7.2-function-overloading

Bilibili 7.2

1背景-不同类型的四舍五入-C和C++的实现

2 函数重载实现function overloading fulfillment

• The compiler will preform name lookup
• Argument-dependent lookup, also known as ADL.
• The return type will not be considered in name lookup.

That is to say, 相同的函数必须是函数名和参数列表都相同的函数。

3 实例讲解

#include <iostream>

using namespace std;

int sum(int x, int y)
{
    cout << "sum(int, int) is called" << endl;
    return x + y;
}
float sum(float x, float y)
{
    cout << "sum(float, float) is called" << endl;
    return x + y;
}
double sum(double x, double y)
{
    cout << "sum(double, double) is called" << endl;
    return x + y;
}

// //Is the following definition correct?
// double sum(int x, int y)
// {
//     cout << "sum(int, int) is called" << endl;
//     return x + y;
// }

int main()
{

    cout << "sum = " << sum(1, 2) << endl;
    cout << "sum = " << sum(1.1f, 2.2f) << endl;
    cout << "sum = " << sum(1.1, 2.2) << endl;

    //which function will be called?
    cout << "sum = " << sum(1, 2.2) << endl;

    return 0;
}

于老师课上讲的两个例子

• 一个是函数名相同，输入参数相同，返回参数不同，这个就是函数重定义，编译器报错。
• 另一个例子是当参数类型不同的时候，如果有多个函数，编译器会报错。但如果只有一个函数，不报错。

point

函数重载可以减轻程序员的记忆负担。