C auto decltype template-CodePudding

template<class T>
class P_STL
{
public:
    void print(T &t)
    {
        for (mit = t.begin();mit != t.end();mit  )
        {   
            cout << *mit << endl;
        }
    }
private:
    //T::iterator mit;          //error
    //auto mit = T().begin();   //error
    decltype(T().begin()) mit;  //OK
};

Code with c 11,I want to know: 1、What's 'T()',Why it can be used? 2、Why 2nd error happened? 3、Why 2nd error will be ok with decltype?

Hope some answers

CodePudding user response：

I think 1 should work but you need typename T::iterator. 2: I don’t think you can use auto like that in this context. This works better if you provide the errors you got.