istream& operator>>(istream& i, User& u)

istream& operator>>(istream& i, User& u) 是一个重载的输入运算符函数，用于从输入流中读取数据并将其存储到User对象中。它的作用是实现自定义的输入操作，使得我们可以使用类似于cin >> u 的语法来输入数据到User对象。

这个函数接受两个参数：一个是输入流对象i，通常是cin；另一个是User对象u的引用，用于存储输入的数据。

在函数体内部，我们可以根据需要从输入流中读取不同类型的数据，并将其赋值给User对象的成员变量。通常情况下，我们会使用输入流对象的提取运算符（>>）来逐个读取数据，并将其赋值给User对象的成员变量。

这个函数的返回类型是istream&，它允许我们进行链式输入操作。也就是说，我们可以连续多次使用这个输入运算符来输入不同的数据。

相关问题

C++Write a program that will prepare a shipping label and determine the cost for a box of any size and mass. five attributes: type double length, width, height, mass, price six attributes: type string senderName, receiverName, senderAddress, receiverAddress, originCountry, destinationCountry (you can shorten names if you like, just make a comment about their meaning) a default constructor – basic initial values for all parameters a user constructor – input sender Name, senderAddress, originCountry a double function volume() – a function to return l×w×h a double function surfArea() – a function to return 2×(l×w+l×h+w×h) a double function girth() – a function to return the perimeter for the two smallest dimensions P=2(x+y), where x and y are the two smalles of l,w,h a double function maxDim() – a function to return the largest dimension from l,w,h a double function pricing() – a function to return the shipping price based on the table above an operator+ function – a function that determines the total cost of shipping (return type double).... (you may decide how to calculate.... a) add prices from both packages, b) apply fee or discount for number of packages) an operator>> function – a function to get the information from the user about the package.... OR.... a set of “ask” functions to ask the same information an operator<< function – a function to type the information in the shipping label format.... OR.... a set of “print” functions – to print the same information

Sure, here's an example program that meets the requirements you've listed:

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

class ShippingBox {
private:
    double length, width, height, mass, price;
    string senderName, receiverName, senderAddress, receiverAddress, originCountry, destinationCountry;

public:
    // default constructor
    ShippingBox() {
        length = width = height = mass = price = 0.0;
        senderName = receiverName = senderAddress = receiverAddress = originCountry = destinationCountry = "";
    }

    // user constructor
    ShippingBox(string sName, string sAddress, string oCountry) {
        senderName = sName;
        senderAddress = sAddress;
        originCountry = oCountry;

        // set other parameters to default values
        receiverName = receiverAddress = destinationCountry = "";
        length = width = height = mass = price = 0.0;
    }

    // volume function
    double volume() {
        return length * width * height;
    }

    // surface area function
    double surfArea() {
        return 2 * (length * width + length * height + width * height);
    }

    // girth function
    double girth() {
        double x = min(min(length, width), height);
        if (x == length) return 2 * (width + height);
        else if (x == width) return 2 * (length + height);
        else return 2 * (length + width);
    }

    // max dimension function
    double maxDim() {
        return max(max(length, width), height);
    }

    // pricing function
    double pricing() {
        // pricing table based on destination country
        if (destinationCountry == "USA") {
            if (mass < 10) return 5.0;
            else if (mass < 20) return 8.0;
            else return 10.0;
        } else if (destinationCountry == "Canada") {
            if (mass < 10) return 7.0;
            else if (mass < 20) return 10.0;
            else return 12.0;
        } else {
            if (mass < 10) return 10.0;
            else if (mass < 20) return 15.0;
            else return 20.0;
        }
    }

    // operator+ function
    double operator+(const ShippingBox& other) {
        return pricing() + other.pricing();
    }

    // operator>> function
    friend istream& operator>>(istream& input, ShippingBox& box) {
        cout << "Enter sender name: ";
        getline(input, box.senderName);
        cout << "Enter sender address: ";
        getline(input, box.senderAddress);
        cout << "Enter origin country: ";
        getline(input, box.originCountry);

        cout << "Enter receiver name: ";
        getline(input, box.receiverName);
        cout << "Enter receiver address: ";
        getline(input, box.receiverAddress);
        cout << "Enter destination country: ";
        getline(input, box.destinationCountry);

        cout << "Enter length: ";
        input >> box.length;
        cout << "Enter width: ";
        input >> box.width;
        cout << "Enter height: ";
        input >> box.height;
        cout << "Enter mass: ";
        input >> box.mass;
        cout << "Enter price: ";
        input >> box.price;

        return input;
    }

    // operator<< function
    friend ostream& operator<<(ostream& output, const ShippingBox& box) {
        output << "Sender: " << box.senderName << ", " << box.senderAddress << ", " << box.originCountry << endl;
        output << "Receiver: " << box.receiverName << ", " << box.receiverAddress << ", " << box.destinationCountry << endl;
        output << "Dimensions (LxWxH): " << box.length << " x " << box.width << " x " << box.height << endl;
        output << "Mass: " << box.mass << " kg" << endl;
        output << "Price: $" << box.price << endl;
        output << "Volume: " << box.volume() << " cubic meters" << endl;
        output << "Surface area: " << box.surfArea() << " square meters" << endl;
        output << "Girth: " << box.girth() << " meters" << endl;
        output << "Max dimension: " << box.maxDim() << " meters" << endl;
        output << "Shipping cost: $" << box.pricing() << endl;

        return output;
    }
};

int main() {
    ShippingBox box1("John Smith", "1234 Main St, Anytown USA", "USA");
    ShippingBox box2;

    cout << "Enter information for box 2:" << endl;
    cin >> box2;

    cout << endl << "Shipping label for box 1:" << endl << box1 << endl;
    cout << "Shipping label for box 2:" << endl << box2 << endl;

    double totalCost = box1 + box2;
    cout << "Total shipping cost: $" << totalCost << endl;

    return 0;
}

This program defines a `ShippingBox` class with the attributes and functions you've specified. It includes a default constructor, a user constructor, and functions to calculate the volume, surface area, girth, max dimension, and pricing of a box. It also includes operator functions to input and output the box information, as well as to calculate the total cost of shipping for two boxes.

Note that the pricing table is based on the destination country and the mass of the box. You can adjust the pricing values as needed or add more pricing tiers for different ranges of mass.

C++Write a C++ program that defines a cmplx struct.The cmplx struct object type should include... Member Variables (public or private, you decide) two variables, each double as listed in the "Background" Public Members a default constructor – define all real and imaginary with zero cmplx() a user constructor – define all real and imaginary with user input, allow I=0 as default value cmplx(double, double=0) a copy constructor – define new unit object based on existing cmplx(const cmplx &) arithmetic operators – define four arithmetic operations for cmplx input + – * / arithmetic overload – define four arithmetic overloads for double input + – * / friend iostream directives – define input and output directives >> << friend arithmetic operator – define four friend operation for double + – * / friend square function – define math for square friend cmplx sq(cmplx &) friend cubic function – define math for cubic 。friend cmplx cu(cmplx &)

Here is a sample implementation of the cmplx struct in C++:

#include<iostream>
#include<cmath>

using namespace std;

struct cmplx {
private:
    double real;
    double imag;
public:
    cmplx(): real(0), imag(0) {}
    cmplx(double r, double i = 0): real(r), imag(i) {}
    cmplx(const cmplx& c): real(c.real), imag(c.imag) {}
    
    friend cmplx operator+(const cmplx& c1, const cmplx& c2) {
        return cmplx(c1.real + c2.real, c1.imag + c2.imag);
    }
    friend cmplx operator-(const cmplx& c1, const cmplx& c2) {
        return cmplx(c1.real - c2.real, c1.imag - c2.imag);
    }
    friend cmplx operator*(const cmplx& c1, const cmplx& c2) {
        return cmplx(c1.real*c2.real - c1.imag*c2.imag, c1.real*c2.imag + c1.imag*c2.real);
    }
    friend cmplx operator/(const cmplx& c1, const cmplx& c2) {
        double d = c2.real*c2.real + c2.imag*c2.imag;
        return cmplx((c1.real*c2.real + c1.imag*c2.imag) / d, (c1.imag*c2.real - c1.real*c2.imag) / d);
    }
    
    friend cmplx operator+(const cmplx& c, double d) {
        return cmplx(c.real + d, c.imag);
    }
    friend cmplx operator-(const cmplx& c, double d) {
        return cmplx(c.real - d, c.imag);
    }
    friend cmplx operator*(const cmplx& c, double d) {
        return cmplx(c.real*d, c.imag*d);
    }
    friend cmplx operator/(const cmplx& c, double d) {
        return cmplx(c.real/d, c.imag/d);
    }
    friend cmplx operator+(double d, const cmplx& c) {
        return c + d;
    }
    friend cmplx operator-(double d, const cmplx& c) {
        return cmplx(d) - c;
    }
    friend cmplx operator*(double d, const cmplx& c) {
        return c*d;
    }
    friend cmplx operator/(double d, const cmplx& c) {
        double d2 = c.real*c.real + c.imag*c.imag;
        return cmplx(d*c.real/d2, -d*c.imag/d2);
    }
    
    friend istream& operator>>(istream& is, cmplx& c) {
        is >> c.real >> c.imag;
        return is;
    }
    friend ostream& operator<<(ostream& os, const cmplx& c) {
        os << c.real << " + " << c.imag << "i";
        return os;
    }
    
    friend cmplx sq(cmplx& c) {
        return c*c;
    }
    friend cmplx cu(cmplx& c) {
        return c*c*c;
    }
};

int main() {
    cmplx a(1, 2), b(3, 4);
    cmplx c = a + b;
    cmplx d = a - b;
    cmplx e = a * b;
    cmplx f = a / b;
    cout << "a = " << a << endl;
    cout << "b = " << b << endl;
    cout << "a + b = " << c << endl;
    cout << "a - b = " << d << endl;
    cout << "a * b = " << e << endl;
    cout << "a / b = " << f << endl;
    cmplx g = a + 2.5;
    cmplx h = 3.7 - b;
    cmplx i = a * 1.5;
    cmplx j = b / 2.0;
    cout << "a + 2.5 = " << g << endl;
    cout << "3.7 - b = " << h << endl;
    cout << "a * 1.5 = " << i << endl;
    cout << "b / 2.0 = " << j << endl;
    cmplx k = 2.5 + a;
    cmplx l = 3.7 - b;
    cmplx m = 1.5 * a;
    cmplx n = 2.0 / b;
    cout << "2.5 + a = " << k << endl;
    cout << "3.7 - b = " << l << endl;
    cout << "1.5 * a = " << m << endl;
    cout << "2.0 / b = " << n << endl;
    cout << "a^2 = " << sq(a) << endl;
    cout << "b^3 = " << cu(b) << endl;
    return 0;
}

In this implementation, the cmplx struct has two private member variables for the real and imaginary parts. It also has a default constructor, a user constructor with a default value for the imaginary part, and a copy constructor. The struct defines arithmetic operators (+, -, *, /) for cmplx input and overloaded arithmetic operators for double input. It also defines input and output directives and friend math functions for square and cube.