c++ - 模板 :Name resolution:Dependent template arguments : -->can any one tell some more examples for this statement?

Question

这是来自 ISO C++ 标准 14.6.2.4 的声明:依赖模板参数:

1. A type template-argument is dependent if the type it specifies is dependent.

2. An integral non-type template-argument is dependent if the constant expression it specifies is value dependent.

3. A non-integral non-type template-argument is dependent if its type is dependent or it has either of the following forms and contains a nested-name-specifier which specifies a class-name that names a dependent type.

4. A template template-argument is dependent if it names a template parameter or is a qualified-id with a nested-name-specifier which contains a class-name that names a dependent type.

我无法理解这些要点？

任何人都可以举例说明这些陈述吗？

Answer 1

这是我的理解。我已经根据 OP 中的行号标记了内联代码中的各个代码片段。

struct A{
    void f(){}
};

template<class T> struct B{};

// The template argument B<T> is TYPE depdent on the template parameter T                      (1)
template<class T, class U = B<T> > struct T1{};

// The template argument c is VALUE dependent on the template non type parameter 'c'        (2)
template<class T, char c, int d = c> struct T2{};

// The 2nd template argument is TYPE depdent on the template parameter T                    (3)
template<class T, void (T::*p)(void) = &T::f> struct T3{};

// The template template argument B is TYPE depdent on the template parameter T             (4)
template<class T, template<class U = T> class V = B> struct T4{};


int main(){
    T1<int> t1;
    T2<int, 'A', 2> t2;
    T3<A> t3;
    T4<A> t4; 
}