== 运算符的含义是什么？

Looking into some code of a colleague of mine, I came accross the following:

看一下我的同事的一些代码,我得到了以下内容:

friend bool operator==<>(ValueIter<Type> const &rhs, ValueIter<Type> const &lhs);

It is declared in a template class:

它在模板类中声明:

template<typename Type>
class ValueIter: public std::iterator<std::bidirectional_iterator_tag, Type>

Can someone tell me what the ==<> symbol indicates? I expect it has something to with the != operator.

有人能告诉我== <>符号表示什么?我希望它与!=运算符有关。

3 个解决方案

#1

It looks like two, the operator== that is a full template instantiation or specialisation <>.

它看起来像两个,operator ==是一个完整的模板实例化或专门化<>。

I've seen only a few like this in the wild though.

我在野外只看到过这样的一些。

Given the friend, the class is probably befriending the template operator.

鉴于朋友,该类可能与模板操作员保持联系。

If you are getting linker errors with it, see this answer for why.

如果您遇到链接器错误,请参阅此答案以了解原因。

#2

Your question is incomplete.

你的问题不完整。

Presumably, in some context within the code you are examining, there is a templated operator==() function.

据推测,在您正在检查的代码中的某些上下文中,有一个模板化的运算符==()函数。

Then within some class, a particular specialisation of that templated operator==() is being declared as a friend.

然后在某个类中,该模板化运算符==()的特定特化被声明为朋友。

Without context that you haven't given (i.e. of the preceding template definition, or of the enclosing class definition) it is not possible to give a more specific answer. There are too many possibilities for what the template or relevant specialisations are.

如果没有您没有给出的上下文(即前面的模板定义或封闭类定义),则无法给出更具体的答案。模板或相关专业化的可能性太多了。

#3

With

template <typename T> class ValueIter;

template <typename T> 
bool operator==(ValueIter<T> const &rhs, ValueIter<T> const &lhs);

Inside template <typename T> class ValueIter

内部模板类ValueIter

friend bool operator==(ValueIter const &rhs, ValueIter const &lhs);
and friend bool operator==(ValueIter<T> const &rhs, ValueIter<T> const &lhs);
add friendship to a non template operator.

friend bool operator ==(ValueIter const&rhs,ValueIter const&lhs);和朋友bool operator ==(ValueIter const&rhs,ValueIter const&lhs);将友谊添加到非模板运算符。
friend bool operator==<>(ValueIter const &rhs, ValueIter const &lhs);,
friend bool operator==<>(ValueIter<T> const &rhs, ValueIter<T> const friend bool operator==<T>(ValueIter const &rhs, ValueIter const &lhs);,
friend bool operator==<T>(ValueIter<T> const &rhs, ValueIter<T> const
add friendship to the template operator (just for the type with match T)

friend bool operator == <>(ValueIter const&rhs,ValueIter const&lhs);, friend bool operator == <>(ValueIter const&rhs,ValueIter const friend bool operator == (ValueIter const&rhs ,ValueIter const&lhs);, friend bool operator == (ValueIter const&rhs,ValueIter const为模板运算符添加友谊(仅适用于匹配T的类型)
template <typename U> friend bool operator==(ValueIter<U> const &rhs, ValueIter<U> const &lhs); add friendship to the template operator (for any type U (which may differ of T))

template friend bool operator ==(ValueIter const&rhs,ValueIter const&lhs);将友谊添加到模板运算符(对于任何类型U(可能不同于T))

==<> is used in the second point and is really == <>.

== <>用于第二点,实际上是== <>。

#1