如何将模板化结构/类声明为朋友?

2021-12-13 00:00:00 templates c++ friend

我想执行以下操作:

template <typename T>
struct foo
{
    template <typename S>
    friend struct foo<S>;

private:
    // ...
};

但我的编译器 (VC8) 卡住了:

but my compiler (VC8) chokes on it:

error C3857: 'foo<T>': multiple template parameter lists are not allowed

我想要所有 T 的 template struct foo 朋友的所有可能的实例化.

I'd like to have all possible instantiations of template struct foo friends of foo<T> for all T.

我该如何完成这项工作?

How do I make this work ?

这个

template <typename T>
struct foo
{
    template <typename>
    friend struct foo;

private:
    // ...
};

似乎可以编译，但正确吗?朋友和模板的语法非常不自然.

seems to compile, but is it correct ? Friends and templates have very unnatural syntax.

推荐答案

template<typename> friend class foo

然而，这将使所有模板彼此成为朋友.但我想这就是你想要的吗?

this will however make all templates friends to each other. But I think this is what you want?

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