Template member function help.

**amparikh@gmail.com** · Oct 17 '06, 05:35 PM

Re: Template member function help.

Jason wrote:

/*
I have never use template before, so bear with me.
>
Here is what I am trying to do:
>
I declare an abstract base class MatrixInterface with template to
define an interface for all my subsequent Matrix class. In
MatrixInterface class, I overloaded the << operator by calling a pure
virtual function PrintDebugMessa ge(ostream &os); then I can implement
the function on individual Matrix classes later.
>
I create a Matrix class called SimpleMatrix, and implemented
PrintDebugMessa ge(). Everthing works great until I want to implement
different behavior depending whether it's
>
template<typena me DataTypevoid
SimpleMatrix<Da taType>::PrintD ebugMessage(... ); //this is fine
>
or
>
//error
template<typena me DataTypevoid SimpleMatrix< SimpleMatrix<Da taType>

::PrintDebugMes sage(...);

>
I want to print out data differently if a instance of my SimpleMatrix
is a collection of sub-matrices of type SimpleMatrix. However, I can't
get that to work.
>
If I sepcialize the template parameter like:
>
// works, but now only when submatrices has type of SimpleMatrix<in t>
template<void SimpleMatrix< SimpleMatrix<in t>

::PrintDebugMes sage(...);

>
then it works. How I generalize the function above to handle
SimpleMatrice submatrix of all type?
>
>
Below is a sample code of my problem. It compiles on gcc 3.2.3 and
intel c++ 8.1
*/
/*************** *************** **************
>
*************** *************** **************/
#include <iostream>
#include <typeinfo>
>
using namespace std;
>
/*************** *************** ******
** ABC for all Matrix class
*************** *************** *******/
template<typena me DataType>
class MatrixInterface
{
public:
template<typena me T>
friend ostream & operator<<(ostr eam &os, MatrixInterface <Tconst &
matrix);
protected:
virtual void PrintDebugMessa ge(ostream &os) const= 0;
>
};
>
template<typena me DataType>
ostream & operator<<(ostr eam &os, MatrixInterface <DataTypecons t
&matrix)
{
matrix.PrintDeb ugMessage(os);
return os;
}
/*************** *************** ******
** Simple Matrix
*************** *************** *******/
template<typena me DataType>
class SimpleMatrix:pu blic MatrixInterface <DataType>
{
public:
SimpleMatrix();
SimpleMatrix(si ze_t nrow, size_t ncol);
virtual ~SimpleMatrix() ;
protected:
>
virtual void PrintDebugMessa ge(ostream &os) const;
>
size_t m_rowSize, m_colSize;
DataType *m_data;
>
>
};
//
//
template<typena me DataType>
SimpleMatrix<Da taType>::Simple Matrix()
:m_rowSize(0), m_colSize(0),
m_data(0)
{
}
//
//
template<typena me DataType>
SimpleMatrix<Da taType>::Simple Matrix(size_t nrow, size_t ncol)
:m_rowSize(nrow ), m_colSize(ncol) ,
m_data(0)
{
if(m_rowSize*m_ colSize>0) m_data =new
DataType[m_rowSize*m_col Size];
}
//
//
template<typena me DataType>
SimpleMatrix<Da taType>::~Simpl eMatrix()
{
if(m_data != 0) delete [] m_data;
}
//
// Default PrintDebugMessa ge
//
template<typena me DataType>
void SimpleMatrix<Da taType>::PrintD ebugMessage(ost ream &os) const
{
size_t index;
cout << typeid(DataType ).name()<<"[ ";
for(index = 0; index < m_rowSize*m_col Size; ++index)
cout<<m_data[index]<<" ";
cout << "]";
}
>
/*!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!!
* I want PrintDebugMessa ge to behave differently
* when I when the m_data submatrice of type = SimpleMatrix<Tw here T
* can be anything.
*
* Doesn't work :(
*
!!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!*/
>
/*
template<typena me T>
void SimpleMatrix< SimpleMatrix<T: :PrintDebugMess age(ostream &os)
const
{
size_t index;
cout << typeid(SimpleMa trix<int>).name ()<<"[[[[ ";
for(index = 0; index < m_rowSize*m_col Size; ++index)
cout<<m_data[index]<<" ";
cout << "]]]]";
}
*/
>
>
/*!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!!
* This works. Don't really get it.
!!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!*/
template<>
void SimpleMatrix< SimpleMatrix<in t::PrintDebugMe ssage(ostream &os)
const
{
size_t index;
cout << "< "<<typeid(Simpl eMatrix<int>).n ame()<< " "<<"//** ";
for(index = 0; index < m_rowSize*m_col Size; ++index)
cout<<m_data[index]<<" ";
cout << "**//";
}
>
>
>
>
/*************** ***
*************** ***/
int main(int argc, char **argv)
{
SimpleMatrix<in tIntMatrix(3,3) ;
SimpleMatrix<do ubleDoubleMatri x(2,2);
SimpleMatrix< SimpleMatrix<in t IntMatrixMatrix (2,2);
SimpleMatrix< SimpleMatrix<do uble DoubleMatrixMat rix(2,2);
cout<<IntMatrix <<endl;
cout<<DoubleMat rix<<endl;
cout<<IntMatrix Matrix<<endl;
cout<<DoubleMat rixMatrix<<endl ; //use wrong Print function
return 0;
}

Well, you first need to either explicity partially specialize the class
for that type(SimpleMati rx<Tand then use PrintDebugMessa ge the way
you have used it.

Remember the class is a template class. PrintDebugMessa fe is NOT a
member template.

**amparikh@gmail.com** · Oct 17 '06, 05:35 PM

Re: Template member function help.

Jason wrote:

/*
I have never use template before, so bear with me.
>
Here is what I am trying to do:
>
I declare an abstract base class MatrixInterface with template to
define an interface for all my subsequent Matrix class. In
MatrixInterface class, I overloaded the << operator by calling a pure
virtual function PrintDebugMessa ge(ostream &os); then I can implement
the function on individual Matrix classes later.
>
I create a Matrix class called SimpleMatrix, and implemented
PrintDebugMessa ge(). Everthing works great until I want to implement
different behavior depending whether it's
>
template<typena me DataTypevoid
SimpleMatrix<Da taType>::PrintD ebugMessage(... ); //this is fine
>
or
>
//error
template<typena me DataTypevoid SimpleMatrix< SimpleMatrix<Da taType>

::PrintDebugMes sage(...);

>
I want to print out data differently if a instance of my SimpleMatrix
is a collection of sub-matrices of type SimpleMatrix. However, I can't
get that to work.
>
If I sepcialize the template parameter like:
>
// works, but now only when submatrices has type of SimpleMatrix<in t>
template<void SimpleMatrix< SimpleMatrix<in t>

::PrintDebugMes sage(...);

>
then it works. How I generalize the function above to handle
SimpleMatrice submatrix of all type?
>
>
Below is a sample code of my problem. It compiles on gcc 3.2.3 and
intel c++ 8.1
*/
/*************** *************** **************
>
*************** *************** **************/
#include <iostream>
#include <typeinfo>
>
using namespace std;
>
/*************** *************** ******
** ABC for all Matrix class
*************** *************** *******/
template<typena me DataType>
class MatrixInterface
{
public:
template<typena me T>
friend ostream & operator<<(ostr eam &os, MatrixInterface <Tconst &
matrix);
protected:
virtual void PrintDebugMessa ge(ostream &os) const= 0;
>
};
>
template<typena me DataType>
ostream & operator<<(ostr eam &os, MatrixInterface <DataTypecons t
&matrix)
{
matrix.PrintDeb ugMessage(os);
return os;
}
/*************** *************** ******
** Simple Matrix
*************** *************** *******/
template<typena me DataType>
class SimpleMatrix:pu blic MatrixInterface <DataType>
{
public:
SimpleMatrix();
SimpleMatrix(si ze_t nrow, size_t ncol);
virtual ~SimpleMatrix() ;
protected:
>
virtual void PrintDebugMessa ge(ostream &os) const;
>
size_t m_rowSize, m_colSize;
DataType *m_data;
>
>
};
//
//
template<typena me DataType>
SimpleMatrix<Da taType>::Simple Matrix()
:m_rowSize(0), m_colSize(0),
m_data(0)
{
}
//
//
template<typena me DataType>
SimpleMatrix<Da taType>::Simple Matrix(size_t nrow, size_t ncol)
:m_rowSize(nrow ), m_colSize(ncol) ,
m_data(0)
{
if(m_rowSize*m_ colSize>0) m_data =new
DataType[m_rowSize*m_col Size];
}
//
//
template<typena me DataType>
SimpleMatrix<Da taType>::~Simpl eMatrix()
{
if(m_data != 0) delete [] m_data;
}
//
// Default PrintDebugMessa ge
//
template<typena me DataType>
void SimpleMatrix<Da taType>::PrintD ebugMessage(ost ream &os) const
{
size_t index;
cout << typeid(DataType ).name()<<"[ ";
for(index = 0; index < m_rowSize*m_col Size; ++index)
cout<<m_data[index]<<" ";
cout << "]";
}
>
/*!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!!
* I want PrintDebugMessa ge to behave differently
* when I when the m_data submatrice of type = SimpleMatrix<Tw here T
* can be anything.
*
* Doesn't work :(
*
!!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!*/
>
/*
template<typena me T>
void SimpleMatrix< SimpleMatrix<T: :PrintDebugMess age(ostream &os)
const
{
size_t index;
cout << typeid(SimpleMa trix<int>).name ()<<"[[[[ ";
for(index = 0; index < m_rowSize*m_col Size; ++index)
cout<<m_data[index]<<" ";
cout << "]]]]";
}
*/
>
>
/*!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!!
* This works. Don't really get it.
!!!!!!!!!!!!!!! !!!!!!!!!!!!!!! !!!!!!!!!!!!*/
template<>
void SimpleMatrix< SimpleMatrix<in t::PrintDebugMe ssage(ostream &os)
const
{
size_t index;
cout << "< "<<typeid(Simpl eMatrix<int>).n ame()<< " "<<"//** ";
for(index = 0; index < m_rowSize*m_col Size; ++index)
cout<<m_data[index]<<" ";
cout << "**//";
}
>
>
>
>
/*************** ***
*************** ***/
int main(int argc, char **argv)
{
SimpleMatrix<in tIntMatrix(3,3) ;
SimpleMatrix<do ubleDoubleMatri x(2,2);
SimpleMatrix< SimpleMatrix<in t IntMatrixMatrix (2,2);
SimpleMatrix< SimpleMatrix<do uble DoubleMatrixMat rix(2,2);
cout<<IntMatrix <<endl;
cout<<DoubleMat rix<<endl;
cout<<IntMatrix Matrix<<endl;
cout<<DoubleMat rixMatrix<<endl ; //use wrong Print function
return 0;
}

Well, you first need to either explicity partially specialize the class
for that type(SimpleMati rx<Tand then use PrintDebugMessa ge the way
you have used it.

Remember the class is a template class. PrintDebugMessa ge is NOT a
member template.

**Victor Bazarov** · Oct 17 '06, 05:45 PM

Re: Template member function help.

Jason wrote:

/*
I have never use template before, so bear with me.
>
Here is what I am trying to do:
>
I declare an abstract base class MatrixInterface with template to
define an interface for all my subsequent Matrix class. In
MatrixInterface class, I overloaded the << operator by calling a pure
virtual function PrintDebugMessa ge(ostream &os); then I can implement
the function on individual Matrix classes later.
>
I create a Matrix class called SimpleMatrix, and implemented
PrintDebugMessa ge(). Everthing works great until I want to implement
different behavior depending whether it's
>
template<typena me DataTypevoid
SimpleMatrix<Da taType>::PrintD ebugMessage(... ); //this is fine
>
or
>
//error
template<typena me DataTypevoid SimpleMatrix< SimpleMatrix<Da taType>

>>>PrintDebugMe ssage(...);

[..]

What you're trying here is to specialise a member without specialising
the class first. That's prohibited, AFAIK.

Your solution lies either in specialising the entire class:

#include <iostream>
using namespace std;

template<class Tstruct Blah {
void out(ostream& os) {
os << "regular Blah\n";
}
};

template<class Tstruct Blah<Blah<T {
void out(ostream& os) {
os << "Blah of Blah\n";
}
};

int main()
{
Blah<intbi;
Blah<doublebd;
Blah<Blah<int bbi;
Blah<Blah<Blah< double bbbd;

bi.out(cout);
bd.out(cout);
bbi.out(cout);
bbbd.out(cout);
}

(which would require a whole lot of repetition) or in providing
a proxy "printer" class and specialising it instead (look up "policy
based design"):

#include <iostream>
using namespace std;

template<class Tstruct Blah;

template<class Tstruct Blah_Printer {
static void out(ostream& os, Blah<T>& blah);
};

template<class Tstruct Blah {
void out(ostream& os) {
Blah_Printer<T> ::out(os, *this);
}
};

template<class T>
void Blah_Printer<T> ::out(ostream& os, Blah<T>& b) {
os << "regular Blah\n";
}

// partial specialisation
template<class Tstruct Blah_Printer<Bl ah<T {
static void out(ostream& os, Blah<Blah<T& b) {
os << "Blah of Blah\n";
}
};

int main()
{
Blah<intbi;
Blah<doublebd;
Blah<Blah<int bbi;
Blah<Blah<Blah< double bbbd;

bi.out(cout);
bd.out(cout);
bbi.out(cout);
bbbd.out(cout);
}

Of course, 'Blah<Blah<Blah <Blah<Blah... >' is treated just like the
simply nested 'Blah<Blah<T' would be.

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

**Jason** · Oct 17 '06, 07:25 PM

Re: Template member function help.

On Oct 17, 10:58 am, "Victor Bazarov" <v.Abaza...@com Acast.netwrote:

Jason wrote:

/*
I have never use template before, so bear with me.

>

Here is what I am trying to do:

>

I declare an abstract base class MatrixInterface with template to
define an interface for all my subsequent Matrix class. In
MatrixInterface class, I overloaded the << operator by calling a pure
virtual function PrintDebugMessa ge(ostream &os); then I can implement
the function on individual Matrix classes later.

>

I create a Matrix class called SimpleMatrix, and implemented
PrintDebugMessa ge(). Everthing works great until I want to implement
different behavior depending whether it's

>

template<typena me DataTypevoid
SimpleMatrix<Da taType>::PrintD ebugMessage(... ); //this is fine

>

or

>

//error
template<typena me DataTypevoid SimpleMatrix< SimpleMatrix<Da taType>

>>PrintDebugMes sage(...);

[..]What you're trying here is to specialise a member without specialising

the class first. That's prohibited, AFAIK.
>
Your solution lies either in specialising the entire class:
>
#include <iostream>
using namespace std;
>
template<class Tstruct Blah {
void out(ostream& os) {
os << "regular Blah\n";
}
};
>
template<class Tstruct Blah<Blah<T {
void out(ostream& os) {
os << "Blah of Blah\n";
}
};
>
int main()
{
Blah<intbi;
Blah<doublebd;
Blah<Blah<int bbi;
Blah<Blah<Blah< double bbbd;
>
bi.out(cout);
bd.out(cout);
bbi.out(cout);
bbbd.out(cout);
}
>
(which would require a whole lot of repetition) or in providing
a proxy "printer" class and specialising it instead (look up "policy
based design"):
>
#include <iostream>
using namespace std;
>
template<class Tstruct Blah;
>
template<class Tstruct Blah_Printer {
static void out(ostream& os, Blah<T>& blah);
};
>
template<class Tstruct Blah {
void out(ostream& os) {
Blah_Printer<T> ::out(os, *this);
}
};
>
template<class T>
void Blah_Printer<T> ::out(ostream& os, Blah<T>& b) {
os << "regular Blah\n";
}
>
// partial specialisation
template<class Tstruct Blah_Printer<Bl ah<T {
static void out(ostream& os, Blah<Blah<T& b) {
os << "Blah of Blah\n";
}
};
>
int main()
{
Blah<intbi;
Blah<doublebd;
Blah<Blah<int bbi;
Blah<Blah<Blah< double bbbd;
>
bi.out(cout);
bd.out(cout);
bbi.out(cout);
bbbd.out(cout);
}
>
Of course, 'Blah<Blah<Blah <Blah<Blah... >' is treated just like the
simply nested 'Blah<Blah<T' would be.
>
V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask- Hide quoted text -- Show quoted text -

To Victor,

Thanks for the help! Your explanation clarify my confusion over
template.

Template member function help.

Template member function help.

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