[問題]請問friend 跟template有關的問題

[richands (湛藍水色)]

程式碼(錯的那行)
friend ostream& operator << ( ostream& os , Stack<KeyType> &s);

錯誤顯示
[Warning] friend declaration `std::ostream& operator<<
(std::ostream&, Stack<KeyType>&)' declares a non-template function

[Warning] (if this is not what you intended, make sure the function
template has already been declared and add < > after the function
name here) -Wno-non-template-friend disables this warning

找好久都不知道錯誤所在   請問有高手可以幫忙嗎^^"

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推 khoguan:暫時凍結!請讀公告依板規將標題改得更具體明確。
※ 編輯: richands        來自: 220.132.113.85       (10/22 01:31)
推 khoguan:解凍
推 richands:Sorry
> -------------------------------------------------------------------------- <

作者: khoguan (Khoguan Phuann) 看板: C_and_CPP
標題: Re: [問題] 請問friend 跟template有關的問題
時間: Sat Oct 22 02:17:57 2005

※ 引述《richands (湛藍水色)》之銘言：
: 程式碼(錯的那行)
: friend ostream& operator << ( ostream& os , Stack<KeyType> &s);
: 錯誤顯示
: [Warning] friend declaration `std::ostream& operator<<
: (std::ostream&, Stack<KeyType>&)' declares a non-template function

  要嘛 operator<< 這個 friend function 也必需是 function template

  template <class KeyType>
  friend ostream& operator << ( ostream& os , Stack<KeyType> &s);

: [Warning] (if this is not what you intended, make sure the function
: template has already been declared and add < > after the function
: name here) -Wno-non-template-friend disables this warning

  不嘛，或是寫成

  friend ostream& operator<< <KeyType> ( ostream& os , Stack<KeyType> &s);

  或

  friend ostream& operator<< <> ( ostream& os , Stack<KeyType> &s);
  // 這樣寫較難看懂

  但常常仍需在 class 外部宣告一個 template operator<< function

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推 richands:感謝~ 問題已經解決  下次發文我會先注意的  抱歉^^"
→ richands:最後一段話    請問那邊要怎麼宣告呢?