崔毅东 C++程序设计入门(下) 第8单元:年年岁岁花相似– 运算符重载 笔记

#include <string>
#include <iostream>
#include <sstream>
#include <vector>

// For more details about "string", "vector",
//    and "stringstream", please refer to book
//    <<The C++ Standard Library - 
//      A Tutorial and Reference>>

using namespace std;
int main() {
    
    // Student1~4
    string sname("Student"), snumber("1");
    for (int i = 1; i <= 4; i++) {
        cout << sname + snumber << endl; 
        snumber[0]++;
    }

    // Student5~7
    // copy the contents from sname;
    vector<char> vname(sname.begin(), sname.end());
    vname.resize(vname.size() + 1);
    for (int i = 5; i <= 7; i++) {
        vname[vname.size() - 1] = static_cast<char>(i + '0');
        for (unsigned int j = 0; j < vname.size(); j++)
            cout << vname[j];
        cout << endl;
    }
    
    // Student8~10
    stringstream sequenceNo("", ios::out|ios::app);
    for (int i = 8; i <= 10; i++) {
        sequenceNo.str("Student");    // Set the contents
        sequenceNo << i;       // convert integer to string
        cout << sequenceNo.str() << endl; 
    }
    
    // compare two string and show the result in bool type
    cout << boolalpha << "Student1 > Student2 : " <<
            (string("Student1") > string("Student2"));
            
    return 0;            
}

第02节：有理数类

Rational.h

#ifndef RATIONL_H
#define RATIONL_H
#include <string>

using namespace std;

class Rational {
public:
  Rational();
  Rational(long numerator, long denominator);
  long getNumerator();
  long getDenominator();
  Rational add(Rational &secondRational);
  Rational subtract(Rational &secondRational);
  Rational multiply(Rational &secondRational);
  Rational divide(Rational &secondRational);
  int compareTo(Rational &secondRational);
  bool equals(Rational &secondRational);
  int intValue();
  double doubleValue();
  string toString();

private:
  long numerator_;
  long denominator_;
  static long gcd(long n, long d);
};

#endif

Rational.cpp

#include <iostream>
#include <sstream>

#include <cmath>

#include "Rational.h"

using namespace std;

Rational::Rational()
{
  numerator_ = 0;
  denominator_ = 1;
}

Rational::Rational(long numerator, long denominator)
{
  long factor = gcd(numerator, denominator);
  numerator_ = ((denominator > 0) ? 1 : -1) * numerator / factor;
  denominator_ = abs(denominator) / factor;
}

long Rational::getNumerator()
{
  return numerator_;
}

long Rational::getDenominator()
{
  return denominator_;
}

/** Find GCD of two numbers */
long Rational::gcd(long n, long d) {
  long n1 = abs(n);
  long n2 = abs(d);
  int gcd = 1;

  for (int k = 1; k <= n1 && k <= n2; k++)
  {
    if (n1 % k == 0 && n2 % k == 0)
      gcd = k;
  }

  return gcd;
}

Rational Rational::add(Rational &secondRational)
{
  long n = numerator_ * secondRational.getDenominator() +
    denominator_ * secondRational.getNumerator();
  long d = denominator_ * secondRational.getDenominator();
  return Rational(n, d);
}

Rational Rational::subtract(Rational &secondRational)
{
  long n = numerator_ * secondRational.getDenominator()
    - denominator_ * secondRational.getNumerator();
  long d = denominator_ * secondRational.getDenominator();
  return Rational(n, d);
}

Rational Rational::multiply(Rational &secondRational)
{
  long n = numerator_ * secondRational.getNumerator();
  long d = denominator_ * secondRational.getDenominator();
  return Rational(n, d);
}

Rational Rational::divide(Rational &secondRational)
{ // We don't handle the case of secondRational being 0
  long n = numerator_ * secondRational.getDenominator();
  // private data in another object of the same type
  //    can be directly visited. 
  long d = denominator_ * secondRational.numerator_; 
  return Rational(n, d);
}

int Rational::compareTo(Rational &secondRational)
{
  Rational temp = this->subtract(secondRational);
  if (temp.getNumerator() < 0)
    return -1;
  else if (temp.getNumerator() == 0)
    return 0;
  else
    return 1;
}

bool Rational::equals(Rational &secondRational)
{
  if (this->compareTo(secondRational) == 0)
    return true;
  else
    return false;
}

int Rational::intValue()
{
  return getNumerator() / getDenominator();
}

double Rational::doubleValue()
{
  return 1.0 * getNumerator() / getDenominator();
}

//string Rational::toString()
//{
//  char s1[20], s2[20];
//  itoa(numerator_, s1, 10); // Convert int to string s1
//  itoa(denominator_, s2, 10); // Convert int to string s2
//
//  if (denominator_ == 1)
//    return string(s1);
//  else
//    return string(strcat(strcat(s1, "/"), s2));
//}

string Rational::toString()
{
  stringstream stringStream;
  if (denominator_ != 1) {
    stringStream << numerator_ << "/" << denominator_;
  } else {
    stringStream << numerator_;  
  }
  
  return string(stringStream.str());
}

TestRationalClass.cpp

#include <iostream>
#include "Rational.h"
using namespace std;

int main()
{
  // Create and initialize two rational numbers r1 and r2.
  Rational r1(4, 2);
  Rational r2(2, 3);

  // Test toString, add, substract, multiply, and divide
  cout << r1.toString() << " + " << r2.toString() << " = " << 
          r1.add(r2).toString() << endl;
  cout << r1.toString() << " - " << r2.toString() << " = " << 
          r1.subtract(r2).toString() << endl;
  cout << r1.toString() << " * " << r2.toString() << " = " << 
          r1.multiply(r2).toString() << endl;
  cout << r1.toString() << " / " << r2.toString() << " = " << 
          r1.divide(r2).toString() << endl;

  // Test intValue and double
  cout << "r2.intValue()" << " is " << r2.intValue() << endl;
  cout << "r2.doubleValue()" << " is " << r2.doubleValue() << endl;

  // Test compareTo and equal
  cout << "r1.compareTo(r2) is " << r1.compareTo(r2) << endl;
  cout << "r2.compareTo(r1) is " << r2.compareTo(r1) << endl;
  cout << "r1.compareTo(r1) is " << r1.compareTo(r1) << endl;
  cout << "r1.equals(r1) is " << r1.equals(r1) << endl;
  cout << "r1.equals(r2) is " << r1.equals(r2) << endl;

  return 0;
}

第03节：运算符函数以及简写运算符重载

第04节：重载[]运算符

第05节：重载一元运算符

第06节：重载流提取/插入运算符以及对象转换运算符

u08s06 - 如果将流操作运算符重载为类的成员函数…
如果将流操作运算符重载为类的成员函数，会发生哪些反常的事情？

打开你的脑洞，用代码说明
答：会使得你将不得不使用如下反人类的方式调用

扫描二维码关注公众号，回复： 5316737 查看本文章

MyCircle c1;

c1 >> std::cin;

c1 << std::cout;

（by wohaaitinciu）

第07节：新有理数类的示例

NewRational.h

#ifndef NEWRATIONL_H
#define NEWRATIONL_H

#include <string>
using namespace std; 

class Rational
{
public:
  Rational();
  Rational(long numerator, long denominator);
  long getNumerator();
  long getDenominator();
  Rational add(Rational &secondRational);
  Rational subtract(Rational &secondRational);
  Rational multiply(Rational &secondRational);
  Rational divide(Rational &secondRational);
  int compareTo(Rational &secondRational);
  bool equals(Rational &secondRational);
  int intValue();
  double doubleValue();
  string toString();

  // Define function operators for relational operators
  bool operator<(Rational &secondRational);
  bool operator<=(Rational &secondRational);
  bool operator>(Rational &secondRational);
  bool operator>=(Rational &secondRational);
  bool operator!=(Rational &secondRational);
  bool operator==(Rational &secondRational);

  // Define function operators for arithmetic operators
  Rational operator+(Rational &secondRational);
  Rational operator-(Rational &secondRational);
  Rational operator*(Rational &secondRational);
  Rational operator/(Rational &secondRational);

  // Define function operators for shorthand operators
  Rational operator+=(Rational &secondRational);
  Rational operator-=(Rational &secondRational);
  Rational operator*=(Rational &secondRational);
  Rational operator/=(Rational &secondRational);

  // Define function operator []
  long& operator[](const int &index);

  // Define function operators for prefix ++ and --
  Rational operator++();
  Rational operator--();

  // Define function operators for postfix ++ and --
  Rational operator++(int dummy);
  Rational operator--(int dummy);

  // Define function operators for unary + and -
  Rational operator+();
  Rational operator-();

  // Define the output and input operator
  friend ostream &operator<<(ostream &stream, Rational &rational);
  friend istream &operator>>(istream &stream, Rational &rational);

  // Define function operator for conversion
  operator double();

private:
  long numerator_;
  long denominator_;
  static long gcd(long n, long d);
};

#endif

NewRational.cpp

#include <iostream>
#include <sstream>

#include <cmath>
#include <cstdlib>

#include "NewRational.h"

using namespace std;

Rational::Rational()
{
  numerator_ = 0;
  denominator_ = 1;
}

Rational::Rational(long numerator, long denominator)
{
  long factor = gcd(numerator, denominator);
  numerator_ = ((denominator > 0) ? 1 : -1) * numerator / factor;
  denominator_ = abs(denominator) / factor;
}

long Rational::getNumerator()
{
  return numerator_;
}

long Rational::getDenominator()
{
  return denominator_;
}

/** Find GCD of two numbers */
long Rational::gcd(long n, long d) {
  long n1 = abs(n);
  long n2 = abs(d);
  int gcd = 1;

  for (int i = 1; i <= n1 && i <= n2; i++)
  {
    if (n1 % i == 0 && n2 % i == 0)
      gcd = i;
  }

  return gcd;
}

Rational Rational::add(Rational &secondRational)
{
  long n = numerator_ * secondRational.getDenominator() +
    denominator_ * secondRational.getNumerator();
  long d = denominator_ * secondRational.getDenominator();
  return Rational(n, d);
}

Rational Rational::subtract(Rational &secondRational)
{
  long n = numerator_ * secondRational.getDenominator() -
           denominator_ * secondRational.getNumerator();
  long d = denominator_ * secondRational.getDenominator();
  return Rational(n, d);
}

Rational Rational::multiply(Rational &secondRational)
{
  long n = numerator_ * secondRational.getNumerator();
  long d = denominator_ * secondRational.getDenominator();
  return Rational(n, d);
}

Rational Rational::divide(Rational &secondRational)
{
  long n = numerator_ * secondRational.getDenominator();
  long d = denominator_ * secondRational.numerator_;
  return Rational(n, d);
}

int Rational::compareTo(Rational &secondRational)
{
  Rational temp = this->subtract(secondRational);
  if (temp.getNumerator() < 0)
    return -1;
  else if (temp.getNumerator() == 0)
    return 0;
  else
    return 1;
}

bool Rational::equals(Rational &secondRational)
{
  if (this->compareTo(secondRational) == 0)
    return true;
  else
    return false;
}

int Rational::intValue()
{
  return getNumerator() / getDenominator();
}

double Rational::doubleValue()
{
  return 1.0 * getNumerator() / getDenominator();
}

string Rational::toString() 
{
  stringstream stringStream;
  if (denominator_ != 1) {
    stringStream << numerator_ << "/" << denominator_;
  } else {
    stringStream << numerator_;  
  }
  
  return string(stringStream.str());
}

// Define function operators for relational operators
bool Rational::operator<(Rational &secondRational)
{
  return (this->compareTo(secondRational) < 0);
}

bool Rational::operator<=(Rational &secondRational)
{
  return (this->compareTo(secondRational) <= 0);
}

bool Rational::operator>(Rational &secondRational)
{
  return (this->compareTo(secondRational) > 0);
}

bool Rational::operator>=(Rational &secondRational)
{
  return (this->compareTo(secondRational) >= 0);
}

bool Rational::operator!=(Rational &secondRational)
{
  return (this->compareTo(secondRational) != 0);
}

bool Rational::operator==(Rational &secondRational)
{
  return (this->compareTo(secondRational) == 0);
}

// Define function operators for arithmetic operators
Rational Rational::operator+(Rational &secondRational)
{
  return this->add(secondRational);
}

Rational Rational::operator-(Rational &secondRational)
{
  return this->subtract(secondRational);
}

Rational Rational::operator*(Rational &secondRational)
{
  return this->multiply(secondRational);
}

Rational Rational::operator/(Rational &secondRational)
{
  return this->divide(secondRational);
}

// Define function operators for shorthand operators
Rational Rational::operator+=(Rational &secondRational)
{
  *this = this->add(secondRational);
  return (*this);
  //return this->add(secondRational);
}

Rational Rational::operator-=(Rational &secondRational)
{
  *this = this->subtract(secondRational);
  return (*this);
}

Rational Rational::operator*=(Rational &secondRational)
{
  *this = this->multiply(secondRational);
  return (*this);
}

Rational Rational::operator/=(Rational &secondRational)
{
  *this = this->divide(secondRational);
  return *this;
}

// Define function operator []
long& Rational::operator[](const int &index)
{
  if (index == 0)
    return numerator_;
  else if (index == 1)
    return denominator_;
  else
  {
    cout << "subscript error" << endl;
    exit(0);
  }
}

// Define function operators for prefix ++ and --
Rational Rational::operator++()
{
  numerator_ += denominator_;
  return *this;
}

Rational Rational::operator--()
{
  numerator_ -= denominator_;
  return *this;
}

// Define function operators for postfix ++ and --
Rational Rational::operator++(int dummy)
{
  Rational temp(numerator_, denominator_);
  numerator_ += denominator_;
  return temp;
}

Rational Rational::operator--(int dummy)
{
  Rational temp(numerator_, denominator_);
  numerator_ -= denominator_;
  return temp;
}

// Define function operators for unary + and -
Rational Rational::operator+()
{
  return *this;
}

Rational Rational::operator-()
{
  numerator_ *= -1;
  return *this;
}

// Define the output and input operator
ostream &operator<<(ostream &str, Rational &rational)
{
  // cout << rational.numerator_ << " / " << rational.denominator_;
  cout << rational.toString();
  return str;
}

istream &operator>>(istream &str, Rational &rational)
{
  cout << "Enter numerator: ";
  str >> rational.numerator_;

  cout << "Enter denominator: ";
  str >> rational.denominator_;
  return str;
}

// Define function operator for conversion
Rational::operator double()
{
  return doubleValue();
}

TestNewRationalClass.cpp

#include <iostream>
#include <string>

#include "NewRational.h"

using namespace std;

int main()
{
  // Create and initialize two rational numbers r1 and r2.
  Rational r1(4, 2);
  Rational r2(2, 3);

  // Test relational operators
  cout << r1 << " > " << r2 << " is " << (r1 > r2) << endl;
  cout << r1 << " < " << r2 << " is " << (r1 < r2) << endl;
  cout << r1 << " == " << r2 << " is " << (r1 == r2) << endl;
  cout << r1 << " != " << r2 << " is " << (r1 != r2) << endl;

  // Test toString, add, substract, multiply, and divide operators
  cout << r1 << " + " << r2 << " = " << r1 + r2 << endl;
  cout << r1 << " - " << r2 << " = " << r1 - r2 << endl;
  cout << r1 << " * " << r2 << " = " << r1 * r2 << endl;
  cout << r1 << " / " << r2 << " = " << r1 / r2 << endl;

  // Test shorthand operators
  Rational r3(1, 2);
  r3 += r1;
  cout << "r3 is " << r3 << endl;

  // Test function operator []
  Rational r4(1, 2);
  r4[0] = 3; r4[1] = 4;
  cout << "r4 is " << r4 << endl;

  // Test function operators for ++ and --
  r3 = r4++;
  cout << "r3 is " << r3 << endl;
  cout << "r4 is " << r4 << endl;

  // Test function operator for conversion
  cout << "1 + " << r4 << " is " << (1 + r4) << endl;

  return 0;
}

第08节：重载赋值运算符

Date.h

#ifndef DATE_H
#define DATE_H

class Date
{
public:
  Date(int newYear, int newMonth, int newDay);
  int getYear();
  void setYear(int newYear);

private:
  int year;
  int month;
  int day;
};

#endif

Date.cpp

#include "Date.h"

Date::Date(int newYear, int newMonth, int newDay)
{
  year = newYear;
  month = newMonth;
  day = newDay;
}

int Date::getYear()
{
  return year;
}

void Date::setYear(int newYear)
{
  year = newYear;
}

Person2.h

#include "Date.h"

class Person
{
public:
  Person(int id, int year, int month, int day);
  Person(Person &);
  ~Person(); 
  const Person operator=(const Person& person);
  int getId();
  Date * getBirthDate() const; // Return the pointer of the object

private:
  int id;
  Date *birthDate; // The pointer of the object
};

Person2.cpp

#include "Person2.h"

Person::Person(int id, int year, int month, int day)
{
  this -> id = id;
  birthDate = new Date(year, month, day);
}

Person::Person(Person &person)
{
  id = person.id;
  Date *p = person.getBirthDate();
  birthDate = new Date(*p);
}

Person::~Person()
{
    delete birthDate;
}

const Person Person::operator=(const Person& person)
{
  id = person.id;
  Date *p = person.getBirthDate();
  birthDate = new Date(*p);    
  return *this;
}



int Person::getId()
{
  return id;
}

Date * Person::getBirthDate() const
{
  return birthDate; // Return the pointer of the object
}

DefaultAssignmentDemo.cpp

#include <iostream>
#include "Person2.h"
using namespace std;

void displayPerson(Person &person1, Person &person2)
{
  cout << "\tperson1 id: " << person1.getId() << endl;
  cout << "\tperson1 birth year: " <<
    person1.getBirthDate() -> getYear() << endl;
  cout << "\tperson2 id: " << person2.getId() << endl;
  cout << "\tperson2 birth year: " <<
    person2.getBirthDate() -> getYear() << endl;
}

int main()
{
  Person person1(111, 1970, 5, 3);
  Person person2(222, 2000, 11, 8);

  cout << "After creating person1 and person2" << endl;
  displayPerson(person1, person2);

  person1 = person2; // Copy person2 to person1

  cout << "\nAfter copying person2 to person1" << endl;
  displayPerson(person1, person2);

  person2.getBirthDate() -> setYear(1963);

  cout << "\nAfter modifying person2's birthDate" << endl;
  displayPerson(person1, person2);

  cout << "\n" << (person1.getBirthDate() == person2.getBirthDate());
  return 0;
}

u08s08 - 赋值运算符与拷贝构造函数
赋值运算符与拷贝构造函数有很多联系。

比如说，涉及到对象深拷贝构造的时候，我们同时也要为赋值运算符提供重载的深拷贝版本。

那么，下面这几行代码，到底是调用拷贝构造函数还是调用赋值运算符？

尤其是第3行，为什么？

Circle c1;
Circle c2(c1);
Circle c3 = c2;
c1 = c3;
答：Circle c2(c1); // copy ，定义对象c2，调用拷贝构造函数构造对象

Circle c3 = c2; // copy ，定义对象c3，调用拷贝构造函数构造对象

c1 = c3; // assignment（by zj060607）

第09节：运算符重载的更多问题