编写一个C++程序要求实现：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，以下是代码实现：

#include<iostream>
using namespace std;

class Complex{
private:
    double real; // 复数的实部
    double imag; // 复数的虚部
public:
    Complex(double r = 0, double i = 0) :real(r), imag(i) {} // 构造函数

    Complex operator + (const Complex& c2) const{ // 加法重载
        return Complex(real + c2.real, imag + c2.imag);
    }

    Complex operator - (const Complex& c2) const{ // 减法重载
        return Complex(real - c2.real, imag - c2.imag);
    }

    Complex operator * (const Complex& c2) const{ // 乘法重载
        return Complex(real * c2.real - imag * c2.imag, real * c2.imag + imag * c2.real);
    }

    Complex operator / (const Complex& c2) const{ // 除法重载
        double denominator = c2.real * c2.real + c2.imag * c2.imag;
        return Complex((real * c2.real + imag * c2.imag) / denominator, (imag * c2.real - real * c2.imag) / denominator);
    }

    Complex operator ++ () { // 前置自增运算符重载
        ++real;
        return *this;
    }

    Complex operator -- () { // 前置自减运算符重载
        --real;
        return *this;
    }

    Complex operator ++ (int) { // 后置自增运算符重载
        Complex temp = *this;
        real++;
        return temp;
    }

    Complex operator -- (int) { // 后置自减运算符重载
        Complex temp = *this;
        real--;
        return temp;
    }

    friend ostream& operator << (ostream& out, const Complex& c){ // 输出运算符重载
        out << c.real << "+" << c.imag << "i";
        return out;
    }

    friend istream& operator >> (istream& in, Complex& c){ // 输入运算符重载
        cout << "请输入实部和虚部：";
        in >> c.real >> c.imag;
        return in;
    }

    operator double() const{ // double转Complex运算符重载
        return real;
    }
};

int main(){
    Complex c1(1, 2), c2(3, 4);
    cout << "c1 = " << c1 << endl;
    cout << "c2 = " << c2 << endl;

    Complex c3 = c1 + c2;
    cout << "c1 + c2 = " << c3 << endl;

    Complex c4 = c1 - c2;
    cout << "c1 - c2 = " << c4 << endl;

    Complex c5 = c1 * c2;
    cout << "c1 * c2 = " << c5 << endl;

    Complex c6 = c1 / c2;
    cout << "c1 / c2 = " << c6 << endl;

    ++c1;
    cout << "++c1 = " << c1 << endl;

    --c1;
    cout << "--c1 = " << c1 << endl;

    c1++;
    cout << "c1++ = " << c1 << endl;

    c1--;
    cout << "c1-- = " << c1 << endl;

    double d = 5.6;
    Complex c7 = d;
    cout << "c7 = " << c7 << endl;

    Complex c8;
    cin >> c8;
    cout << "c8 = " << c8 << endl;

    return 0;
}

这个程序定义了一个 `Complex` 类，其中包含了 `real` 和 `imag` 两个私有成员变量，代表复数的实部和虚部。

程序中重载了加减乘除、前置后置自增自减、输出和输入运算符，实现了复数的基本运算和输出输入功能。

此外还重载了一个运算符，将 `double` 类型的数转换成 `Complex` 类型。

在 `main` 函数中，我们创建了两个 `Complex` 类型的对象 `c1` 和 `c2`，并对它们进行了加减乘除、自增自减、输出输入等操作。