From: daniel.kruegler@googlemail.com   
      
   On 2012-03-26 06:34, Ivan Godard wrote:   
   > Given:   
   > class A { private class B; ... };   
   > class A::B { public class C {...}; };   
   > std::ostream& operator<<(std::ostream&, const A::B::C&) {}   
   > There seems to be no combination of "friend" or other cleverness that   
   > will let the operator<< be declared.   
      
   What do you mean by "declared" in this context? I'm asking, because   
   an immediately defining friend function definition within A::B::C would   
   provide this feature.   
      
   > If you friend the operator into   
   > A::B it complains that A::B is private. If you friend it to A then it   
   > complains that A::B is undefined. You can't declare A::B before   
   > declaring A because you can't forward a nested type from an undefined   
   > class. You can't define the operator inside A::B because all the i/o   
   > operator are members of std::ostream and friends.   
      
   I have difficulties understanding your request, especially I don't   
   understand what precisely you mean by "If you friend the operator into   
   A::B" and similar notions.   
      
   > Is there any way to write an i/o operator for a nested class other than   
   > making the whole nest public?   
      
   Why doesn't this work for you:   
      
   #include    
      
   class A {   
   private:   
     class B;   
   };   
      
   class A::B {   
   public:   
     class C {   
       friend std::ostream& operator<<(std::ostream& os, const C& c)   
       {   
         // Output something   
         return os;   
       }   
     };   
   };   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
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