如何定义提供指针深度/类型级别的模板类? [英] How can I define a template class which gives the pointer depth/level of a type?

问题描述

如何定义一个模板类，该类提供一个整数常量，该常量表示作为输入模板参数提供的(指针)类型的深度"?例如，如果该类名为Depth，则将满足以下条件:

How can I define a template class which provides an integer constant representing the "depth" of a (pointer) type provided as the input template argument? For example, if the class was called Depth, the following would be true:

Depth<int ***>::value == 3
Depth<int>::value == 0

推荐答案

template <typename T> 
struct pointer_depth_impl
{
    enum { value = 0 };
};

template <typename T>
struct pointer_depth_impl<T* const volatile>
{
    enum { value = pointer_depth_impl<T const volatile>::value + 1 };
};

template <typename T>
struct pointer_depth
{
    enum { value = pointer_depth_impl<T const volatile>::value };
};

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