可以切换operator+的边吗

Question

所以基本上我有一个“句子”类#includes“Word”。

句子是单词的链表

这是我的问题

"Word + Sentence 返回一个新的句子，其中单词添加到开头" 所以基本上

Word w = "The";
Sentence s = "dog jumped high."
//the object type of w+s should be a sentence

但是，我得到了错误，

'Sentence' does not name a type
//this is in reference to the return type of overloaded operator+ function, which is in the word class

那么有没有办法翻转 operator+ 重载的左右两侧，以便我可以将代码放入 Sentence 类中。

我无法将代码放在 Sentence 类中，因为我需要一个单独的重载函数

s+w 

返回一个在末尾添加单词的句子

Answer 1

在 C++ 中，运算符根本不必是成员。所以只需在你的类之外定义运算符：

Sentence operator+(const Word &word, const Sentence &sentence);

还请注意，您可以转发声明类：

class Sentence; // forward declaration

class Word {
    Sentence operator+(const Sentence &sentence) const;
};

class Sentence {
    ...
};

// Now that Sentence is defined (not just declared),
// you can define operator+ for Word (instead of just declaring it)
Sentence Word::operator+(const Sentence &sentence) const {
    ...
}