为什么要在 C++ 函数中最后添加默认参数?

问题描述

为什么要在 C++ 函数中最后添加默认参数?

Why should default parameters be added last in C++ functions?

推荐答案

为了简化语言定义并保持代码可读性.

To simplify the language definition and keep code readable.

void foo(int x = 2, int y);

要调用它并利用默认值，您需要这样的语法:

To call that and take advantage of the default value, you'd need syntax like this:

foo(, 3);

这可能让人觉得太奇怪了.另一种选择是在参数列表中指定名称:

Which was probably felt to be too weird. Another alternative is specifying names in the argument list:

foo(y : 3);

必须使用一个新符号，因为这已经意味着什么:

A new symbol would have to be used because this already means something:

foo(y = 3); // assign 3 to y and then pass y to foo.

ISO 委员会考虑并拒绝了这种命名方法，因为他们对在函数定义之外为参数名称引入新的意义感到不舒服.

The naming approach was considered and rejected by the ISO committee because they were uncomfortable with introducing a new significance to parameter names outside of the function definition.

如果您对更多 C++ 设计原理感兴趣，请阅读 The Design and Evolution ofC++ 来自 Stroustrup.

If you're interested in more C++ design rationales, read The Design and Evolution of C++ by Stroustrup.

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