這里介紹了:
1.++obj和obj++ 如何重載.(添天占位參數)
2.基本的操作符重載過程. 返回類型 operator 操作符 參數
3.友元函數 沒有自帶的 this 指針,在重載操作符的時候,所有的參數都必須在參數中顯示聲明.
4.重載 [] 提取操作符 << >> 流操作符.

#include <iostream>
using namespace std;
// 運算符重載 本質是一個函數



class Complex{
public:
    int a;
    int b;
    
  //  friend Complex operator+(Complex &c1,Complex &c2);
    
    
    Complex(int a = 0,int b =0){
        this->a = a;
        this->b = b;
    }
    
//    Complex operator+(Complex &c1){
//        
//        Complex temp = Complex(this->a+c1.a,this->b+c1.b);
//        
//        return temp;
//    }
    
    // 前置
    Complex operator--(){
        this->a--;
        this->b--;
        
        return *this;
    }
    
    //占位參數來 區別 是 obj-- 還是 --obj   這里使用一個偽參數 表示后置的 obj--;
    Complex operator--(int){
        this->a--;
        this->b--;
        
        return *this;
    }
    Complex operator+(int z){
        
        this->a = this->a + z;
        return *this;
    }
    
    
public:
    void printCom(){
        cout<<a<<"+"<<b<<endl;
    }
    
    
};

Complex operator+(Complex &c1,Complex &c2){
    
    Complex tmp(c1.a+c2.a,c1.b+c2.b);
    
    
    
    return tmp;
}

class vector{
    
public:
    vector(int size = 1);
    
    int & operator[](int i);
    friend ostream& operator<<(ostream& output,vector&);
    friend istream& operator>>(istream& input, vector&);
    
    ~vector();
private:
    int *v;
    int len;
};

vector::vector(int size){
    
    if (size<= 0 || size>100) {
        cout<<"The size of "<<size<<"is null!\n";abort();
    }
    v = new int[size];
    len = size;
}

vector::~vector(){
    delete [] v;
    len = 0;
    
}

//重載提取操作符 判斷數組越界
int &vector::operator[](int i){
    if (i>=0&&i<len) {
        return v[i];
    }
    cout<<"The subscript"<<"is outside!\n"; abort();
    
}

ostream & operator <<(ostream& output,vector& ary){
    
    for (int i = 0; i<ary.len; i++) {
        output<<ary[i]<<"  ";
    }
    output<<endl;
    
    return output;
}

istream & operator >> (istream & input,vector &ary){
    
    for (int i = 0; i<ary.len; i++) {
        input>>ary[i];
    }
    return input;
}


int main(int argc, const char * argv[]) {
    // insert code here...
    std::cout << "Hello, World!\n";
    
    
    Complex c1(1,2),c2(3,4);
    
    Complex c3 = c1+c2;
    c3.printCom();
    
    c3--;
    --c3;
    
    
    /**
     *  在第一個參數需要隱式轉換的情形下,使用友元函數重載運算符是正確的選擇
     友元函數沒有this 指針,所需操作數 都必須在參數表顯式生命,很容易實現類型的隱式轉換.
     */
    c3 = c3+4;
    c3.printCom();
    
    int k;
    cout<<"Input the length of vetor A:\n";
    cin>>k;
    
    vector A(k);
    
    cout<<"Input the elements of vetor A:\n";
    cin>>A;
    cout<<"Output the elements of vector A:\n";
    cout<<A;
    
    
    return 0;
}