c++ primer 学习笔记3

包含对象成员的类valarray类是由头文件valarray支持的。

顾名思义，这个类用于处理数值，他支持诸如将数组中的所有元素的值想家以及在数组中找出最大和最小的值等操作。

valarray被定义为一个模板类，以便能够处理不同的数据类型。

一个Student类----一个getline导致构造函数递归的类[cpp]view plaincopyprint?1.// readBook2.cpp : 定义控制台应用程序的入口点。

2.//3.4.#include "stdafx.h"5.#include "iostream"ing namespace std;7.#include "valarray"8.#include "string"9.10.class CStudent11.{12.public:13.typedef std::valarray<double> ArrayDb;14. CStudent() : sz_Name( "Null Student" ), m_ArrScores()15. {16. }17. CStudent( const string& name ) : sz_Name( name), m_ArrScores()18. {19. }20.explicit CStudent( int n ) : sz_Name( "Nully"), m_ArrScores( n )21. {22. }23. CStudent( const string& name, int n ) : sz_Name( name ), m_ArrScores( n )24. {25. }26. CStudent( const string& name, const ArrayDb& a) : sz_Name( name ), m_ArrScores( a )27. {28. }29. CStudent( const char* name, const double* pd,int n ) : sz_Name( name ), m_ArrScores( pd, n )30. {31. }32.double Average() const33. {34.if ( m_ArrScores.size() > 0 )35. {36.return ( m_ArrScores.sum() / m_ArrScores.size() );37. }38.else39. {40.return 0;41. }42. }43.const string& GetName() const44. {45.return sz_Name;46. }47.double& operator[]( int i)48. {49.return m_ArrScores[ i ];50. }51.double operator[]( int i ) const52. {53.return m_ArrScores[ i ];54. }55. ostream& CStudent::arr_out( ostream& os ) const56. {57.int i;58.int lim = m_ArrScores.size();59.if ( lim > 0 )60. {61.for ( i = 0; i < lim; i++ )62. {63. os << m_ArrScores[ i ] << " ";64.if ( 4 == i % 5 )65. {66. os << endl;67. }68. }69.if ( 0 != i % 5 )70. {71. os << endl;72. }73. }74.else75. {76. os << "empty array";77. }78.return os;79. }80.friend istream& operator >>( istream& is, CStudent& stu );81.friend istream& operator <<( istream& os, const CStudent& stu );82.friend istream& getline( istream& is, const CStudent& stu );83. ~CStudent(){};84.private:85. string sz_Name;86. ArrayDb m_ArrScores;87.};88.89.istream& operator >>( istream& is, CStudent& stu )90.{91. is >> stu.sz_Name;92.return is;93.}94.95.ostream& operator <<( ostream& os, const CStudent&stu )96.{97. os << "this student name is：" << stu.GetName() << endl;98. os << "this student scores is：" << endl;99. stu.arr_out( os );100.return os;101.}102.istream& getline( istream& is, const CStudent& stu )103.{104. getline( is, stu.sz_Name );105.return is;106.}107.108.const int puplis = 3;109.const int quizzes = 5;110.void set( CStudent& sa, int n );111.112.int _tmain(int argc, _TCHAR* argv[])113.{114. CStudent ada[ puplis ] = { CStudent( quizze s ), CStudent( quizzes ), CStudent( quizzes ) }; 115.int i;116.for ( i = 0; i < puplis; ++i )117. {118. set( ada[ i ], quizzes );119. }120. cout << "\nStudent List：" << endl;121.for ( i = 0; i < puplis; ++i )122. {123. cout << ada[ i ].GetName() << endl; 124. }125. cout << "\nResults：" << endl;126.for ( i = 0; i < puplis; i++ )127. {128. cout << endl << ada[ i ];129. cout << "average" << ada[ i ].Average() << endl;130. }131. cout << "Done." << endl;132.133.return 0;134.}135.136.void set( CStudent& sa, int n )137.{138. cout << "Please enter the student name：" << endl;139. getline( cin, sa );140. cout << "Please enter " << n << "quiz score s：" << endl;141.for ( int i = 0; i < n; i++ )142. {143. cin >> sa[ i ];144. }145.while( '\n' != cin.get() )146. {147.continue;148. }149.}// 在istream& getline( istream& is, const CStudent& stu ){getline( is, stu.sz_Name );return is;}//const CStudent& stu导致递归修改之后的版本[cpp]view plaincopyprint?1.// readBook2.cpp : 定义控制台应用程序的入口点。

2.//3.4.#include "stdafx.h"5.#include "iostream"ing namespace std;7.#include "valarray"8.#include "string"9.10.class CStudent11.{12.public:13.typedef std::valarray<double> ArrayDb;14. CStudent() : sz_Name( "Null Student" ), m_ArrScores()15. {16. }17. CStudent( const string& name ) : sz_Name( name), m_ArrScores()18. {19. }20.explicit CStudent( int n ) : sz_Name( "Nully"), m_ArrScores( n )21. {22. }23. CStudent( const string& name, int n ) : sz_Name( name ), m_ArrScores( n )24. {25. }26. CStudent( const string& name, const ArrayDb& a) : sz_Name( name ), m_ArrScores( a )27. {28. }29. CStudent( const char* name, const double* pd,int n ) : sz_Name( name ), m_ArrScores( pd, n )30. {31. }32.double Average() const34.if ( m_ArrScores.size() > 0 )35. {36.return ( m_ArrScores.sum() / m_ArrScores.size() );37. }38.else39. {40.return 0;41. }42. }43.const string& GetName() const44. {45.return sz_Name;46. }47.double& operator[]( int i)48. {49.return m_ArrScores[ i ];50. }51.double operator[]( int i ) const52. {53.return m_ArrScores[ i ];55. ostream& CStudent::arr_out( ostream& os ) const56. {57.int i;58.int lim = m_ArrScores.size();59.if ( lim > 0 )60. {61.for ( i = 0; i < lim; i++ )62. {63. os << m_ArrScores[ i ] << " ";64.if ( 4 == i % 5 )65. {66. os << endl;67. }68. }69.if ( 0 != i % 5 )70. {71. os << endl;72. }73. }74.else75. {76. os << "empty array";77. }78.return os;79. }80.friend istream& operator >>( istream& is, CStudent& stu );81.friend istream& operator <<( istream& os, const CStudent& stu );82.friend istream& getline( istream& is, CStudent& stu );83. ~CStudent(){};84.private:85. string sz_Name;86. ArrayDb m_ArrScores;87.};88.89.istream& operator >>( istream& is, CStudent& stu )90.{91. is >> stu.sz_Name;92.return is;93.}94.95.ostream& operator <<( ostream& os, const CStudent&stu )96.{97. os << "this student name is：" << stu.GetName() << endl;98. os << "this student scores is：" << endl;99. stu.arr_out( os );100.return os;101.}102.istream& getline( istream& is, CStudent& stu )103.{104. getline( is, stu.sz_Name );105.return is;106.}107.108.const int puplis = 3;109.const int quizzes = 5;110.void set( CStudent& sa, int n );111.112.int _tmain(int argc, _TCHAR* argv[])113.{114. CStudent ada[ puplis ] = { CStudent( quizze s ), CStudent( quizzes ), CStudent( quizzes ) }; 115.int i;116.for ( i = 0; i < puplis; ++i )117. {118. set( ada[ i ], quizzes );119. }120. cout << "\nStudent List：" << endl;121.for ( i = 0; i < puplis; ++i )122. {123. cout << ada[ i ].GetName() << endl; 124. }125. cout << "\nResults：" << endl;126.for ( i = 0; i < puplis; i++ )127. {128. cout << endl << ada[ i ];129. cout << "average" << ada[ i ].Average() << endl;130. }131. cout << "Done." << endl;132.133.return 0;134.}135.136.void set( CStudent& sa, int n )137.{138. cout << "Please enter the student name：";139. getline( cin, sa );140. cout << "Please enter " << n << "quiz score s：" << endl;141.for ( int i = 0; i < n; i++ )142. {143. cin >> sa[ i ];144. }145.while( '\n' != cin.get() )146. {147.continue;148. }149.}私有继承c++还有另一种实现has-a关系的途径----私有继承。