c++ Primer Plus（第六版）第十⑤章習題，寫代碼之路

2019-11-10 16:58:12

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c++ PRimer Plus（習題15.1)

//對書上的友元類進行成員的增加// 一種簡單的修改#include<iostream>#include"tv.h"int main(){	using std::cout;	Tv s42;	cout << "Initial settings for 42: /n";	s42.settings();	s42.onoOff();	cout << "/nAffter settinfs: /n ";	s42.settings();	Remote grey;	grey.chanup(s42);	grey.volup(s42);	s42.set_style(grey);	cout << "/nAffter setting: /n";	s42.settings();	grey.showstyle();	return 0;}#pragma once#pragma execution_character_set("utf-8")//本文件為utf-8編碼格式//書上的友元類的程序清單，順便做15.1題目，增加一個成員#ifndef TV_H#define TV_Hclass Tv{public:	friend class Remote;				//友元類就是這樣玩的	enum {Off,On};						//電視開關			enum { MinVal, MaxVal=20 };			//聲音大小	enum { Antenna, Cable };			//有線電視或者是天線	enum{TV,DVD};						//兩種模式		Tv(int s=Off,int mc=125):state(s),volume(5),		maxchannel(mc),channel(5),mode(Cable),input(TV){}	//默認構造函數	void onoOff() { state ^= 1; }				//切換模式，按位異或	bool ison()const { return state == On; }		//檢查電視是否打開的方法	bool volup();								//調整音量的方法	bool voldown();	void chanup();								//調整頻道的方法	void chandown();	void set_style(Remote &r);	//調整互動模式或者是常規模式的方法	void set_mode() { mode ^= 1; }	void set_input() { input ^= 1; }	void settings()const;private:	int state;	int volume;	int maxchannel;	int channel;	int mode;	int input;};class Remote{private:	int mode;	int style;public:	friend class Tv;				//讓他們互相成為友元，Tv才能使用更改,Romote的style成員	enum { Normal, Action };	Remote(int m = Tv::TV):mode(m),style(Normal) {};	bool volup(Tv&t) { return t.volup(); };			//括號外面可以不加冒號	bool voldown(Tv&t) { return t.voldown(); };	void onoff(Tv&t) { t.onoOff(); }	void chanup(Tv&t) { t.chanup(); }	void chandown(Tv&t) { t.chandown(); }	void set_chan(Tv&t, int c) { t.channel = c; }	void set_mode(Tv&t) { t.set_mode(); }	void showstyle()const;};#endif // !TV_H//tv頭文件的實現方法#include<iostream>#include"tv.h"bool Tv::volup(){	if (volume <MaxVal)	{		volume++;		return true;	}	else		return false;}bool Tv::voldown(){	if (volume > MinVal)	{		volume--;		return true;	}	else		return false;}void Tv::chanup(){	if (channel < maxchannel)		channel++;	else		channel = 1;			//頻道調整是設置成循環，當到達最大值，重新設置為第一個頻道}void Tv::chandown(){	if (channel > 1)		channel--;	else		channel = maxchannel;}void Tv::settings()const{	using std::cout;	using std::endl;	cout << "TV is " << (state == Off ? "Off" : "On") << endl;	if (state == On)	{		cout << "Volume setting = " << volume << endl;		cout << "Channel setting = " << channel << endl;		cout << "Mode = "			<< (mode == Antenna ? "antenna" : "cable") << endl;		cout << "Iuput = "			<< (input == TV ? "TV" : "DVD") << endl;	}}void Tv::set_style(Remote&r){	if (state == 1)		r.style ^= 1;	//接受的是一個遙控器對象，竟然無法更改私有成員}void Remote::showstyle()const{	std::cout << "Style = "		<< (style==Normal?"Normal":"Action")<< std::endl;}c++ Primer Plus（習題15.2)
//派生一個異常類以excception派生//并修改程序清單15.11，讓what方法報告錯誤的函數名和問題性質#include<iostream>#include<exception>class bad_hmean :public std::exception				//Hanomic error class{private:	double v1;	double v2;public:	const char* what() 	{ return "bad argument to hmean(),invalid argument:a=-b/n"; }	bad_hmean(double a = 0, double b = 0) :v1(a), v2(b) {};};class bad_gmean :public std::exception				//Geometric error class{private:	double v1;	double v2;public:	const char* what() { return "bad argument to gmean(),argument shoule be >=0/n"; }	bad_gmean(double a = 0, double b = 0) :v1(a), v2(b) {};};double hmean(double a, double b);double gmean(double a, double b);int main(){	using std::cout;	using std::cin;	using std::endl;	double x, y, z;	cout << "Enter two numbers: ";	while (cin >> x >> y)	{		try		{			z = hmean(x, y);			cout << "Hanomic mean of " << x << " and " << y << " is " << z << endl;			cout << "Geometric mean of " << x << " and " << y << " is " << gmean(x, y) << endl;			cout << "Enter the next set of numbers<q to exit>";		}//使用try塊		catch (bad_gmean&bg)					//捕捉異常輸入		{			cout<<bg.what();			cout << "Try again./n";			continue;		}		catch (bad_hmean&hg)					//捕捉異常輸入		{			cout<<hg.what();			cout << "Sorry,you don't get to play any more./n";			break;		}	}		cout << "Bye!/n";		return 0;	}	double hmean(double a, double b)	{		if (a == -b)			throw bad_hmean(a, b);		return 2.0*a*b / (a + b);	}	double gmean(double a, double b)	{		if (a<0||b<0)			throw bad_gmean(a, b);		return std::sqrt(a*b);	}c++ Primer Plus（習題15.3)
//這題跟前面那題差不多，不過要從一個異常基類中派生出來//這樣就具有多態性，根據錯類型來調用方法//并修改程序清單15.11，讓what方法報告錯誤的函數名和問題性質#include<iostream>class logic_error{protected:	double v1;	double v2;public:	logic_error(double a = 0, double b = 0) :v1(a), v2(b) {};	virtual void Report() {};		//虛函數,花括號必須的，不然vs2015鏈接錯誤};class bad_hmean:public logic_error			//Hanomic error class{public:	virtual void Report()	{		std::cout << "bad argument to hmean(),invalid argument:a=-b/n"			<< "You input " << logic_error::v1 << "=" << logic_error::v2 << std::endl;	}	bad_hmean(double a = 0, double b = 0) :logic_error(a,b) {};};class bad_gmean :public logic_error			//Geometric error class{public:	virtual void Report()	{ 		std::cout<<"bad argument to gmean(),argument shoule be >=0/n"			<< "You input " << logic_error::v1 << " or " << logic_error::v2 <<" <0"<< std::endl;	}	bad_gmean(double a = 0, double b = 0) :logic_error(a,b)  {};};double hmean(double a, double b);double gmean(double a, double b);int main(){	using std::cout;	using std::cin;	using std::endl;	double x, y, z;	cout << "Enter two numbers: ";	while (cin >> x >> y)	{		try		{			z = hmean(x, y);			cout << "Hanomic mean of " << x << " and " << y << " is " << z << endl;			cout << "Geometric mean of " << x << " and " << y << " is " << gmean(x, y) << endl;			cout << "Enter the next set of numbers<q to exit>";		}//使用try塊		catch (logic_error&hg)					//捕捉異常輸入		{			hg.Report();			cout << "Sorry,you don't get to play any more./n";			break;		}	}	cout << "Bye!/n";	return 0;}double hmean(double a, double b){	if (a == -b)		throw bad_hmean(a, b);	return 2.0*a*b / (a + b);}double gmean(double a, double b){	if (a<0 || b<0)		throw bad_gmean(a, b);	return std::sqrt(a*b);}c++ Primer Plus（習題15.4)//這題修改書上的代碼，這總比自己寫容易點，不過還是要打代碼//省不了的事，修改程序用一個catch來捕捉非法索引錯誤//而且要使用RTTI運行階段類型識別的特性//說白了還是類的多態性，看需要調用哪個類的方法#include "sales.h"  #include <iostream>  int main(){	double vals1[12] =	{		1220, 1100, 1122, 2212, 1232, 2334,		2884, 2393, 3302, 2922, 3002, 3544	};	double vals2[12] =	{		12, 11, 22, 21, 32, 34,		28, 29, 33, 29, 32, 35	};	Sales sales1(2011, vals1, 12);	LabeledSales sales2("Blogstar", 2012, vals2, 12);	std::cout << "First try block:/n";	try	{		int i;		std::cout << "Year = " << sales1.Year() << std::endl;		for (i = 0; i < 12; ++i)		{			std::cout << sales1[i] << ' ';			if (i % 6 == 5)				std::cout << std::endl;		}		std::cout << "Year = " << sales2.Year() << std::endl;		std::cout << "Label = " << sales2.Label() << std::endl;		for (i = 0; i <= 12; ++i)		{			std::cout << sales2[i] << ' ';			if (i % 6 == 5)				std::cout << std::endl;		}		std::cout << "End of try block 1./n";	}	catch (std::logic_error &le)		//祖先基類，引用派生類	{		std::cout << le.what();			//what方法接受一個string字符串		if (LabeledSales::nbad_index *ni = dynamic_cast<LabeledSales::nbad_index *>(&le))		{			//看能否安全轉換，意思是多態性			std::cout << "Company: " << ni->label_val() << std::endl;			std::cout << "bad index: " << ni->bi_val() << std::endl;		}		else if (Sales::bad_index *bi = dynamic_cast<Sales::bad_index *>(&le))			std::cout << "bad index: " << bi->bi_val() << std::endl;	}	std::cout << "/nNext try block:/n";	try	{		sales2[2] = 37.5;		sales1[20] = 23345;		std::cout << "End of try block 2./n";	}	catch (std::logic_error &le)	{		//都是這樣改，就這么簡單		std::cout << le.what();		if (LabeledSales::nbad_index *ni = dynamic_cast<LabeledSales::nbad_index *>(&le))		{			std::cout << "Company: " << ni->label_val() << std::endl;			std::cout << "bad index: " << ni->bi_val() << std::endl;		}		else if (Sales::bad_index *bi = dynamic_cast<Sales::bad_index *>(&le))			std::cout << "bad index: " << bi->bi_val() << std::endl;	}	return 0;}