Thread: Stuck with friend functions and class template

Hi,
How do you do? I need to declare a friend function to my class... okay Let me post my code

Code:

template <typename T,int N> class MySequence;

template <typename T,int N>
bool operator==(const MySequence<T,N>&, const MySequence<T,N>&);

template <typename T,int N> class MySequence

{
friend bool operator== <T> (const MySequence<T,N>&,
const MySequence<T,N>&);
 
// my members and other methods
 };

bool operator== (const MySequence<T,N>& lhs,
const MySequence<T,N>& rhs)
 {
return lhs.value==rhs.value;
 }

Well the above code works fine. Now the thing is when I compare...

Code:

MySequence<int,10> ints;
MySequence<double,10> ds;

when write

Code:

if(ints==ds)
{
//some stuff
}

the compiler throws error because both are different objects.
But the comparison as shown below works fine

Code:

MySequence<int,10> ten_ints;
MySequence<int,2>   two_ints;

if(ten_ints==two_ints)
{
//some stuff
}
else
{
//do something
}

So I commented my friend function and incorporated operator overloading in the class itself

Code:

template <typename T,int N> class MySequence
{
/*friend bool operator== <T> (const MySequence<T,N>&, 
const MySequence<T,N>&);*/
public:

//some  methods
template <typename T2,int N2> 
 bool operator==(const MySequence<T,N>& lhs,
const MySequence<T2,N2>& rhs)
 {
      
return lhs.value==rhs.value;
 }
private:
//members
};

well the above works fine now i.e. I am able to compare int instance with double instance. But Is there a way to do it using friend functions?

Thanks in advance
-srikrish

Hi,
Thanks for the reply. I already did what you said,
the thing is how am I going to tell my class that this function is the friend.
I tried to put the following inside the class

Code:

friend bool operator== <T,E,N,M>(const MySequence<T,N>&,const MySequence<E,M>&);

and my compiler yells the error

Code:

error: ‘E’ was not declared in this scope
   friend bool operator== <T,E,N,M>(const MySequence<T,N>&,const MySequence<E,M>&);

I also tried placing

Code:

friend bool operator== <T,E>(const MySequence<T,N>&,const MySequence<E,M>&);

but never worked. So I resorted to overloading operator inside the class itself (as a method) and it worked.

Sorry for asking so many questions, just stared learning programming a few weeks back.

Thanks & Regards,
srikrish

Hi,
Sorry for replying late. Thanks for the response.
-Sridhar