edge& a, edge& b); }; #endifCode://This is the edge.h header file where graph.cpp is calling from to construct the vector. #ifndef EDGE_H #define EDGE_H //Edges class in the graph class edge { public: int node1; int node2; int val; //constructor edge(int start, int end, int value) : node1(start), node2(end), val(value) {} }; //end class edge #endifCode://This is the error I'm getting. graph.cpp: In member function ‘void graph::sort_edgesArray()’: graph.cpp:39:33: error: no matching function for call to ‘sort(std::vector<edge>::iterator&, std::vector<edge>::iterator&, <unresolved overloaded function type>)’ /usr/include/c++/4.5/bits/stl_algo.h:5236:18: note: candidate is: void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<edge*, std::vector<edge> >, _Compare = bool (graph::*)(edge&, edge&)]