Hi all:
I have defined the template
template<class T>
class CGroup {
friend std::ostream & operator<<( std::ostream &lhs, const CGroup
&rhs );
private:
int nSize;
public:
std::deque<T> c;
};
Then, I define a group of people
CGroup<TPerson> myGroup;
where the person structure is defined as
struct TPerson {
int ID;
};
My question is: How do I define operator<< for CGroup in this case? Can
I add athe << operator to TPerson?
Thanks for your help,
Cuneyt 5 3985
cuneyt wrote: I have defined the template
template<class T> class CGroup { friend std::ostream & operator<<( std::ostream &lhs, const CGroup &rhs ); private: int nSize; public: std::deque<T> c; };
Then, I define a group of people
CGroup<TPerson> myGroup;
where the person structure is defined as
struct TPerson { int ID; };
My question is: How do I define operator<< for CGroup in this case?
What do you mean by "how"? What do you need it to do?
Can I add athe << operator to TPerson?
There is nothing that says you mustn't. As to whether you _can_,
I don't know. Can you? Just add it and see what happens.
V
Your "friend" declaration is wrong. As CGroup is a template, the stream
operator also has to be a template.
First declare your class as a template thus:
template < typename T > class CGroup;
Then declare the stream function as a template function:
template < typename T >
std::ostream & operator << ( std::ostream& os, const CGroup & rhs );
Now in your class CGroup add in an extra <> thus:
template < typename T >
class CGroup
{
friend std::ostream & operator<< <> ( std::ostream & lhs, const
CGroup & rhs );
// rest of CGroup
};
Now you can define your stream operator too. (Could not do so earlier
as CGroup was incomplete).
You can stream the T. If there is no overload for the T the compiler
will let you know.
Thanks for the replies. I think my main problem is that although I know
how the define the stream operator for classes, I cannot add it to
structures. For example, when I try
struct TPerson {
int ID;
std::ostream& operator<<( std::ostream &lhs, const TPerson &rhs );
};
the compiler gives the error: binary 'operator <<' has too many
parameters
Cuneyt
cuneyt wrote: Thanks for the replies. I think my main problem is that although I know how the define the stream operator for classes, I cannot add it to structures. For example, when I try
struct TPerson { int ID; std::ostream& operator<<( std::ostream &lhs, const TPerson &rhs ); };
the compiler gives the error: binary 'operator <<' has too many parameters
You need to understand that operator<< with a stream as its first argument
cannot be a _member_ of your class. It _could_ be a member of the stream
class, but since you can't modify 'std::ostream', you need to define your
operator<< as a _non-member_, i.e. _outside_ of the struct.
V
This is the declaration of the stream:
template < typename T >
std::ostream & operator << ( std::ostream& os, const CGroup< T > & rhs
);
I missed out the < T >.
It should be declared and defined (later on) outside of the class.
Inside the class you declare it as a friend. This thread has been closed and replies have been disabled. Please start a new discussion. Similar topics |
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