C++Primer Plus筆記——第十五章 友元、異常和其他課後程式設計練習答案
阿新 • • 發佈：2018-12-13
課後程式設計練習答案
習題1 習題2 習題3 習題4
習題1
//tv.h #ifndef TV_H_ #define TV_H_ #include <iostream> using namespace std; class Tv { friend class Remote; public: enum { Off, On }; enum { MinVal, MaxVal = 20 }; enum { Antenna, Cable }; enum { TV, DVD }; enum { USUAL, EXCHANGE }; Tv(int s = Off, int mc = 125) :state(s), volume(5), maxchannel(mc), channel(2), mode(Cable), input(TV) {} ~Tv() {} void onoff() { state = (state == On) ? Off : On; } bool ison()const { return state == On; } bool volup(); bool voldown(); void chanup(); void chandown(); void set_mode() { mode = (mode == Antenna) ? Cable : Antenna; } void set_input() { input = (input == TV) ? DVD : TV; } void settings() const; void set_rmode(Remote &r); private: int state; int volume; int maxchannel; int channel; int mode; int input; }; class Remote { private: friend class Tv; enum { USUAL, EXCHANGE }; int mode; int fmode; public: Remote(int m = Tv::TV, int f = USUAL) :mode(m), fmode(f) {} bool volup(Tv&t) { return t.volup(); } bool voldown(Tv&t) { return t.voldown(); } void onoff(Tv&t) { t.onoff(); } 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 set_input(Tv&t) { t.set_input(); } void mode_show()const { cout << "Remote pretent mode is " << fmode << endl; } }; inline void Tv::set_rmode(Remote &r) { if (ison()) { r.fmode = Remote::EXCHANGE; r.mode_show(); } } #endif
//tvfm.h #ifndef TVFM_H_ #define TVFM_H_ #include <iostream> using namespace std; class Tv; class Remote { public: enum State { Off, On }; enum { MinVal, MaxVal = 20 }; enum { Antenna, Cable }; enum { TV, DVD }; private: int mode; public: Remote(int m = TV) :mode(m) {} bool volup(Tv&t); bool voldown(Tv&t); void onoff(Tv&t); void chanup(Tv&t); void chandown(Tv&t); void set_chan(Tv&t, int c); void set_mode(Tv&t); void set_input(Tv&t); }; class Tv { public: friend void Remote::set_chan(Tv&t, int c); enum State { Off, On }; enum { MinVal, MaxVal = 20 }; enum { Antenna, Cable }; enum { TV, DVD }; Tv(int s = Off, int mc = 125) :state(s), volume(5), maxchannel(mc), channel(2), mode(Cable), input(TV) {} ~Tv() {} void onoff() { state = (state == On) ? Off : On; } bool ison()const { return state == On; } bool volup(); bool voldown(); void chanup(); void chandown(); void set_mode() { mode = (mode == Antenna) ? Cable : Antenna; } void set_input() { input = (input == TV) ? DVD : TV; } void settings()const; private: int state; int volume; int maxchannel; int channel; int mode; int input; }; inline bool Remote::volup(Tv&t) { return t.volup(); } inline bool Remote::voldown(Tv&t) { return t.voldown(); } inline void Remote::onoff(Tv&t) { t.onoff(); } inline void Remote::chanup(Tv&t) { t.chanup(); } inline void Remote::chandown(Tv&t) { t.chandown(); } inline void Remote::set_chan(Tv&t, int c) { t.channel = c; } inline void Remote::set_mode(Tv&t) { t.set_mode(); } inline void Remote::set_input(Tv&t) { t.set_input(); } #endif
//tv.cpp #include "tv.h" //#include "tvfm.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; } void Tv::chandown() { if (channel > 1) channel--; else channel = maxchannel; } void Tv::settings()const { 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 << "Input = " << (input == TV ? "TV" : "DVD") << endl; } }
//use_tv.cpp
#include "tv.h"
int main()
{
Tv s42;
Remote grey;
grey.mode_show();
cout << "Initial settings for 42\" TV:\n";
s42.settings();
s42.onoff();
s42.chanup();
cout << "\nAdjusted settings for 42\" TV:\n";
s42.settings();
s42.set_rmode(grey);
grey.set_chan(s42, 10);
grey.volup(s42);
grey.volup(s42);
cout << "\n42\" settings after using remote:\n";
s42.settings();
Tv s58(Tv::On);
s58.set_mode();
grey.set_chan(s58, 28);
cout << "\n58\" settings:\n";
s58.settings();
s58.set_rmode(grey);
system("pause");
return 0;
}習題2
//exc_mean.h
#ifndef EXC_MEAN_H_
#define EXC_MEAN_H_
#include <iostream>
#include <cmath>
#include <stdexcept>
#include <string>
using namespace std;
class bad_hmean :public logic_error
{
private:
string name;
public:
explicit bad_hmean(const string &n = "hmean", const string &s = "Error in hmean()\n");
string mesg();
virtual ~bad_hmean() throw() {}
};
bad_hmean::bad_hmean(const string &n, const string &s) :name(n), logic_error(s) { }
inline string bad_hmean::mesg()
{
return "hmean() arguments a=-b should be div a+b=0!\n";
}
class bad_gmean :public logic_error
{
private:
string name;
public:
explicitbad_gmean(const string &n = "gmean", const string &s = "Error in gmean()\n");
stringmesg();
virtual ~bad_gmean()throw() {}
};
bad_gmean::bad_gmean(const string &n, const string &s) :name(n), logic_error(s) { }
inline string bad_gmean::mesg()
{
return "gmean() arguments should be >= 0\n";
}
#endif//error.cpp
#include "exc_mean.h"
double hmean(double a, double b);
double gmean(double a, double b);
int main()
{
double x, y, z;
cout << "Enter two numbers:";
while (cin >> x >> y)
{
try {
z = hmean(x, y);
cout << "Harmonic mean of " << x << " and " << y
<< " is " << z << endl;
cout << "Geomettric mean of " << x << " and " << y
<< " is " << gmean(x, y) << endl;
cout << "Enter next set of numbers <q to quit>: ";
}
catch (bad_hmean&bg)
{
cout << bg.what();
cout << "Error message: \n" << bg.mesg() << endl;
cout << "Try again.\n";
continue;
}
catch (bad_gmean&hg)
{
cout << hg.what();
cout << "Error message: \n" << hg.mesg() << endl;
cout << "Sorry, you don't get to play and more.\n";
break;
}
}
cout << "Bye!\n";
system("pause");
return 0;
}
double hmean(double a, double b)
{
if (a == -b)
throw bad_hmean();
return 2.0*a*b / (a + b);
}
double gmean(double a, double b)
{
if (a < 0 || b < 0)
throw bad_gmean();
return sqrt(a*b);
}習題3
#ifndef EXC_MEAN_H_
#define EXC_MEAN_H_
#include <iostream>
#include <cmath>
#include <stdexcept>
#include <string>
using namespace std;
class bad_hmean :public logic_error
{
private:
string name;
public:
double v1;
double v2;
explicitbad_hmean(double a = 0, double b = 0,
const string &s = "Error in hmean()\n");
voidmesg();
virtual ~bad_hmean()throw() {}
};
bad_hmean::bad_hmean(double a, double b, const string &s):v1(a), v2(b), logic_error(s)
{
name = "hmean";
}
inline void bad_hmean::mesg()
{
cout << name << "(" << v1 << ", " << v2 << ") arguments a=-b should be div a+b=0!\n";
}
class bad_gmean :public bad_hmean
{
private:
string name;
public:
explicitbad_gmean(double a = 0, double b = 0,
const string &s = "Error in gmean()\n");
voidmesg();
virtual ~bad_gmean()throw() {}
};
bad_gmean::bad_gmean(double a, double b, const string &s):bad_hmean(a, b, s)
{
name = "gmean";
}
inline void bad_gmean::mesg()
{
cout << name << "(" << bad_hmean::v1 << ", " << bad_hmean::v2 << ") arguments should be >= 0\n";
}
#endif
//error.cpp
#include "exc_mean.h"
double hmean(double a, double b);
double gmean(double a, double b);
int main()
{
double x, y, z;
cout << "Enter two numbers:";
while (cin >> x >> y)
{
try {
z = hmean(x, y);
cout << "Harmonic mean of " << x << " and " << y
<< " is " << z << endl;
cout << "Geomettric mean of " << x << " and " << y
<< " is " << gmean(x, y) << endl;
cout << "Enter next set of numbers <q to quit>: ";
}
catch (bad_gmean&hg)
{
cout << hg.what();
cout << "Error message: \n";
hg.mesg();
cout << endl;
cout << "Sorry, you don't get to play and more.\n";
break;
}
catch (bad_hmean&bg)
{
cout << bg.what();
cout << "Error message: \n";
bg.mesg();
cout << endl;
cout << "Try again.\n";
continue;
}
}
cout << "Bye!\n";
system("pause");
return 0;
}
doublehmean(double a, double b)
{
if (a == -b)
throw bad_hmean();
return 2.0*a*b / (a + b);
}
doublegmean(double a, double b)
{
if (a < 0 || b < 0)
throw bad_gmean();
return sqrt(a*b);
}習題4
//sales.h
#ifndef SALES_H_
#define SALES_H_
#include <stdexcept>
#include <string>
#include <cstring>
#include <iostream>
#include <cstdlib>
using namespace std;
class Sales
{
public:
enum { MONTHS = 12 };
class bad_index :public logic_error
{
private:
int bi;
public:
explicit bad_index(int ix, const string &s = "Index error in Sales object\n");
int bi_val()const { return bi; }
virtual ~bad_index()throw() {}
};
explicit Sales(int yy = 0);
Sales(int yy, const double *gr, int n);
virtual ~Sales() {}
int Year()const { return year; }
virtual double operator[](int i)const;
virtual double &operator[](int i);
private:
double gross[MONTHS];
int year;
};
class LabeledSales :public Sales
{
public:
class nbad_index : public Sales::bad_index
{
private:
std::string lbl;
public:
nbad_index(const string &lb, int ix,
const string &s = "Index error in LabeledSales object\n");
const string &label_val()const { return lbl; }
virtual ~nbad_index()throw() {}
};
explicit LabeledSales(const string &lb = "none", int yy = 0);
LabeledSales(const string &lb, int yy, const double *gr, int n);
virtual ~LabeledSales() {}
const string &Label()const { return label; }
virtual double operator[](int i)const;
virtual double &operator[](int i);
private:
string label;
};
#endif//sales.cpp
#include "sales.h"
Sales::bad_index::bad_index(int ix,
const string &s) :logic_error(s), bi(ix)
{
}
Sales::Sales(int yy)
{
year = yy;
for (int i = 0; i < MONTHS; ++i)
gross[i] = 0;
}
Sales::Sales(int yy, const double *gr, int n)
{
year = yy;
int lim = (n < MONTHS) ? n : MONTHS;
int i;
for (i = 0; i < lim; ++i)
gross[i] = gr[i];
for (; i < MONTHS; ++i)
gross[i] = 0;
}
double Sales::operator[](int i)const
{
if (i < 0 || i >= MONTHS)
throw bad_index(i);
return gross[i];
}
double&Sales::operator[](int i)
{
if (i < 0 || i >= MONTHS)
throw bad_index(i);
return gross[i];
}
LabeledSales::nbad_index::nbad_index(const string &lb, int ix,
const string &s) :Sales::bad_index(ix, s)
{
lbl = lb;
}
LabeledSales::LabeledSales(const string &lb, int yy) : Sales(yy)
{
label = lb;
}
LabeledSales::LabeledSales(const string &lb, int yy, const double *gr, int n) : Sales(yy, gr, n)
{
label = lb;
}
double LabeledSales::operator[](int i)const
{
if (i < 0 || i >= MONTHS)
throw nbad_index(Label(), i);
return Sales::operator[](i);
}
double&LabeledSales::operator[](int i)
{
if (i < 0 || i >= MONTHS)
throw nbad_index(Label(), i);
return Sales::operator[](i);
}//use_sales.cpp
#include "sales.h"
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, 24,
28, 29, 33, 29, 32, 35
};
Sales sales1(2011, vals1, 12);
LabeledSales sales2("Blogstar", 2012, vals2, 12);
Sales::bad_index *s;
LabeledSales::nbad_index *l;
cout << "First try block:\n";
try
{
int i;
cout << "Year = " << sales1.Year() << endl;
for (i = 0; i < 12; ++i)
{
cout << sales1[i] << ' ';
if (i % 6 == 5)
cout << endl;
}
cout << "Year = " << sales2.Year() << endl;
cout << "Label = " << sales2.Label() << endl;
for (i = 0; i <= 12; ++i)
{
cout << sales2[i] << ' ';
if (i % 6 == 5)
cout << endl;
}
cout << "End of try block 1.\n";
}
catch (logic_error&bad)
{
cout << bad.what();
if (l = dynamic_cast<LabeledSales::nbad_index *>(&bad))
{
cout << "Comany: " << l->label_val() << endl;
cout << "bad index: " << l->bi_val() << endl;
}
else if (s = dynamic_cast<Sales::bad_index *>(&bad))
cout << "bad index: " << s->bi_val() << endl;
}
cout << "\nNext try block:\n";
try
{
sales2[2] = 37.5;
sales1[20] = 23345;
cout << "End of try block 2.\n";
}
catch (logic_error&bad)
{
cout << bad.what();
if (l = dynamic_cast<LabeledSales::nbad_index *>(&bad))
{
cout << "Comany: " << l->label_val() << endl;
cout << "bad index: " << l->bi_val() << endl;
}
else if (s = dynamic_cast<Sales::bad_index *>(&bad))
cout << "bad index: " << s->bi_val() << endl;
}
cout << "done\n";
system("pause");
return 0;
}