The fullspecialization is no longer a template. It's a concrete function.
函数模板全特化后不再是一个模板， 它成为了一个函数的实现；
2
Is partial class specialization just a different way of writing a fullspecialization?
部分类专业化是一种不同的方式写一个完整的专业化?。
3
Each level of specialization has its own set of class attributes, which in the end provide the fullspecialization hierarchy for all specialized elements.