模板类,功能专业化

Question

我想要一个看起来像我下面的模板类.然后,我想要一个带有模板特化的函数,具体取决于CLASS模板参数.我该如何工作？我意识到我提供的代码在很多层面都是错误的,但它只是为了说明这个概念.

template <typename _T, size_t num>
class Foo
{
    // If num == 1, I want to call this function...
    void Func<_T, 1>()
    {
        printf("Hi!");
    }

    // Otherwise, I want to call this version.
    void Func<_T, num>()
    {
        printf("Hello world!");
    }
};

Answer 1

struct Otherwise { };
template<size_t> struct C : Otherwise { };

// don't use _Uppercase - those names are reserved for the implementation
// (i removed the '_' char)
template <typename T, size_t num>
class Foo
{
public:
    void Func() { Func(C<num>()); }

private:
    // If num == 1, I want to call this function...
    void Func(C<1>)
    {
        printf("Hi 1!");
    }

    // If num == 2, I want to call this function...
    void Func(C<2>)
    {
        printf("Hi 2!");
    }

    // Otherwise, I want to call this version.
    void Func(Otherwise)
    {
        printf("Hello world!");
    }

    //// alternative otherwise solution:
    // template<size_t I>
    // void Func(C<I>) { .. }
};