如何在类型模板中调用值模板

Question

这个想法是为S类的特定函数提供编译时整数元素，用于不同的类型，例如S.

G ++不允许使用以下代码。谁能帮我解决这个问题？

template <class T, int s>
void fn1(T &t)
{
    t.fn2<s>();
}

struct S
{
    template <int s> void fn2 ()
    {
    }
};

void test()
{
    S s;

    fn1<S,3>(s);
}

导致：

$ g++ -c t.cpp
t.cpp: In function ‘void fn1(T&)’:
t.cpp:4:11: error: expected primary-expression before ‘)’ token
  t.fn2<s>();
           ^
t.cpp: In instantiation of ‘void fn1(T&) [with T = S; int s = 3]’:
t.cpp:18:12:   required from here
t.cpp:4:7: error: invalid operands of types ‘<unresolved overloaded function type>’ and ‘int’ to binary ‘operator<’
  t.fn2<s>();