C ++多个继承自同名运算符 [英] C++ multiple inheritance off identically named operator

问题描述

是否可以从两个不同的抽象类继承名称相同的运算符，而该运算符的唯一区别是返回类型不同. 如果是这样，他们:

Is it possible to inherit identically named operator which only differ in return type, from two different abstract classes. If so, them:

• 实现运算符的语法是什么

• what is the syntax for implementing operators

使用/解析运算符的语法是什么

what is the syntax for using/resolving operators

在一般情况下，与任何其他虚函数一样，开销是多少?

what is the overhead in general case, same as for any other virtual function?

如果您可以为我提供参考或示例代码

if you can provide me with a reference or sample code that would be helpful

谢谢

12struct abstract_matrix {
 13    virtual double& operator()(int i, int j);
 14};
 15
 16    struct abstract_block_matrix {
 17        virtual double* operator()(int i, int j);
 18    };
 19
 20struct block_matrix : abstract_matrix, abstract_block_matrix {
 21
 22};

块矩阵需要为两个运算符提供实现，因此取决于上下文，它可以是矩阵，也可以是块矩阵.我不知道如何提供特定于block_matrix类的实现. 现在，这是通过传递对象包装类型作为最后一个参数来完成的，但这似乎不是很干净.我想保留纯矩阵符号.

block matrix needs to provide implementations for both operators, so that it is either a matrix or a block matrix, depending on the context. I do not know how to provide implementation specific to block_matrix class. right now, it is done by passing object wrapped type as the last argument, but that does not seem very clean. I would like to retain pure matrix notation.

推荐答案

函数的返回类型不是其签名的一部分，因此，block_matrix中不能包含两个operator +(i，j)-这将是一个模棱两可的电话.因此，就这一点而言，多重继承在某种程度上是一个红鲱鱼.你就是做不到.

The return type of a function is not part of it's signature, so you can't have two operator+(i,j)'s in block_matrix - that would be an ambiguous call. So multiple inheritance is sort of a red herring here on this point. You just can't do that.

您真正想做什么，为什么?

What are you really trying to do, and why?

无论如何，对于您的另一个问题:虚拟运算符在性能和操作方式方面与虚拟函数完全相同.在使用方式上，语义上仅有细微的差异-但实际上，它们的功能与其他任何功能一样.

In any event, for your other question: virtual operators are exactly like virtual functions in terms of performance and the way they operate. There are just slight semantic differences in how you use them - but under the hood they're just functions like any other.

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