creating base class (or whatever it is called) ?

[Craig Joyce]

Hi!,

I want to make a class that may do the following:

class T
{
......
}

int main()
{
T k = new T(3, 3);
/* k is now an array of 3, 3 integers */

k[2][1]=4; /* this is what I don't know how to do */
cout<<k[2][1];
return 0;

}

The trouble is that I don't know the keywords to search for to know
more about this. I thought 'base class' may be the way to describe
such a class so I posted it with the subject.
I hope someone helps this moron out,
-Craig

[Victor Bazarov]

"Craig Joyce" <na***********@ yahoo.com> wrote...

I want to make a class that may do the following:

class T
{
......
}

int main()
{
T k = new T(3, 3);
/* k is now an array of 3, 3 integers */

k[2][1]=4; /* this is what I don't know how to do */
cout<<k[2][1];
return 0;

}

The trouble is that I don't know the keywords to search for to know
more about this. I thought 'base class' may be the way to describe
such a class so I posted it with the subject.

What you need is to implement a class that overloads the indexing
operator (operator[]) so that "elements" could be accessed using
it.

class T
{
vector<vector<i nt> > storage; // where the elements are
public:
T(int w, int h);
vector<int>& operator[](int);
const vector<int>& operator[](int) const;
};

That's a minimalist interface your 'T' should probably have. You
get to fill the gaps.

Now, when you create it, you will have to probably create an object
without using 'new':

T k(3,3);

Victor

[Klaus Eichner]

"Craig Joyce" <na***********@ yahoo.com> wrote in message
news:7e******** *************** ***@posting.goo gle.com...

Hi!,

I want to make a class that may do the following:

class T
{
......
} // replace "class T {...}" by the following:
#include<vector >

int main()
{
T k = new T(3, 3);
// replace the above "T k = new T(3, 3);" by the following 4 lines:

std::vector<std ::vector<int> > k; // don't forget the extra space between
the two ">" ">"
k.resize(3);
k[0].resize(3);
k[1].resize(3);
k[2].resize(3);
/* k is now an array of 3, 3 integers */

k[2][1]=4; /* this is what I don't know how to do */
cout<<k[2][1];
// the above two lines work fine with std::vector<std ::vector<int> >
return 0;

}

The trouble is that I don't know the keywords to search for to know
more about this.
Although it is not immediately obvious, the keyword to search for (as far as
standard C++ is concerned) would be 'vector'.
I thought 'base class' may be the way to describe
such a class so I posted it with the subject.
There might exist a way in standard C++ to implement an array of 3, 3
integers using a base class, but this would probably be very complicated
compared to the std::vector<std ::vector<int> > solution.
I hope someone helps this moron out,
-Craig

[John Harrison]

"Craig Joyce" <na***********@ yahoo.com> wrote in message
news:7e******** *************** ***@posting.goo gle.com...

Hi!,

I want to make a class that may do the following:

class T
{
......
}

int main()
{
T k = new T(3, 3);
/* k is now an array of 3, 3 integers */

k[2][1]=4; /* this is what I don't know how to do */
cout<<k[2][1];
return 0;

}

The trouble is that I don't know the keywords to search for to know
more about this. I thought 'base class' may be the way to describe
such a class so I posted it with the subject.
I hope someone helps this moron out,
-Craig

Nothing to do with base classes, operator overloading and proxy classes are
what you want. In short you will overload the operator[] for T, to return a
proxy class which will also have the operator[] overloaded.

john