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Valarray类

模板类

格式：

基本函数：

程序示例：

studentc.h 奇怪 为毛没有彩色

#ifndef STUDENTC_H_#define STUDENTC_H_#include 
   
    #include 
    
     #include 
     
      class Student{  private:    typedef std::valarray
      
        ArrayDb;    std::string name;    ArrayDb scores;    std::ostream & arr_out(std::ostream & os) const;  public:    Student() : name("Null Student"), scores() {}    explicit Student(const std::string & s) : name(s), scores() {}    explicit Student(int n) : name("Nully"), scores(n) {}    Student(const std::string & s, int n) : name(s), scores(n) {}    Student(const std::string & s, const ArrayDb & a) : name(s), scores(a) {}    Student(const char* str, const double* pd, int n) : name(str), scores(pd, n) {}    ~Student() {}    double Average() const;    const std::string & Name() const;    double & operator[] (int i);    double operator[] (int i) const;    friend std::istream & operator >> (std::istream & is, Student & stu);    friend std::istream & getline(std::istream & is, Student & stu);    friend std::ostream & operator << (std::ostream & os, const Student & stu);};#endif
      
     
    
   

student.cpp

#include "studentc.h"using std::ostream;using std::endl;using std::istream;using std::string;double Student::Average() const{  if (scores.size() > 0)    return scores.sum() / scores.size();  else    return 0;}const string & Student::Name() const{  return name;}double & Student::operator[](int i){  return scores[i];}double Student::operator[](int i) const{  return scores[i];}ostream & Student::arr_out(ostream & os) const{  int i;  int lim = scores.size();  if (lim > 0)  {    for (i = 0; i < lim; i++)    {      os << scores[i] << " ";      if (i % 5 == 4)        os <
   
    >(istream & is, Student & stu){  is >> stu.name;  return is;}istream & getline(istream & is, Student & stu){  getline(is, stu.name);  return is;}ostream & operator<<(ostream & os, const Student & stu){  os << "Scores for " << stu.name << ":\n";  stu.arr_out(os);  return os;}
   

use_stuc.cpp

#include 
   
    #include "studentc.h"using std::cout;using std::cin;using std::endl;void set(Student & sa, int n);const int pupils = 3;const int quizzes = 5;int main(){  Student ada[pupils] =    {Student(quizzes), Student(quizzes), Student(quizzes)};  int i;  for (i = 0; i < pupils; ++i)    set(ada[i], quizzes);  cout << "\nResults:";  for ( i = 0; i < pupils; ++i)  {    cout << endl << ada[i];    cout << "average: " << ada[i].Average() <
    
     > sa[i];  while (cin.get() != '\n')    continue;}
    
   

运行结果

私有继承：

私有继承与包含的区别：

如果需要调用基类的对象咋搞？

在私有继承中，在没有显式类型转换的情况下，不能将指向派生类的对象或引用赋给基类引用或指针

还有一种情况是 多重继承 编译器无法确定要转换成哪个基类 因为都有operator<<()

私有继承的程序示例：

studenti.h

#ifndef STUDENTC_H_#define STUDENTC_H_#include 
   
    #include 
    
     #include 
     
      class Student : private std::string, private std::valarray
      
       {  private:    typedef std::valarray
       
         ArrayDb;    std::ostream & arr_out(std::ostream & os) const;  public:    Student() : std::string("Null Student"), ArrayDb() {}    explicit Student(const std::string & s) : std::string(s), ArrayDb() {}    explicit Student(int n) : std::string("Nully"), ArrayDb(n) {}    Student(const std::string & s, int n) : std::string(s), ArrayDb(n) {}    Student(const std::string & s, const ArrayDb & a) : std::string(s), ArrayDb(a) {}    Student(const char* str, const double* pd, int n) : std::string(str), ArrayDb(pd, n) {}    ~Student() {}    double Average() const;    const std::string & Name() const;    double & operator[] (int i);    double operator[] (int i) const;    friend std::istream & operator >> (std::istream & is, Student & stu);    friend std::istream & getline(std::istream & is, Student & stu);    friend std::ostream & operator << (std::ostream & os, const Student & stu);};#endif
       
      
     
    
   

studenti.cpp

#include "studenti.h"using std::ostream;using std::endl;using std::istream;using std::string;double Student::Average() const{  if (ArrayDb::size() > 0)    return ArrayDb::sum() / ArrayDb::size();  else    return 0;}const string & Student::Name() const{  return (const string &) *this;}double & Student::operator[](int i){  return ArrayDb::operator[](i);}double Student::operator[](int i) const{  return ArrayDb::operator[](i);}ostream & Student::arr_out(ostream & os) const{  int i;  int lim = ArrayDb::size();  if (lim > 0)  {    for (i = 0; i < lim; i++)    {      os << ArrayDb::operator[](i) << " ";      if (i % 5 == 4)        os <
   
    >(istream & is, Student & stu){  is >> (string &) stu;  return is;}istream & getline(istream & is, Student & stu){  getline(is, (string &) stu);  return is;}ostream & operator<<(ostream & os, const Student & stu){  os << "Scores for " << (string &) stu << ":\n";  stu.arr_out(os);  return os;}
   

use_stui.cpp

#include 
   
    #include "studenti.h"using std::cout;using std::cin;using std::endl;void set(Student & sa, int n);const int pupils = 3;const int quizzes = 5;int main(){  Student ada[pupils] =    {Student(quizzes), Student(quizzes), Student(quizzes)};  int i;  for (i = 0; i < pupils; ++i)    set(ada[i], quizzes);  cout << "\nResults:";  for ( i = 0; i < pupils; ++i)  {    cout << endl << ada[i];    cout << "average: " << ada[i].Average() <
    
     > sa[i];  while (cin.get() != '\n')    continue;}
    
   

用包含还是用私有继承？

完结 

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