Friend overloading of template classes

The friend overload of the template class and the friend overload of ordinary class are different, can refer to this CSDN blog http://blog.csdn.net/ozwarld/article/details/7770808

#include <iostream>using namespacestd; Template<classT>classTest;//template class predecessor declarationTemplate<classT>ostream&operator<< (ostream& out,Consttest<t>& obj);//template class friend predecessor DeclarationTemplate<classT>classTest { Public: Friend Ostream&operator<< <> (ostream& out,Consttest<t>& obj);//template class friend definition, note format "<>"Test (T n=0): num (n) {} Test (Consttest<t>&copy) {num=Copy.num; }    Private: T num;    }; Template<classT>ostream&operator<< (ostream& out,Consttest<t>&obj) {         out<<obj.num<<Endl; return  out; }    intMain () {Test<int> t (2); cout<<T; return 0; }    //Second Format#include<iostream>using namespacestd; Template<classT>classTest { Public: Template<classS>//Note <class s>sFriend ostream&operator<< (ostream& out,Consttest<s>&obj); Test (T n=0): num (n) {} Test (Consttest<t>&copy) {num=Copy.num; }        Private: T num;  }; //Note <class t> and <class s>.Template<classT>ostream&operator<< (ostream& out,Consttest<t>&obj) {               out<<obj.num<<Endl; return  out; }      intMain () {Test<int> t (2); cout<<T; return 0; }  

Friend overloading of template classes