在下面的代码中，我尝试特化类 A对于模板参数 T 时的基本情况具有值(value) B<m> .
#include <array>
#include <iostream>
template <std::size_t m>
struct B
{
std::array<double,m> arr;
};
template <std::size_t n, typename T>
struct A
{
std::array<T,n> arr;
const static int inner_dim = T::inner_dim;
};
template <std::size_t n >
template <std::size_t m>
struct A<n,B<m>>
{
std::array<B<m>,n> arr;
const static int inner_dim = m;
};
int main(int argc, char *argv[])
{
A<5,A<4,B<3>>> a;
std::cout << a.inner_dim << std::endl;
A<5,B<4>> b;
std::cout << b.inner_dim << std::endl;
return 0;
}
但是，在 main 中的实例化中，当我使用 g++ 5.4 编译时出现以下错误:
$ g++ -Wall --std=c++11 specialization.cc
specialization.cc: In instantiation of ‘const int A<4ul, B<3ul> >::inner_dim’:
specialization.cc:15:20: required from ‘const int A<5ul, A<4ul, B<3ul> > >::inner_dim’
specialization.cc:30:18: required from here
specialization.cc:15:20: error: ‘inner_dim’ is not a member of ‘B<3ul>’
const static int inner_dim = T::inner_dim;
^
specialization.cc: In instantiation of ‘const int A<5ul, B<4ul> >::inner_dim’:
specialization.cc:33:18: required from here
specialization.cc:15:20: error: ‘inner_dim’ is not a member of ‘B<4ul>’
似乎只使用了一般定义，从未使用过特化。如何确保实例化正确的特化？
最佳答案
我的猜测是
template <std::size_t n >
template <std::size_t m>
struct A<n,B<m>>
应该是
template <std::size_t n, std::size_t m>
struct A<n,B<m>>
关于c++ - 模板特化的不正确实例化，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/42087372/