C++ Primer Plus(再谈重载-一个矢量类)

跟着书敲了一个矢量类，记录如下:
Vector要实现矢量的基本运算，最重要的是为后面实现Drunkard Walk problem打下基础，从这个简单的例子中体会一些OOP思想的运用。

//vect.h#ifndef VECTOR_H#define VECTOR_H#include<iostream>namespace VECTOR{    class Vector {    public:        enum Mode { RECT, POL };        //rectangular mode polar mode    private:        double x;        double y;        double mag;//magnitude of Vector        double ang;//direction of Vector in degrees        Mode mode;//RECT or POL        void set_mag();        void set_ang();        void set_x();        void set_y();    public:        Vector();        Vector(double n1, double n2, Mode form = RECT);        void reset(double n1, double n2, Mode form = RECT);        ~Vector();        double xval()const { return x; }        double yval()const { return y; }        double magval()const{return mag;}        double angval()const { return ang; }        void polar_mode();        void rect_mode();        //operator overloading        Vector operator+(const Vector & b)const;        Vector operator-(const Vector & b)const;        Vector operator-()const;//reverse sign of Vector        Vector operator*(double n)const;        //friends        friend Vector operator*(double n, const Vector & a);        friend std::ostream &            operator<<(std::ostream & os, const Vector & v);    };}#endif

// vector.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include"vect.h"using std::sqrt;using std::sin;using std::cos;using std::atan;using std::cout;namespace VECTOR {    //compute degrees    const double Rad_to_deg = 45.0 / atan(1.0);    void Vector::set_mag() {        mag = sqrt(x * x + y * y);    }    void Vector::set_ang() {        if (x == 0.0 && y == 0.0)            ang = 0.0;        else            ang = atan2(y, x);    }    //set x from polar coordinate    void Vector::set_x()    {        x = mag * cos(ang);    }    void Vector::set_y()    {        y = mag * sin(ang);    }    Vector::Vector() {        x = y = mag = ang = 0.0;        mode = RECT;    }    Vector::Vector(double n1, double n2, Mode form)    {        mode = form;        if (form == RECT)        {            x = n1;            y = n2;            set_mag();            set_ang();        }        else if (form == POL)        {            mag = n1;            ang = n2 / Rad_to_deg;            set_x();            set_y();        }        else        {            cout << "Incorrect 3rd argument to Vector() --";            cout << " Vector set to 0 \n";            x = y = mag = ang = 0.0;            mode = RECT;        }    }    void Vector::reset(double n1, double n2, Mode form)    {        mode = form;        if (form == RECT)        {            x = n1;            y = n2;            set_mag();            set_ang();        }        else if (form == POL) {            mag = n1;            ang = n2 / Rad_to_deg;            set_x();            set_y();        }        else        {            cout << "Incorrect 3rd argument to Vector() --";            cout << " Vector set to 0 \n";            x = y = mag = ang = 0.0;            mode = RECT;        }    }    Vector::~Vector() {};    void Vector::polar_mode()    {        mode = POL;    }    void Vector::rect_mode() {        mode = RECT;    }    //operator overloading    Vector Vector::operator+(const Vector & b)const    {        return Vector(x + b.x, y + b.y);    }    Vector Vector::operator-(const Vector & b)const    {        return Vector(x - b.x, y - b.y);    }    Vector Vector::operator-()const    {        return Vector(-x, -y);    }    Vector Vector::operator*(double n)const    {        return Vector(n * x, n * y);    }    //multiply n by Vector a    Vector operator*(double n, const Vector & a)    {        return n * a;    }    std::ostream & operator<<(std::ostream & os, const Vector & v)    {        if (v.mode == Vector::RECT)            os << "(x,y) = (" << v.x << "," << v.y << ")";        else if (v.mode == Vector::POL)        {            os << "(m,a) = (" << v.mag << "," << v.ang * Rad_to_deg << ")";        }        else            os << "Vector object mode is invalid";        return os;    }}

接下来是随机漫步问题:将一个人领到街灯柱下，这个人开始走动，但每一步方向都是随机的，求这个人走到离灯柱50英尺需要多少步。

#include"stdafx.h"#include<iostream>#include<cstdlib>#include<ctime>#include"vect.h"int main(){    using namespace std;    using VECTOR::Vector;    srand(time(0));    double direction;    Vector step;    Vector result(0.0, 0.0);    unsigned long steps = 0;    double target;    double dstep;    cout << "Enter target distance (q to quit): ";    while (cin >> target)    {        cout << "Enter target step length: ";        if (!(cin >> dstep))            break;        while (result.magval() < target)        {            direction = rand() % 360;            step.reset(dstep, direction, Vector::POL);            result = result + step;            steps++;        }        cout << "After " << steps << " steps,the subject "            "has the following location:\n";        cout << result << endl;        result.polar_mode();        cout << " or\n" << result << endl;        cout << " Average outward distance per step = ";        cout << result.magval() / steps << endl;        steps = 0;        result.reset(0.0, 0.0);        cout << "Enter target distance (q to quit): ";    }    cout << "Bye!\n";    cin.clear();    while (cin.get() != '\n')        continue;    return 0;}