指向模板对象的指针

我无法编译...我不知道这里出了什么问题...这是发生错误的地方：

void MainThread::run()
{
    Set<int>* p_test; p_test = new Set<int>;
    p_test->add(new int(9));
    std::cout<<"The set is: {";
    for (int x = 0; x < p_test->size(); x++)
        std::cout<< ", " << p_test->toString(x).toStdString().c_str();
    std::cout<<"}";
    std::cin.get();
}//test method

错误消息给出为："对 Set：：Set（） 的未定义引用"，它显示在我尝试使用我的类的行上。我的类自己编译...下面是文件"Set.h"。有人知道我该如何解决它吗？提前谢谢。

#ifndef SET_H
#define SET_H
#include <functional>
#include <QList>
#include <QString>
#include <type_traits>
#include <exception>
#include <iostream>
template<typename T>
class Set {
public:
    //constructors
    Set();
    ~Set(){ delete []pType; }
    //functions
    const int & size(){ return m_size; }
    void add(const T * singleton);
    void empty();
    //operators
    inline T& operator [](int index){ return pType[index]; }
    template<class Y>
    friend Set<Y> operator *(const Set<Y>& s1, const Set<Y>& s2);//intersection
    template<class Y>
    friend Set<Y> operator *(Set<Y>& s1, Set<Y>& s2);
    template<class Y>
    friend Set<Y> operator +(const Set& s1, const Set& s2);//union
    template<class Y>
    friend Set operator -(const Set& s1, const Set& s2);//relative complement
    bool operator =(const Set& other)
    {
        delete []pType;//empty out the array
        /** Gets operator **/
        int x = other.size();
        pType = new T[x];
        for (int y = 0; y < x; y++)
            pType[y] = other[y];
        m_size = x;
        return true;
    }
    bool operator ==(const Set & other)
    {
        if(other.size() != size())
            return false;
        else
        {
            for (int x = 0; x < size(); x++)
                if (!other.has(pType[x]))
                    return false;
        }//end else
        return true;
    }//end equals operator
    /*template<typename Type>
    bool operator *= (const Set<Type> &lhs, const Set<Type> &rhs){
        //compile time statement (just to let people know)
        static_assert(std::is_same<Type1, Type2>::value, "Types are not equal!");
        return std::is_same<Type1, Type2>::value;
    }//operator for checking if two things are the same type */
    bool operator >(const Set &other)
    { /** Superset **/ return false; }
    
    bool operator <(const Set *other)
    { /** Subset **/ return false; }
    Set& complement();
    bool isEmpty(){ return m_size == 0; }
    bool has(T* element);
    QString toString(int index);
private:
    T * pType;
    T * m_Type; //save the variable type.
    int m_size;
};
#endif // SET_H

我确实在单独的文件中定义了一个构造函数。

Set<Y>::Set()
{
    m_size = 0;
    m_Type = new Y();//save a default value
}//create an empty set

还是我需要不同类型的构造函数？