Practical application cases of C++ variable parameters

Variadic functions allow functions to accept any number of parameters and can be used to handle an unknown number of inputs. For example, you can declare a function to calculate the maximum value in an array: declare the variadic function max, receiving an integer parameter num and variadic parameters .... Initialize the va_list variable args and receive variable parameters. Initialize the maximum value variable max_value to num. Use va_arg to iterate over the variable parameters and update max_value. Clean up va_list. Returns the maximum value.

Practical application cases of variable parameters in C

Variable parameters are a powerful feature in C that allow functions Accepts any number of arguments. This is useful when writing programs that need to process an unknown amount of input.

Grammar

The definition syntax of the variable parameter function is as follows:

return_type function_name(type param1, ..., type paramN, ...)
{
    // 函数体
}

Among them:

• return_type is the return type of the function.
• function_name is the name of the function.
• type is the type of variable parameter.
• param1, ..., paramN is an optional parameter list. Variable parameters must be placed last and can be represented by three dots ....

Actual case

The following is an actual case using variable parameters to calculate the maximum value in an array:

// 声明可变参数函数
double max(int num, ...)
{
    // 创建一个 va_list 变量接收可变参数
    va_list args;
    
    // 用 va_start 初始化 va_list，第一个参数为列表中第一个可变参数
    va_start(args, num);

    // 声明和初始化最大值变量
    double max_value = num;

    // 用 va_arg 访问每个可变参数，直到到达列表末尾
    while ((num = va_arg(args, int)) != 0)
    {
        // 更新最大值变量
        if (num > max_value)
            max_value = num;
    }

    // 用 va_end 清理 va_list
    va_end(args);

    // 返回最大值
    return max_value;
}

// 实例化可变参数函数
int main()
{
    // 使用可变参数函数计算数组中最大值
    int array[] = {3, 7, 2, 5, 1};
    size_t size = sizeof(array) / sizeof(int);
    double result = max(size, array[0], array[1], array[2], array[3], array[4]);

    // 输出结果
    cout << "数组中的最大值为: " << result << endl;

    return 0;
}

Output

数组中的最大值为: 7

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