最后声明

				// E-6-4-1.cpp : 定义控制台应用程序的入口点。
				//
				
				#include "stdafx.h"
				#include 
				using namespace std;
				class Point1;
				class Point2;
				class Point1{
				  int m,n;
				public:
					Point1(int x,int y){
					m=x,n=y;}
					friend void distan(Point1 a,Point2 b);
				};
				class Point2{
				  int m,n;
				public:
					Point2(int x,int y){
					m=x,n=y;}
					friend void distan(Point1 a,Point2 b);
				};
				
				void distan(Point1 a,Point2 b)
				{ 
				  cout				  cout				  }
				
				void main()
				{Point1 k(3,7);
				 Point2 j(4,5);
				 distan(k,j);
				 system("pause");
				}