7-2 friend functions (time class)

/*
* Copyright and version Declaration of the program
* Copyright (c) 2011, a student from the computer College of Yantai University
* All Rights Reserved.
* File Name:
* Author: Zhang chuanxin
* Completion date: January 1, April 02, 2012
* Version: 1.0

* Description of tasks and Solutions
* Input description:
* Problem description: differences between using member functions, friend functions, and general functions
* Program output:
* Problem Analysis :......
* Algorithm Design :......
*/

# Include <iostream> # include <cmath> using namespace STD; Class cpoint {PRIVATE: Double X; // abscissa Double Y; // ordinate public: cpoint (double xx = 1, double YY = 2): X (XX), y (yy) {} double distance1 (cpoint P, cpoint Q); // the distance between two points: Friend double distance2 (cpoint P, cpoint Q); // you can declare int getx () {return X;} int Gety () {return y;} void input (); // use X, Y form input coordinate point void output (); // output coordinate point in the form of (x, y)}; double distane3 (cpoint P, CP Oint Q); // General function declaration void main () {cpoint A1; cpoint A2; a1.input (); a1.output (); a2.input (); a2.output (); a1.distance1 (A1, a2); distance2 (a1, a2); distane3 (a1, a2); System ("pause");} void cpoint: input () {char; cout <"Enter coordinate points in the form of" X, Y ":" <Endl; CIN> x> A> Y; if (! = ',') {Exit (0) ;}// output coordinate point void cpoint: output () in the form of (x, y () {cout <"(" <x <"," <Y <")" <Endl ;}// distance between two points (one point is the current point, another point is the parameter P) Double cpoint: distance1 (cpoint P, cpoint q) // Implementation of the member function, before distance1 add cpoint :: {cout <"the distance between two points is:" <Endl; cout <SQRT (Q. x-p.x) * (Q. x-p.x) + (Q. y-p.y) * (Q. y-p.y) <Endl; return 0;} double distance2 (cpoint P, cpoint q) // implementation of the youyuan function, distance2 without cpoint ::, it is not a member function of the class {cout <"the distance between two points is:" <Endl; cout <SQRT (Q. x-p.x) * (Q. x-p.x) + (Q. y-p.y) * (Q. y-p.y) <Endl; return 0;} double distan2010( cpoint P, cpoint q) // only public interface Q can be used. getx () access private data member {cout <"two points:" <Endl; cout <SQRT (Q. getx ()-P. getx () * (Q. getx ()-P. getx () + (Q. gety ()-P. gety () * (Q. gety ()-P. gety () <Endl; return 0 ;}

Running result:

Experience Accumulation:
1. In the three versions, finding the distance between two points makes my use of these three functions clearer.

Computer comments: the friend function makes the relationship between two "persons" closer...