c++ - 模板<>（<> 中没有任何类 T）是什么意思？

Question

我正在阅读 stl_construct.h 中的一些源代码，在大多数情况下，它在 <> 中有一些东西，我看到一些只有“ template<> ...”的行。这是什么？

Answer 1

这意味着接下来是模板专业化。

Answer 2

Guess, I completely misread the Q and answered something that was not being asked.
So here I answer the Q being asked:

It is an Explicit Specialization with an empty template argument list.

When you instantiate a template with a given set of template arguments the compiler generates a new definition based on those template arguments. But there is a facility to override this behavior of definition generation. Instead of compiler generating the definition We can specify the definition the compiler should use for a given set of template arguments. This is called explicit specialization.

The template<> prefix indicates that the following template declaration takes no template parameters.

Explicit specialization can be applied to:

• Function or class template
• Member function of a class template
• Static data member of a class template
• Member class of a class template
• Member function template of a class template &
• Member class template of a class template

Answer 3

这是一个模板特化，其中所有模板参数都被完全指定，并且在<>.

例如：

template<class A, class B>   // base template
struct Something
{ 
    // do something here
};

template<class A>            // specialize for B = int
struct Something<A, int>
{ 
    // do something different here
};

template<>                   // specialize both parameters
struct Something<double, int>
{ 
    // do something here too
};