在C ++中，operator []()是否必须为成员函数? [英] In C++, must operator[] () be a member function?

问题描述

在C ++中，operator []()是否必须始终是成员函数?如果是，为什么?

In C++, must operator []() always be a member function? If yes, why?

我在书中读了运算符必须是成员函数"

I read "An operator must be a member function" in book

"C ++编程语言特别版"第287页.

"The C++ Programming Language Special Edition" page 287.

推荐答案

来自C ++草案:

13.5.5下标[over.sub]

13.5.5 Subscripting [over.sub]

operator []应该是具有一个参数的非静态成员函数.它实现了下标语法

operator[] shall be a non-static member function with exactly one parameter. It implements the subscripting syntax

postfix-expression [表达式]

postfix-expression [ expression ]

因此，如果存在T :: operator且如果重载解析机制将运算符选择为最佳匹配函数，则将下标表达式x [y]解释为类型T的类对象x的x.operator. .3).

Thus, a subscripting expression x[y] is interpreted as x.operator for a class object x of type T if T::operator exists and if the operator is selected as the best match function by the overload resolution mechanism (13.3.3).

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我在规范中找不到它，但是我假设原因是因为它预期会返回一个左值.

从头开始:这没有道理.它返回下标类型的左值，而不是对象类型.

Scratch that: it didn't make sense. It returns an lvalue of the subscripted type not the object type.

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