Question

所以我正在学习C ++，我必须创建一个重载函数，并从中获取一组数字中最大的数字。这适用于2个数字但是当我注释掉2个数字的函数调用并尝试3个数字时，它给了我很多错误。我需要一双新眼睛来看我的代码，看看我做错了什么。

#include <iostream>
using namespace std;

// function prototypes
double max(double numberOne, double numberTwo);
double max(double numberOne, double numberTwo, double numberThree);

int main()
{
    int numberOne,
        numberTwo,
        numberThree;

    // user input
    cout << "Input number 1: " << endl;
    cin >> numberOne;
    cout << "Input number 2: " << endl;
    cin >> numberTwo;
    cout << "Input number 3: " << endl;
    cin >> numberThree;

    cout << "The largest of " << numberOne << " and " << numberTwo << ": " << max(numberOne, numberTwo) << endl;
    cout << "The largest of " << numberOne << ", " << numberTwo << ", and " << numberThree << ": " << max(numberOne, numberTwo, numberThree) << endl;

    return 0;
}

// function declarations
double max(double numberOne, double numberTwo) {
    // if number one is greater than number two return that
    // otherwise return numberTwo as the greater value
    if (numberOne > numberTwo) {
        return numberOne;
    } else {
        return numberTwo;
    }
}

double max(double numberOne, double numberTwo, double numberThree) {
    // compare 1 and 2 to see which is greater
    if (numberOne > numberTwo) {
        if (numberOne > numberThree) {
            // 2 is greater return it
            return numberOne;
        } else {
            // else 3 is greater return that
            return numberThree;
        }
    } else {
        if (numberTwo > numberThree) {
            // 2 is greater return it
            return numberTwo;
        } else {
            // else 3 is greater return that
            return numberThree;
        }
    }
}

Answer 1

using namespace std;

// function prototypes
double max( ... )

通过在此上下文中定义具有该名称的函数，您遇到与std :: max的冲突。

将max放入自己的命名空间，不要导入std，或两者兼而有之。作为折衷方案，您可以using std using std::vector; using std::map; using std::string;来代替所有这些名称。像这样：

{{1}}

As an aside -- I'm floored -- it's as if I summoned this question myself very recently！

Answer 2

使用::max()代替max()访问您的版本，因此不会与std::max()冲突。像这样：

cout << "The largest of " << numberOne << " and " << numberTwo << ": " << ::max(numberOne, numberTwo) << endl;
cout << "The largest of " << numberOne << ", " << numberTwo << ", and " << numberThree << ": " << ::max(numberOne, numberTwo, numberThree) << endl;

但是，更优雅的解决方案是实际利用std::max()和/或为您的功能使用不同的名称。

Answer 3

问题是max不明确。

您可以重命名您的功能（类似于my_max），

或使用范围解析运算符来调用您的（全局）版本，例如。 :: MAX（）

带参数评估错误的重载函数

3 个答案: