friend ostream problem

This is a discussion on friend ostream problem within the C++ Programming forums, part of the General Programming Boards category; I have a class something like this Code: template class<T> class A{ private: T m; T n; List<T> *start; List<T> ...

  1. #1
    Registered User
    Join Date
    Dec 2009
    Posts
    5

    friend ostream problem

    I have a class something like this

    Code:
    template class<T>
    class A{
         private:
                    T m;
                    T n;
                    List<T> *start;
                    List<T> *end;
         public:
                    ...
                    friend ostream & operator<<(ostream &os, A<T> & dy);
    }

    Code:
    template class<T>
    ostream & operator<<(ostream &os, A<T> & dy)
    {
         os<<dy.start->x<<dy.start->y<<dy.start->value;
         return os;
    }
    x,y and value are some public elements of List<T>

    I do some operations on list and when I want to print the list elements , I wrote something like in implementation of operator<<, but i get segmentation error. How can i reach those x,y,and value in operator<< implementation?

  2. #2
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    23,787
    I note that the overload should be declared as:
    Code:
    friend std::ostream & operator<<(std::ostream &os, const A<T> & dy);
    That aside, the problem is probably with some other code, e.g., you forgot to initialise something, or you accessed something out of bounds, or you dereferenced a null pointer, etc.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
    Registered User
    Join Date
    Dec 2009
    Posts
    5
    yeah i think i make one of those, but for example when i write below in other functions
    Code:
    cout<<start->x<<start->y<<start->value;
    i get what i want ; but in operator<< implementation this does not work :S

  4. #4
    C++ Witch laserlight's Avatar
    Join Date
    Oct 2003
    Location
    Singapore
    Posts
    23,787
    Sorry, but there is just not enough information for me to help you. I suggest that you post the smallest and simplest compilable program that demonstrates the error.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  5. #5
    The larch
    Join Date
    May 2006
    Posts
    3,573
    From the looks of it, this should be relevant, but it is unclear why you don't get a linker error.
    I might be wrong.

    Thank you, anon. You sure know how to recognize different types of trees from quite a long way away.
    Quoted more than 1000 times (I hope).

  6. #6
    Registered User
    Join Date
    Dec 2009
    Posts
    5
    I do some stuff there to avoid linker errors
    how should i use this at there?

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Bin packing problem....
    By 81N4RY_DR460N in forum C++ Programming
    Replies: 0
    Last Post: 08-01-2005, 05:20 AM
  2. Words and lines count problem
    By emo in forum C Programming
    Replies: 1
    Last Post: 07-12-2005, 03:36 PM
  3. half ADT (nested struct) problem...
    By CyC|OpS in forum C Programming
    Replies: 1
    Last Post: 10-26-2002, 08:37 AM
  4. ostream problem...
    By Ruchikar in forum C++ Programming
    Replies: 3
    Last Post: 10-18-2002, 10:53 AM
  5. binary tree problem - help needed
    By sanju in forum C Programming
    Replies: 4
    Last Post: 10-16-2002, 05:18 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21