号码交换：如何让这个程序的主要功能调用参考功能？

Question

所以我有这个程序，它可以交换用户输入的两个数字，唯一的问题是我无法让主函数调用进行交换的函数，代码如下：

#include <iostream>
using namespace std;

float first, 
second;

void swap(float first, float second);

int main()
{

    // Prompt user to enter the first number. 
    cout << "Enter the first number" << endl;
    cout << "Then hit enter" << endl;
    cin >> first;

    // Prompt user to enter the second number. 
    cout << "Enter the second number" << endl;
    cout << "Then hit enter" << endl;
    cin >> second;

    // Echo print the input.
    cout << endl << "You input the numbers as " << first
         << " and " << second << endl;
    
  swap(first, second);
  
  return 0;
}



void swap(float &number1, float &number2)
{
  number1 = number2;
    number2 = number1;
    // Output the values.
    cout << "After swapping, the values of the two numbers are "
         << number1 << " and " << number2 << endl;
}

Answer 1

在您的函数声明中，您有 first 和 second 按值传递：

void swap(float first, float second);

这需要通过引用传递，如函数定义中所给：

void swap(float &number1, float &number2);

提醒一下，您会注意到当您运行它会打印出 number2 两次。当您交换值时，您需要第三个（临时）变量。

void swap(float &number1, float &number2)
{
    float temp = number1;
    number1 = number2;
    number2 = temp; // We change this to temp because you already changed number1 to
                    // equal number2. If we set number2 = number1, we'd just end up
                    // with the value we started with for number2.
    // Output the values.
    cout << "After swapping, the values of the two numbers are "
         << number1 << " and " << number2 << endl;
}

希望对您有所帮助！祝你好运 class

号码交换：如何让这个程序的主要功能调用参考功能？

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