Make Template for working program

[karatekid]

I made program that ask user to enter number to create an array. Then the array get sorted and the mean, median, and mode gets calculated. My problem is I get errors for templates for finding the mean, median and mode. I think I am doing template wrong. Can anyone help me make a template for finding the mean, median, and mode?

[hanst99]

I am pretty sure that for a method to be templated, the entire class would have to be templated as well (pretty sure means that I don't actually know for sure in this instance).

Either way, a template belongs in a header file - template classes and functions are instantiated at compile time, so you can't precompile a template and link it later on (you can precompile an instance of a template and link that later on though).

<int>Mode *mode= new Mode(a, size);

Would have to be

Mode<int> *mode= new Mode<int>(a,size);

Of course the class would have to be templated for that.

[karatekid]

I get an error
main.cpp:64: undefined reference to `Mode<int>::Mode(int*, int)'

[hanst99]

Why do you always post only like half of your class declaration? This isn't the first time you're doing this.

[karatekid]

Sorry

[zb0S216C]

*Frustratingly shouts* I thought you solved this? An undefined reference means that you're invoking a function that hasn't got a body. Define the body for Mode::Mode( int *, int ).

_Wazzak

[karatekid]

I did get this program to work, but now I have to create a template for finding the mean,median, and mode.

[zb0S216C]

Template definitions are simple. Here's an example one:

template < typename Type >
class Class
{
    public:
        Class( );

    private:
        int Member;

    public:
        int Method( );
};

// Definitions:
template < typename Type >
Class< Type >::Class( ) : Member( 0 )
{ }

template < typename Type >
int Class< Type >::Method( )
{
    return Member;
}

Try using the latter code as a guide.

_Wazzak

[hanst99]

And make sure the definitions appear in the header, not in some .cpp file.

[karatekid]

Do I have to template the whole class or can I just template a specific function like
get_Median(); get_Mean();?

Also did I create the object in Main.cpp correctly?
Mode<int> *mode=new Mode<int>(a,size);

[zb0S216C]

Yes. You created it correctly, AFAIK.

You can template a single method. It goes like this:

class Class
{
    public:
        template < typename Type >
        Type Method( Type );
};

// Definition:
template < typename Type >
Type Class::Method( Type Param )
{
}

_Wazzak

[karatekid]

I think I am doing it wrong.

[zb0S216C]

Don't place template definitions within source modules. Instead, declare the class along with its members. Then, define the body of each method underneath the class declaration, like I've done in my previous post.

_Wazzak

[ne555]

Also did I create the object in Main.cpp correctly?
Mode<int> *mode=new Mode<int>(a,size);

No, this ain't java.
Instead use Mode<int> mode(a,size);

[hanst99]

He did create it correctly. It is pretty pointless to do it that way if the Mode isn't supposed to persist past the function it was created in, but there was no syntactic or semantic error there.

[ne555]

He knows the type at compile time.
There is no persistence.
There is no copy overhead (container). the class could be lightweight
There is no polymorphism.
So I think it is a mistake to use a pointer there. (remember that you need to delete it)

The same applies to the b and m "arrays". Moreover you could have a double deletion because you didn't define the copy constructor and the assignment operator. You should use a std::vector there. (or 'destructive' methods)