C ++中可变参数个数？ [英] Variable number of arguments in C++?

问题描述

如何编写一个接受可变数目参数的函数？这是可能吗？

How can I write a function that accepts a variable number of arguments? Is this possible, how?

推荐答案

你可能不应该，你可以做一个更安全的事情和更简单的方式。技术上在C中使用可变数量的参数，包括stdarg.h。从中你将得到 va_list 类型以及操作它的三个函数 va_start（） code> va_arg（）和 va_end（）。

You probably shouldn't, and you can probably do what you want to do in a safer and simpler way. Technically to use variable number of arguments in C you include stdarg.h. From that you'll get the va_list type as well as three functions that operate on it called va_start(), va_arg() and va_end().

#include<stdarg.h>

int maxof(int n_args, ...)
{
    va_list ap;
    va_start(ap, n_args);
    int max = va_arg(ap, int);
    for(int i = 2; i <= n_args; i++) {
        int a = va_arg(ap, int);
        if(a > max) max = a;
    }
    va_end(ap);
    return max;
}

如果你问我，这是一团糟。它看起来不错，它是不安全的，它充满了与你在概念上试图实现无关的技术细节。相反，考虑使用重载或继承/多态，构建器模式（如在流中的 operator ）或默认参数等。这些都更安全：要更多地了解你想要做什么，有更多的场合，它可以阻止你，你吹你的腿之前。

If you ask me, this is a mess. It looks bad, it's unsafe, and it's full of technical details that have nothing to do with what you're conceptually trying to achieve. Instead, consider using overloading or inheritance/polymorphism, builder pattern (as in operator<<() in streams) or default arguments etc. These are all safer: the compiler gets to know more about what you're trying to do so there are more occasions it can stop you before you blow your leg off.

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