【C++ Primer Plus】编程练习答案——第15章
1 // chapter15_1_tvremote.h 2 3 #ifndef LEARN_CPP_CHAPTER15_1_TVREMOTE_H 4 #define LEARN_CPP_CHAPTER15_1_TVREMOTE_H 5 class Remote; 6 class Tv { 7 private: 8 int state; 9 int volume; 10 int maxchannel; 11 int channel; 12 int mode; 13 int input; 14 public: 15 friend class Remote; 16 enum {OFF, ON}; 17 enum {MinVal, MaxVal = 20}; 18 enum {Antenna, Cable}; 19 enum {TV, DVD}; 20 21 Tv(int s = OFF, int mc = 125) : state(s), volume(5), maxchannel(mc), channel(2), mode(Cable), input(TV) {} 22 void onoff() {state = (state == ON)? OFF : ON;} 23 bool ison() const {return state == ON;} 24 bool volup(); 25 bool voldown(); 26 void chanup(); 27 void chandown(); 28 void set_mode() {mode = (mode == Antenna)? Cable : Antenna;} 29 void set_input() {input = (input == TV)? DVD : TV;} 30 void settings() const; 31 void set_status(Remote & r); 32 }; 33 34 class Remote { 35 private: 36 int mode; 37 int status; // 常规还是互动模式 38 public: 39 friend class Tv; 40 enum {Normal, Interacte}; 41 42 Remote(int m = Tv::TV) : mode(m), status(Normal){} 43 bool volup(Tv & t) {return t.volup();} 44 bool voldown(Tv & t) {return t.voldown();} 45 void onoff(Tv & t) {t.onoff();} 46 void chanup(Tv & t) {t.chanup();} 47 void chandown(Tv & t) {t.chandown();} 48 void set_chan(Tv & t, int c) {t.channel = c;} 49 void set_input(Tv & t) {t.set_input();} 50 void showstatus() const; 51 }; 52 53 54 #endif //LEARN_CPP_CHAPTER15_1_TVREMOTE_H 55 56 57 // chapter15_1_tvremote.cpp 58 59 #include "chapter15_1_tvremote.h" 60 #include <iostream> 61 62 bool Tv::volup() { 63 if (volume < MaxVal) { 64 ++ volume; 65 return true; 66 } 67 return false; 68 } 69 70 bool Tv::voldown() { 71 if (volume > MinVal) { 72 -- volume; 73 return true; 74 } 75 return false; 76 } 77 78 void Tv::chanup() { 79 if (channel < maxchannel) 80 ++ channel; 81 else 82 channel = 1; 83 } 84 85 void Tv::chandown() { 86 if (channel > 1) 87 -- channel; 88 else 89 channel = maxchannel; 90 } 91 92 void Tv::settings() const { 93 using namespace std; 94 cout << "TV is " << (state == OFF? "OFF" : "ON") << endl; 95 if (state == ON) { 96 cout << "volume setting = " << volume << endl; 97 cout << "channel setting = " << channel << endl; 98 cout << "mode = " << (mode == Antenna? "antenna" : "cable") << endl; 99 cout << "input = " << (input == TV? "TV" : "DVD") << endl; 100 } 101 } 102 103 void Tv::set_status(Remote &r) { 104 if (state == ON) 105 r.status = r.status == Remote::Interacte? Remote::Normal : Remote::Interacte; 106 } 107 108 void Remote::showstatus() const { 109 using namespace std; 110 cout << "status = " << (status == Interacte? "Interacte" : "Normal") << endl; 111 } 112 113 // run 114 115 void ch15_1() { 116 using namespace std; 117 Tv s42; 118 cout << "Initial settings for 42\" TV:\n"; 119 s42.settings(); 120 s42.onoff(); 121 s42.chanup(); 122 s42.chanup(); 123 cout << "\nAdjusted settings for 42\" TV:\n"; 124 s42.settings(); 125 126 Remote grey; 127 grey.set_chan(s42, 10); 128 grey.volup(s42); 129 grey.volup(s42); 130 cout << "\n42\" settings after using remote:\n"; 131 s42.settings(); 132 133 Tv s58(Tv::ON); 134 s58.set_mode(); 135 grey.set_chan(s58, 28); 136 cout << "\n58\" settings:\n"; 137 s58.settings(); 138 139 cout << "\n58\" status:\n"; 140 grey.showstatus(); 141 s58.set_status(grey); 142 grey.showstatus(); 143 }
1 // chapter15_2_stdexcept.h 2 3 #ifndef LEARN_CPP_CHAPTER15_2_STDEXCEPT_H 4 #define LEARN_CPP_CHAPTER15_2_STDEXCEPT_H 5 6 #include <stdexcept> 7 #include <cmath> 8 9 class meanlogicerr : public std::logic_error { 10 public: 11 meanlogicerr() : logic_error("") {} 12 const char * what() {return "bad arguments to hmean() or gmean()";} 13 }; 14 15 #endif //LEARN_CPP_CHAPTER15_2_STDEXCEPT_H 16 17 // run 18 19 double hmean(double a, double b) { 20 if (a == b) 21 throw meanlogicerr(); 22 return 2.0 * a * b / (a + b); 23 } 24 25 double gmean(double a, double b) { 26 if (a < 0 || b < 0) 27 throw meanlogicerr(); 28 return std::sqrt(a * b); 29 } 30 31 void ch15_2() { 32 using namespace std; 33 try {cout << "x = 1, y = 1, hmean = " << hmean(1, 1) << endl;} 34 catch (meanlogicerr & me) {cout << me.what() << endl;} 35 try {cout << "x = -1, y = 1, gmean = " << gmean(-1, 1) << endl;} 36 catch (meanlogicerr & me) {cout << me.what() << endl;} 37 try {cout << "x = 1, y = 2, hmean = " << hmean(1, 2) << endl;} 38 catch (meanlogicerr & me) {cout << me.what() << endl;} 39 try {cout << "x = 1, y = 1, gmean = " << gmean(1, 1) << endl;} 40 catch (meanlogicerr & me) {cout << me.what() << endl;} 41 }
1 // chapter15_3_meanerr.h 2 3 #ifndef LEARN_CPP_CHAPTER15_3_MEANERR_H 4 #define LEARN_CPP_CHAPTER15_3_MEANERR_H 5 6 #include <stdexcept> 7 #include <iostream> 8 #include <string> 9 10 class twodouargserr : public std::logic_error { 11 private: 12 double arg1; 13 double arg2; 14 std::string funcname; 15 public: 16 twodouargserr(double a1 = 0, double a2 = 0, const char * f = "none") 17 : arg1(a1), arg2(a2), funcname(f), std::logic_error("") {} 18 virtual const char * what() {return "invalid args";} 19 virtual void msg(){std::cout << funcname << "() logicerr, arg1: " << arg1 << " arg2: " << arg2 << std::endl;} 20 }; 21 22 class hmean_err : public twodouargserr { 23 public: 24 hmean_err(double a1 = 0, double a2 = 0, const char * f = "none") 25 : twodouargserr(a1, a2, f) {} 26 virtual const char * what() {return "invalid args";} 27 virtual void msg(){twodouargserr::msg();} 28 }; 29 30 class gmean_err : public twodouargserr { 31 public: 32 gmean_err(double a1 = 0, double a2 = 0, const char * f = "none") 33 : twodouargserr(a1, a2, f) {} 34 virtual const char * what() {return "invalid args";} 35 virtual void msg(){twodouargserr::msg();} 36 }; 37 38 39 #endif //LEARN_CPP_CHAPTER15_3_MEANERR_H 40 41 // run 42 43 double hmean2(double a, double b) { 44 if (a == b) 45 throw hmean_err(a, b, __func__ ); 46 return 2.0 * a * b / (a + b); 47 } 48 49 double gmean2(double a, double b) { 50 if (a < 0 || b < 0) 51 throw gmean_err(a, b, __func__ ); 52 return std::sqrt(a * b); 53 } 54 void ch15_3() { 55 using namespace std; 56 try {cout << "x = 1, y = 1, hmean = " << hmean2(1, 1) << endl;} 57 catch (hmean_err & he) {cout << he.what() << endl; he.msg();} 58 try {cout << "x = 1, y = 2, hmean = " << hmean2(1, 2) << endl;} 59 catch (hmean_err & he) {cout << he.what() << endl; he.msg();} 60 try {cout << "x = -1, y = 1, gmean = " << gmean2(-1, 1) << endl;} 61 catch (gmean_err & ge) {cout << ge.what() << endl; ge.msg();} 62 try {cout << "x = 1, y = 1, hmean = " << gmean2(1, 1) << endl;} 63 catch (gmean_err & ge) {cout << ge.what() << endl; ge.msg();} 64 }
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