C++ Primer Plus第六版 第十一章 编程练习答案

//第一题
//windows下\r\n在txt中是换行...被坑了= = 话说开学了课好多啊= =....更新的都好迟。。。
//vector.h
#ifndef VECTOR_H_
#define VECTOR_H_

#include <iostream>
namespace VECTOR
{
	class Vector
	{
	public:
		enum Mode { RECT, POL };
	private:
		double x;
		double y;
		double mag;
		double ang;
		Mode mode;
		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();
		Vector operator-(const Vector &b) const;
		Vector operator+(const Vector &b) const;
		Vector operator-() const;
		Vector operator*(double n) const;
		friend Vector operator *(double n, const Vector &a);
		friend std::ostream &operator<<(std::ostream &os, const Vector &v);
	};
}

#endif

//vector.cpp
#include <cmath>
#include "vector.h"
using std::sqrt;
using std::sin;
using std::cos;
using std::atan;
using std::atan2;
using std::cout;

namespace VECTOR
{
	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);
	}

	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;
	}

	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);
	}

	Vector operator*(double n, const Vector &a)
	{
		return a * n;
	}

	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;
	}
}

//main.cpp
#include <iostream>
#include <fstream>
#include <cstdlib>
#include <ctime>
#include "vector.h"

int main()
{
	std::fstream f;
	f.open("result.txt", 'w');
	srand(time(0));
	double direction;
	VECTOR::Vector step;
	VECTOR::Vector result(0.0, 0.0);
	unsigned long steps = 0;
	double target;
	double dstep;
	std::cout << "Enter target distance (q to quit): ";
	while (std::cin >> target)
	{
		std::cout << "Enter step length: ";
		if (!(std::cin >> dstep))
			break;
		f << "Target Distance: " << target << "Step Size: " << dstep << "\r\n";
		while (result.magval() < target)
		{
			direction = rand() % 360;
			step.reset(dstep, direction, VECTOR::Vector::POL);
			result = result + step;
			f << steps << ": (x, y) = (" << step.xval() << ", " << step.yval() << ")\r\n";
			steps++;
		}
		f << "After " << steps << " steps, the subject has the following location:\r\n" << result << "\r\n";
		result.polar_mode();
		f << " or\r\n" << "Average outward distance per step = " << result.magval() / steps << "\r\n";
		steps = 0;
		std::cout << "Enter target distance (q to quit): ";
	}
	f.close();
	std::cout << "Bye!" << std::endl;
	std::cin.clear();
	wh