1. 类的定义，构造函数，成员函数 2．两个复数运算的运算符重载.重载 +、-、*、/、++、--、<<、>>等运算符 3. double型数可以转换成复数

好的，我会记住您的要求，下面是回答您的问题：

1. 类的定义：

class Complex{
private:
    double real;
    double imag;
public:
    Complex(double r = 0.0, double i = 0.0):real(r), imag(i){} //构造函数
    Complex(const Complex& c){real = c.real; imag = c.imag;} //复制构造函数
    Complex& operator=(const Complex& c){real = c.real; imag = c.imag; return *this;} //赋值运算符重载
    Complex operator+(const Complex& c)const{return Complex(real+c.real, imag+c.imag);} //加法运算符重载
    Complex operator-(const Complex& c)const{return Complex(real-c.real, imag-c.imag);} //减法运算符重载
    Complex operator*(const Complex& c)const{return Complex(real*c.real-imag*c.imag, real*c.imag+imag*c.real);} //乘法运算符重载
    Complex operator/(const Complex& c)const{
        double denominator = c.real*c.real + c.imag*c.imag;
        return Complex((real*c.real+imag*c.imag)/denominator, (imag*c.real-real*c.imag)/denominator); //除法运算符重载
    }
    Complex& operator++(){ //前置++运算符重载
        ++real;
        return *this;
    }
    Complex operator++(int){ //后置++运算符重载
        Complex c(*this);
        real++;
        return c;
    }
    Complex& operator--(){ //前置--运算符重载
        --real;
        return *this;
    }
    Complex operator--(int){ //后置--运算符重载
        Complex c(*this);
        real--;
        return c;
    }
    friend istream& operator>>(istream& in, Complex& c){ //输入运算符重载
        in >> c.real >> c.imag;
        return in;
    }
    friend ostream& operator<<(ostream& out, const Complex& c){ //输出运算符重载
        out << c.real << "+" << c.imag << "i";
        return out;
    }
    operator double(){return real;} //double型转换成复数运算符重载
};

2. 复数运算符重载：

Complex operator+(const Complex& c1, const Complex& c2){return c1 + c2;}
Complex operator-(const Complex& c1, const Complex& c2){return c1 - c2;}
Complex operator*(const Complex& c1, const Complex& c2){return c1 * c2;}
Complex operator/(const Complex& c1, const Complex& c2){return c1 / c2;}
Complex& operator++(Complex& c){return ++c;}
Complex operator++(Complex& c, int){return c++;}
Complex& operator--(Complex& c){return --c;}
Complex operator--(Complex& c, int){return c--;}
ostream& operator<<(ostream& out, const Complex& c){out << c; return out;}
istream& operator>>(istream& in, Complex& c){in >> c; return in;}

3. double型转换成复数：

Complex(double r = 0.0, double i = 0.0):real(r), imag(i){}
Complex(double r):real(r), imag(0){}

以上是对您的问题的回答，希望能够帮到您！