问成员函数&常量成员函数指针推导

EN

template <class Ret>
class Foo
{
public:
    template <class T>
    void foo(T&, const std::function<Ret()>&)
    {
        std::cout << "std::function<Ret()>\n";
    }
    template <class T>
    void foo(T&, Ret(T::*)() const)
    {
        std::cout << "Ret(T::*)() const\n";
    }
    template <class T>
    void foo(T&, Ret(T::*)())
    {
        std::cout << " Ret(T::*)()\n";
    }
};

class A
{
public:
    void foo1() const
    {
    }
    void foo()
    {
    }
};

 int main()
 {

     A a;
     Foo<void> f;
     f.foo(a, &A::foo);
     f.foo(a, &A::foo1);
     f.foo(a, std::bind(&A::foo, a));
 }