【C++ Primer Plus习题】11.1

news2024/11/15 17:55:16

问题:

解答:
main.cpp

#include <iostream>
#include <fstream>
#include "Vector.h"
#include <time.h>
using namespace std;
using namespace VECTOR;

int main()
{
	ofstream fout;
	fout.open("randwalk.txt");
	srand(time(0));

	double direction;
	Vector step;
	Vector result(0.0, 0.0);
	unsigned long steps = 0;
	double target;
	double dstep;
	cout << "请输入目标距离(q结束):";
	while (cin>>target&&cin.get()!='q')
	{
		cout << "请输入步长:";
		if (!(cin >> dstep))
			break;
		fout << "目标距离: " << target << ", 步长: " << dstep << endl;

		while (result.magval()<target)
		{
			fout << steps << " : " << result << endl;
			direction = rand() % 360;
			step.reset(dstep, direction, Vector::POL);
			result =result+step;
			steps++;
		}
		cout << "经过 " << steps << "步,实验对象的位置如下:\n";
		cout << result << endl;

		fout << "经过 " << steps << "步,实验对象的位置如下:\n";
		fout << result << endl;
		result.polar_mode();
		cout << " 或者\n" << result << endl;
		cout << "每一步向外的平均距离 = " << result.magval() / steps << endl;

		fout << " 或者\n" << result << endl;
		fout << "每一步向外的平均距离 = " << result.magval() / steps << endl;

		steps = 0;
		result.reset(0.0, 0.0);
		cout << "请输入目标距离(q结束):";
	}
	cout << "Bye!\n";
	fout.close();

	return 0;
}

Vector.h

#pragma once
#include <iostream>
using namespace std;

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 from = 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 ostream& operator<<(ostream& os, const Vector& v);
	};

}

Vector.cpp

#include "Vector.h"
#include <cmath>

namespace VECTOR
{
	const double Rad_to_deg = 45.0 / atan(1.0);//45/(π/4)


	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 (mode == RECT)
		{
			x = n1;
			y = n2;
			set_mag();
			set_ang();
		}
		else if (mode == POL)
		{
			mag = n1;
			ang = n2 / Rad_to_deg;
			set_x();
			set_y();
		}
		else
		{
			cout << "错误!" << endl;
			x = y = mag = ang = 0.0;
			mode = RECT;
		}
	}
	void Vector::reset(double n1, double n2, Mode from)
	{
		mode = from;
		if (mode == RECT)
		{
			x = n1;
			y = n2;
			set_mag();
			set_ang();
		}
		else if (mode == POL)
		{
			mag = n1;
			ang = n2 / Rad_to_deg;
			set_x();
			set_y();
		}
		else
		{
			cout << "错误!" << endl;
			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(x * n, y *n);
	}

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

}