重载运算符

project 1 重载()运算符

#include <iostream>
using namespace std;

class Clock {
private:
    int hour, minute, second;
public:
    Clock(int h, int m, int s) : hour(h), minute(m), second(s) {}
    // 重载()运算符
    void operator()(int h, int m, int s) {
        hour = h;
        minute = m;
        second = s;
    }
    void ShowTime() {
        cout << hour << ":" << minute << ":" << second << endl;
    }
};

int main(int argc, char const *argv[])
{
    Clock t1(12, 34, 45);
    t1.ShowTime();
    t1.operator()(10, 21, 32);
    t1.ShowTime();
    return 0;
}

project 2 重载()和[]运算符

#include<iostream>
using namespace std;
class X
{
public:
    int operator() (int i = 0) {
        cout << "X operator (" << i << ")" << endl;
        return i;
    }
    int operator[] (int j) {
        cout << "X operator [" << j << "]" << endl;
        return j;
    }
};
int main (void)
{   
    X obj;
    int i = obj(1);
    cout << i << endl;
    int j = obj[234];
    cout << j << endl;
    return 0;
}
X operator (1)
1
X operator [234]
234

sublime的代码复制到VScode之后会出现空格不一致的问题，解决方法是在sublime中把tab替换为空格
Perference->setting添加

"tab_size": 4,
"translate_tabs_to_spaces": true

project 3 员工工资系统

struct person {
    double salary;
    char* name;
};

class SalaryManage {
private:
    person* employee;
    int max;    // 可容纳员工数
    int count;  // 当前员工数
public:
    SalaryManage(int Max = 0) {
        max = Max;
        count = 0;
        employee = new person[max];
    }
    double &operator [] (const char* Name) {
        person* ptr;
        for (ptr = employee; ptr <= employee + count; ptr++) {
            if (strcmp(ptr->name, Name) == 0) {
                return ptr->salary;
            }
            ptr = employee + count; // 跳到最后一个
            count++;                // 员工数++
            ptr->name = new char[strlen(Name) + 1]; // 新建一个员工
            strcpy(ptr->name, Name);
            ptr->salary = 0;
            return ptr->salary;
        }
    }
    void display() {
        for (int i = 0; i < count; i++) {
            cout << employee[i].name << ": " << employee[i].salary << endl;
        }
    }
};

int main(int argc, char const *argv[])
{
    SalaryManage s(2);
    const char* ch1 = "kavin";
    s[ch1] = 3.2;
    const char* ch2 = "jack";
    s[ch2] = 123.2;
    cout << s[ch1] << endl;
    s.display();

    return 0;
}
3.2
kavin: 3.2
jack: 123.2

C++11不能直接从string字符串转为char*，所以用一个指向字符串常量的指针指向他

project 4 重载二元运算符

#include <iostream>
using namespace std;

class Complex
{
public:
    Complex(int _r = 0, int _i = 0) : r(_r), i(_i) {}
    Complex operator + (Complex input);
    Complex operator - (Complex input);
    void info();
private:
    int r, i;
};

Complex Complex::operator + (Complex input) {
    return Complex(this->r + input.r, this->i + input.i);
}

Complex Complex::operator - (Complex input) {
    return Complex(this->r - input.r, this->i - input.i);
}

void Complex::info() {
    cout << this->r;
    if (this->i > 0) cout << "+";
    if (this->i != 0) cout << this->i << "i" << endl;
}

int main(int argc, char const *argv[])
{
    Complex a(2, -3);
    a.info();
    Complex b(3, 4);
    b.info();
    Complex c = a + b;
    c.info();
    Complex d = a - b;
    d.info();
    return 0;
}
2-3i
3+4i
5+1i
-1-7i

project5 自定义String类

#include <iostream>
#include <cstring>
using namespace std;

class String
{
public:
    String(const char* = "");
    ~String(){}
    friend ostream& operator << (ostream& os, const String& s) {
        return os << s.sPtr;
    }
    // 声明为友元函数，参数要与实际需要的参数相同
    friend String operator + (const String& a, const String& b);
    const String& operator = (const String&);
    const String& operator += (const String&);
    bool operator == (const String&);
    bool operator != (const String&);
    bool operator < (const String&);
    char& operator [] (int index);
    int getLength() { return this->length; }

private:
    char* sPtr;
    int length;
};

String::String(const char* str) {
    this->sPtr = new char[strlen(str) + 1];
    strcpy(this->sPtr, str);
    this->length = strlen(str);
}

// 友元就不需要作用域String::了
String operator + (const String& a, const String& b) {
    String res;
    res.sPtr = new char[a.length + b.length + 1];
    strcpy(res.sPtr, a.sPtr);
    strcat(res.sPtr, b.sPtr);
    return String(res.sPtr);
}
const String& String::operator = (const String& s) {
    cout << "copy assignment" << endl;
    this->length = s.length;
    strcpy(this->sPtr, s.sPtr);
    return *this;
}

const String& String::operator += (const String& s) {
    char* temp = this->sPtr;
    this->length += s.length;
    this->sPtr = new char[this->length + 1];
    strcpy(this->sPtr, temp);
    strcat(this->sPtr, s.sPtr);
    delete[] temp;
    return *this;
}

bool String::operator == (const String& s) {
    return strcmp(this->sPtr, s.sPtr) == 0;
}

bool String::operator != (const String& s) {
    return !(*this == s);
}

bool String::operator < (const String& s) {
    return strcmp(this->sPtr, s.sPtr) < 0;
}

char& String::operator [] (int index) {
    return this->sPtr[index];
}

int main(int argc, char const *argv[])
{
    String s1("hello");
    cout << "s1=" << s1 << endl;
    
    String s2;
    s2.operator=(s1);
    cout << "s2=" << s2 << endl;

    s2 += " world";
    cout << "s2=" << s2 << endl;

    for (int i = 0; i < s2.getLength(); i++) {
        cout << s2[i] << " ";
    }
    cout << endl;

    String s3 = s1 + s2;
    cout << "s3=" << s3 << endl;

    String s4("hello world");
    if (s2 != s4) {
        cout << "s2!=s4" << endl;
    } else {
        cout << "s2==s4" << endl;
    }
    String str1("abd");
    String str2("abc");
    if (str1 < str2) {
        cout << "str1 < str2" << endl;
    } else {
        cout << "str1 >= str2" << endl;
    }
    return 0;
}
s1=hello
copy assignment
s2=hello
s2=hello world
h e l l o   w o r l d 
s3=hellohello world
s2==s4
str1 >= str2