模板<>爲一個構件枚舉

Question

根據17.7.3 [temp.expl.spec]段落5（N4659）

... Members of an explicitly specialized class template are defined in the same manner as members of normal classes, and not using the template<> syntax. The same is true when defining a member of an explicitly specialized member class. However, template<> is used in defining a member of an explicitly specialized member class template that is specialized as a class template.

的E的顯式特絕對不屬於的顯式特大膽的情況下，它仍然需要template<>。這是爲什麼？

template<class T> struct A { 
    enum E : T; 
}; 

template<> enum A<int>::E : int { eint }; 

Answer 1

本段涉及明確專門化的類模板的成員，但是您沒有明確地專門化類模板。這是它在談論情況的一個例子：

template<class T> struct A { 
    enum E : T; 
}; 

template<> struct A<int> { 
    enum E : int; 
}; 

enum A<int>::E : int { eint }; // no template<> here 

在你的示例代碼，您已明確專門的主模板中的一員，這確實需要使用template<>，作爲第一款規定。

1 An explicit specialization of any of the following:

...

(1.7) — member enumeration of a class template

...

can be declared by a declaration introduced by template<>; that is: explicit-specialization: template < > declaration

第5段的基本原則是，一旦你明確專門的模板，它不再是一個模板，你與專業化就像你其他任何非模板實體工作。