操作符过载，允许使用右值捕获，但不分配给 [英] Operator overload which permits capturing with rvalue but not assigning to

问题描述

是否可以设计，以及如何对我的类 C 进行重载 operator +

Is it possible to design and how should I make overloaded operator+ for my class C to have this possible:

C&& c = c1 + c2;

但不可能：

c1 + c2 = something;

编辑：
我将对象更改为小写字母。 c1 ， c2 和 c c $ c> C 。 &&& 不是逻辑运算符&& ，而是一个右值引用。

I changed objects to small letters. c1, c2 and c are objects of class C. && is not the logical operator&&, but rather an rvalue reference.

例如：

double&& d = 1.0 + 2.0;

是100％正确的（新）C ++代码，而

is 100% proper (new) C++ code, while

1.0 + 2.0 = 4.0;

显然是一个编译器错误。我想要完全相同，而是双重，对于我的类 C 。

is obviously a compiler error. I want exactly the same, but instead for double, for my class C.

第二次编辑：
如果我的操作符返回C或C& amp;，我可以赋值为右值引用，但也赋值给c1 + c2，这是无意义的。 Giving const禁用它，但是它禁用赋值到右值。至少在VC ++ 2k10。

Second edit: If my operator returns C or C&, I can have assignment to rvalue reference, but also assignment to c1 + c2, which is senseless. Giving const here disables it, however it disables assignment to rvalue too. At least on VC++ 2k10. So how double does this?

推荐答案

赋值操作符只能在lvalue上调用：

Have the assignment operator be callable on lvalues only:

class C
{
    // ...

public:

    C& operator=(const C&) & = default;
};

请注意括号后的单个符号。它阻止分配到右值。

Note the single ampersand after the closing parenthesis. It prevents assigning to rvalues.

这篇关于操作符过载，允许使用右值捕获，但不分配给的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！