显示使用了正在定义的Cylinder<T>，应该怎么修改？

#include "stdafx.h"
#include<iostream>
#include<string>
using namespace std;
template <class T>
 class Cylinder
 {
 private:
Cylinder m_r,m_x,m_y,m_h,PI,V,S;
 public:
	 Cylinder(){m_r=0;m_x=0;m_y=0;m_h=0;PI=3;}
	 Cylinder(T r,T x,T y,T h){ m_r=r;m_x=x;m_y=y;m_h=h;}
	 Cylinder GetVolume() { return V=PI*m_r*m_r*m_h;}
	 Cylinder GetSurface(){ return S=2*PI*m_h*m_r+PI*m_r*m_r;}
friend ostream  &operator<<<T>(ostream &os, Cylinder &cyl)
	{
		os<<cyl.GetSurface()<<" "<<cyl.GetVolume();
    return os;
}
 };

 
 int main()
 {  Cylinder<int> a (1,1,1,1);

 cout<<a.GetSurface()<<"是圆柱体的体积"<<endl;
 cout<<a.GetSurface()<<"是圆柱体的表面积"<<endl;
 return 0;}

Cylinder m_r,m_x,m_y,m_h,PI,V,S;

Cylinder GetVolume() { return V=PI*m_r*m_r*m_h;}

Cylinder GetSurface(){ return S=2*PI*m_h*m_r+PI*m_r*m_r;}

以上几句感觉怪怪的。m_r,m_x,m_y,m_h,PI,V,S 应该是<T>， 返回的应该是泛型<T>。

还有你带参构造函数里面，PI也没有赋值。