Things to note about default parameters in C++ functions

Default parameters in C functions need to be noted: they must appear at the end of the parameter list. Multiple default values ​​cannot be specified for the same parameter. vararg A variable number of arguments cannot have a default value. Default parameters cannot be shared by parameters of overloaded functions.

Notes on default parameters in C functions

Introduction

Default parameters Allows you to omit certain parameters when calling a function. You can specify the default behavior of a parameter in a function definition by providing a default value.

Syntax

To declare a function with default parameters, follow the following syntax:

返回值类型 函数名称(参数1, 参数2 = 默认值, ...)
{
    // 函数体
}

Notes

When using default parameters, you need to pay attention to the following points:

• Default parameters must appear at the end of the parameter list.
• You cannot specify multiple default values ​​for the same parameter.
• A variable number of arguments called vararg cannot have a default value.
• Default parameters cannot be shared by parameters of overloaded functions.

Practical case

The following example shows how to use default parameters in a C function:

#include <iostream>

using namespace std;

// 计算圆的面积，圆心默认为 (0, 0)
double circleArea(double radius, double x = 0, double y = 0)
{
    return 3.14 * radius * radius;
}

int main()
{
    // 使用默认圆心计算面积
    double area1 = circleArea(5.0);
    cout << "Area with default center: " << area1 << endl;

    // 使用自定义圆心计算面积
    double area2 = circleArea(5.0, 2.0, 3.0);
    cout << "Area with custom center: " << area2 << endl;

    return 0;
}

Output:

Area with default center: 78.5
Area with custom center: 78.5

In the example, the circleArea function has three parameters: radius, x, and y. The x and y parameters have the default value 0, which means that if these parameters are omitted in a function call, 0 will be used.

We used the function with and without a custom circle center and printed the area. As you can see, using default parameters simplifies function calls without compromising flexibility.

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